Not a builder-grade 6-mil sheet held down with rocks. A real 20-mil reinforced polyethylene liner, mechanically fastened, taped at every seam, wrapped up walls and around piers. This is the moisture barrier that lasts 20+ years.
A licensed local crew — usually out in 24 to 72 hours. Written scope, fixed price, no pressure.
A man on Packard Avenue called me last spring and opened with a sentence I hear four or five times a season in this city: I do not want the whole program, I just want the plastic. He was seventy-one, he had lived in that house since he was in high school, his father worked at Plant One, and he had spent the previous month getting quotes that all came back describing a sealed crawlspace with equipment in it. He was not being difficult and he was not underinformed. He had looked under his own house with a flashlight, seen bare dirt, and reached a correct conclusion about the most obvious thing wrong down there. What he wanted was for somebody to price the obvious thing.
So that is what I did, and it is worth explaining what that job actually is, because the word barrier gets used loosely enough that people do not know what they are buying. Section R408.2 of the 2018 North Carolina Residential Code says that in a wall-ventilated crawlspace, the exposed ground has to be covered with an approved vapor retarder of at least six-mil polyethylene, with the joints lapped not less than twelve inches. That is the entire requirement. It is a ground retarder in a crawl that continues to breathe through its vents, and the code treats it as a different animal from the closed crawlspace assembly in R409, which is a sealed perimeter with a defined air boundary and a specified means of removing moisture. Two different sections, two different scopes, two different results. Confusing them is how an owner ends up either paying for a system he did not need or being told a liner will do something it cannot.
His crawl was a good candidate for the smaller scope and I will say why, because the reasoning is the useful part. Cartown houses sit on continuous concrete block perimeter with eight-by-sixteen vents, and his were open, screened and clear. The ground was dry to the touch across the whole footprint with no silt lines at the base of the walls, no staining, and no evidence in the debris pattern that water had ever moved through there. His gutters were intact and discharging away from the house, which is not something I get to write often. Moisture readings on the joists and the band came back in a range that told me the framing had never been in trouble. What he had was bare Piedmont clay under a floor and nothing else wrong. That is the exact case where a ground vapor retarder is the correct and complete answer, and where selling him anything more would have been dishonest.
Here is the mechanism, since the reason matters more than the material. Clay soil in the Piedmont holds water and moves it upward by capillary action toward the surface, and at the surface it evaporates into whatever air is sitting above it. That evaporation is not a trickle. Across a couple of thousand square feet of exposed dirt in a humid climate it is the dominant moisture source in most crawlspaces, and it runs continuously, day and night, all twelve months, because it is driven by the vapor pressure difference between wet soil and the air. A sheet of polyethylene over that soil does one thing and does it very well: it cuts the source off. Everything a liner accomplishes flows from that single fact, and everything a liner cannot accomplish flows from the fact that soil emission is not the only moisture source a crawlspace has.
That second half is the conversation I owe every person who calls asking for just the plastic. A ground retarder in a vented crawl cannot bring the air under your house drier than the air coming in through the vents. From May through September the outdoor air here carries more moisture per pound than the surfaces under your floor can tolerate, so if your ductwork is sweating in July, a liner will not stop it. If groundwater arrives after a heavy rain, a liner will have water on top of it or under it depending on where it comes from. If your floor is sagging, a sheet of poly has no opinion about that. And the humidity number you read on a gauge in August will improve, sometimes noticeably, but it will not drop into the range people have read about, because that range belongs to a sealed and dehumidified space and not to a vented one.
On Packard Avenue none of those limits were binding, which is why the smaller scope was the right scope. He got a properly prepared ground, a continuous retarder detailed to and past the code minimum, his vents cleaned out and rescreened, and a walk around the outside with me pointing at the one downspout that needed extending. He did not get equipment he would have had to maintain, and he did not get a sealed perimeter on a house that had no complaint the seal would have answered. I put the limits in writing along with the scope, including the sentence about August, so that if he calls me in three years about a humidity reading, neither of us has to relitigate what he was told. That is what an honest version of this job looks like.
The question he asked at the end is the one I want to answer here at the top, because it holds a lot of people up. He wanted to know whether spending money on a ground cover now would be money thrown away if he ever decided to go further. The answer depends on how the work is done and on nobody being cute about it. A ground retarder installed as a ground retarder is not a partial sealed crawl and it is not a down payment on one; if that house is ever converted, the perimeter work, the vent closures, the mechanical means of removing moisture and, realistically, the liner itself all get done then, because the heavier membrane a sealed assembly needs is a different product bought for a different job. What the smaller scope buys you is the actual benefit it can deliver, for as long as the house stays vented, which in most of this city is indefinitely. It is a complete answer to one problem rather than a fragment of an answer to a larger one, and it should be sold and priced and explained that way.
Vapor barrier work in Kannapolis is dominated by what is already under these houses: on the Cannon-era village grid in North Kannapolis, Cartown, Centerview and Jackson Park, forty-plus years of owner-era ground cover since the 1982 Murdock sell-off has usually meant a scrap of thin polyethylene folded double over half the dirt; in the 1970s to 1990s tract off Royal Oaks and Forest Park, the builder six-mil has been in the ground three or four decades and torn by every service call.
Cannon-era village frame house on East 22nd, West A or West 7th where the previous owner laid a scrap of 4-mil poly loose over part of the dirt, folded double in two places, and it is now holding water against the ground where it doubles instead of shedding it
Post-war brick ranch in Royal Oaks along Alabama, Dakota or Tennessee Street with the original 1975 builder 6-mil in the ground — torn from every plumbing and HVAC service call over 50 years and no continuous ground cover at any of the piers
Cartown block along Chevrolet, Cadillac or Packard with 14-to-20-inch clearance — full 20-mil reinforced rolls will not turn inside the space, so the liner comes in as smaller cut pieces with more seams that all have to be bonded properly with Polyken 337 or Nashua 357 double-sided between the sheets
Kellswater Bridge or Kannapolis Parkway 2000s subdivision house where builder poly runs six inches up the block on adhesive that has let go after five summers, the wall termination is on the ground, and the top of the assembly is completely open to whatever the crawl is doing
Granite-belt house east toward Faith, Rockwell or Granite Quarry on Balfour Pink piers where the exposed rock and gravel between the stones has been slicing every liner ever installed, and the ground preparation has to include covering or removing the sharp fragments before rolling
Village house with 14-plus brick pier stacks along Ridge, Rose or West Harding — every pier is a wrap and the previous liner stopped six inches short of each column, leaving 14 exposed rings of soil at exactly the points that are hardest to reach later
The reason a bare dirt floor matters so much in this city comes down to surface area and time. A crawlspace under a modest one-story house is on the order of a thousand square feet of exposed soil, sitting inches below a wood floor system, and every square inch of it is evaporating continuously. There is no season when it stops. In a Piedmont clay the water is being drawn upward faster than the surface can dry, so the surface stays effectively saturated and the evaporation rate stays near its maximum. That is a steady, relentless input, and it is the reason a crawl that gets a fresh liner shows a change within days rather than weeks. You did not remove any water from the space. You disconnected the tap.
Capillary rise is worth understanding because it explains why the surface never simply dries out on its own. Fine-textured soils move water upward through the pore network against gravity, and the finer the texture the further it climbs. Piedmont clays are fine textured by definition, which is why you can dig down eighteen inches under a Kannapolis crawl in September, after weeks without meaningful rain, and pull out spoil that is visibly damp. The dry-looking crust on top is a few millimeters deep and it is not a seal. Scrape it and the material underneath is wet. That is the reservoir a ground retarder is placed between you and, and it is also why the argument that a crawl looks dry so it must be fine does not hold up.
Now the limit, stated as precisely as I can make it, because the honest boundary of this service is the most valuable thing on this page. A wall-vented crawlspace exchanges air with the outdoors continuously through its vent openings. Whatever moisture the outdoor air is carrying, that air comes in and brings it. Cover the ground perfectly and you have removed the soil contribution entirely, and what remains is outdoor air plus whatever leaks down from the house. So the floor under your vented crawl is the outdoor absolute humidity, and no ground retarder ever made can take you below it. In Kannapolis the outdoor relative humidity runs generally in the seventy to seventy-six percent band with the August peak near seventy-four, and roughly forty-four to forty-eight inches of rain falls on this ground every year to keep it that way. Those are the numbers a liner has to live inside.
That limit is not the same in every season, and the seasonal shape of it is what makes a ground retarder genuinely worthwhile rather than merely code compliance. From roughly October through April the outdoor air is drier in absolute terms than the air a bare crawl generates for itself, so ventilation is actively helping and the soil is the thing holding the space back. Cover the soil in that period and the vents do the rest, and a properly liner-ed vented crawl in a Kannapolis January is a genuinely dry space. From May into September the relationship inverts, the incoming air becomes the dominant moisture source, and the best a liner can do is stop making the situation worse. Cutting the soil contribution during the months when the crawl also has the most incoming load is still meaningful, and on a well-drained house it is often the difference between framing that sits in a safe moisture range and framing that does not.
There is a second effect that gets overlooked and it has nothing to do with humidity readings. Bare soil in a crawlspace is a surface that people and animals and water all interact with. It generates dust that moves up into the house through the floor along with the air. It supports growth on anything organic lying on it, and there is always something organic lying on it in a house that has been occupied since the 1930s. It gives insects and rodents an interface. And it makes every trade that has to work under there, from a plumber to a pest inspector to me, less willing to do a thorough job, which sounds soft until you have watched somebody decide not to crawl the last fifteen feet. A clean, continuous surface changes the behavior of everyone who goes under the house, and that has a real effect on how well the house gets looked after over decades.
Finally there is what the liner is protecting, which in the older Kannapolis stock is not replaceable. The framing under a Cannon-era village house is old-growth material that nobody is milling anymore, and it has survived a hundred and ten years partly because these crawls, for all their faults, were shallow and reasonably open. What kills that wood is sustained elevated moisture content, not a wet week. Framing that equilibrates around fifteen or sixteen percent through a summer is fine and will be fine in another fifty years. Framing that sits above that year after year is on a trajectory that ends in a repair. A ground retarder is the single cheapest intervention available in terms of effort and disruption that moves that number in the right direction, and on a house that does not have a water problem or a ventilation problem, it may be the only intervention that number needs.
There is one more thing exposed soil does that belongs on this page even though it is outside what I am licensed to certify, and I would rather raise it than let somebody discover it later and feel misled. Bare ground is an open pathway for whatever gas the soil is producing to enter the space under your floor, and from there some fraction of it follows the same route into the house that everything else under there follows. Piedmont geology is variable enough on this question that the only honest statement about any individual address is that it has not been tested. A continuous sheet, laps bonded and edges detailed, measurably reduces that pathway and it is a reasonable side benefit to expect. What it is not is a control system, because a control system is a designed sub-membrane suction path with a fan and a monitored result, and that is a different trade with its own certification. If you want to know your number, a test kit is inexpensive and widely available. If the number comes back high, tell me before I install, because the liner detailing is done differently when it may later have to serve as a membrane for a mitigation system, and doing it in that order costs nothing extra while doing it in the other order means opening the sheet back up.
Same steps every job. No shortcuts.
measure the crawlspace footprint including any added-on shed rooms or enclosed back porches that have their own crawl at a different level, check the standing water pattern and existing barrier condition, and count the piers because every one is a wrap in the scope
vapor barrier install alone is generally not a permitted scope, but any scope that includes drainage trenching, a sump basin, structural work, or crawlspace mechanical goes through Cabarrus County Construction Standards at 65 Church St S Suite 280, 704-920-2128 on ACCELA for parcels inside the Kannapolis city limits including the Rowan-side blocks; outside city limits on the Rowan side, Kannapolis Planning zoning at 401 Laureate Way 704-920-4350 first, then Rowan County Building Inspections at 402 N Main St Room 207 in Salisbury 704-216-8619 through EnerGov
clear organic debris including construction rubble from the 1907-1940s original build, coal clinker and brick fragments on the village houses, and any sharp granite fragments on the Faith, Rockwell and Granite Quarry lots; grade low spots that hold water either out or deliberately to a single low point where a basin could be placed later
20-mil reinforced woven polyethylene from Americover, Viper CS or YellowGuard rather than a 6-mil sheet, cut to exact dimensions outside because a full roll will not turn inside a 14-to-20-inch village crawl through a 16-by-24 hatch
seams overlapped at least 12 inches per the code minimum for a ground retarder, bonded with Polyken 337 or Nashua 357 double-sided pressure-sensitive tape between the sheets rather than a strip laid on top, piers wrapped up the column with SikaFlex-1a at the top edge, wall run mechanically fastened to a termination bar rather than adhesive-glued on dusty block, and the top three inches of masonry left exposed for termite inspection access
so the next real estate transaction, home inspection or termite bond renewal has the documentation it needs and the assembly does not have to be trusted on somebody's word
Start with what the code actually sets as the floor, because everything else is a decision made on top of it. R408.2 requires an approved vapor retarder not less than six-mil polyethylene covering the exposed ground in a wall-vented crawlspace, with joints lapped not less than twelve inches. That is a minimum, not a specification, and the word approved is doing quiet work in that sentence. What it does not tell you is how the sheet is prepared for, how it is held down, how it is detailed at piers and obstructions, or how long it will last with people working on top of it. Two installations can both satisfy R408.2 and be nothing alike in five years.
On thickness I go up from the minimum on nearly every job, and I want to be precise about why rather than selling a number. Six-mil polyethylene is a perfectly good vapor retarder in the laboratory sense; its permeance is low and it does the physics. Where it fails is mechanically. It tears when a knee lands on a brick fragment, it punctures under a dropped tool, it splits along a fold, and it degrades where sunlight reaches it through a vent. A crawl is a serviced space, and over twenty-five years somebody will be down there for a water heater, a duct, a leak or a pest inspection. So my default is a ten or twelve mil sheet, string-reinforced where the traffic pattern warrants it, which survives that use. What I am not doing is quietly upgrading you into the twenty-mil reinforced membrane I use in a sealed assembly, because that heavier product is chosen for a different reason. In a closed crawl the liner is also the air barrier and the surface every other component terminates to, so it takes abuse from the assembly itself. In a vented crawl it is a ground cover, and specifying it as though it were structural is spending your money on the wrong problem.
Preparation is most of the labor and it is the difference between a liner that lies flat for decades and one that is torn in three places by the second year. Everything organic comes out first: leaf pack that blew in through the vents, cardboard, fallen insulation, and on the village houses a genuinely surprising volume of coal clinker, brick bats and construction leavings from 1907. Then the surface gets made fit for sheeting. Sharp masonry fragments and protruding stone get removed or covered. Abandoned pipe stubs and old plumbing get cut flush or capped. High spots that would stretch the sheet get knocked down and depressions that would pond get either filled or, better, deliberately connected so any water that ever does arrive has a route rather than a puddle. On the granite-belt jobs out toward Faith and Granite Quarry this stage takes longer than the liner itself, because rock that is close to grade cannot be removed and has to be worked around and padded.
Laps and seams get more attention than the code strictly demands, for a practical reason. Twelve inches of overlap is the requirement, and twelve inches of loose overlap in a space where air moves through the vents will lift and separate. I run the laps oriented so they shed toward the low point rather than against it, the way you would lap roofing, and I bond them rather than leaving them loose. For a ground-only retarder that generally means a double-sided pressure-sensitive tape between the sheets, Polyken 337 or Nashua 357, rather than a strip laid over the top of the joint where the first person to drag a bucket across it will roll it up. Around the perimeter and at the piers the sheet gets held rather than trusted to lie still, which in a vented crawl means ballast, spot fastening at the wall, or both, chosen for what the substrate will take.
Piers and columns are the fiddly part on a village house, where a footprint may have fourteen or more of them. Two approaches are legitimate and I pick per house. The sheet can be cut and fitted around each column and sealed to it, which gives complete ground coverage and is what I do where the columns are sound and reasonably regular. Or the sheet can be run to the column and dressed up onto it a few inches, which is faster and adequate where the column is irregular fieldstone that will not take a clean seal. What is not acceptable is a rectangle of poly with a hole in it and six inches of bare ground showing around every pier, which is what I usually find when somebody has done this themselves, and which in aggregate can leave a meaningful fraction of the soil still exposed.
Whether the sheet runs up the foundation wall is a real question and it is where this job most often drifts into being something else. In a vented crawlspace the code requirement is ground coverage, full stop. I do run the sheet up a short distance at the wall on most jobs, because a terminated edge stays put and a loose edge curls and gets kicked, but that is an installation detail rather than an air seal, and I say so plainly on the proposal. What I do not do on a vented job is carry material up to the sill, seal it continuously, and call it a barrier system. That covers the masonry band a termite inspector needs to read, it gives an owner the impression of a sealed crawl without any of the mechanism a sealed crawl requires, and it is the specific thing that makes people believe encapsulation does not work when what they actually received was a liner in costume.
The vents stay open and they get serviced, which is the other half of a wall-vented crawlspace and the half nobody quotes. Every opening gets cleared, the screening gets checked and replaced where it has rusted through, and any vent that has been foamed shut by a previous owner who read half an article gets opened back up unless we are deliberately converting to a closed assembly. Vent wells on the below-grade openings get cleaned out and, where the well is holding water against the foundation, addressed. In the West Brook and Wildwood blocks where mature canopy drops litter into every opening each autumn, I tell owners plainly that this is a fall chore now, because a crawl whose vents pack solid in October has been silently converted to an unventilated crawl right as the wet season starts.
Two things belong in the scope that are not liner at all, and on a well-designed ground-retarder job they are the items that determine whether the result holds. Gutters and downspouts get inspected and the discharge gets extended past the foundation, because roof water landing at the wall is the single most common reason a crawl that should be dry is not. Grade gets read at every elevation and negative grade gets corrected. On the flat, shallow-graded lots through Royal Oaks this is nearly always the highest-value part of the visit. Near the Kannapolis Lake buffer any regrading is constrained by the WS-III protected water-supply watershed and gets confirmed with the city first. Materials for all of this are ordinary and local: sheeting and tape come off the shelf from the regional houses, Ferguson on Biscayne Drive in the 28027 zip covers anything on the water side, Beacon Building Products on Florence St handles envelope material, and the Home Depot at Cloverleaf Plaza carries day-of consumables. None of it is a special-order wait.
And here is what deliberately is not in a ground vapor retarder scope, because leaving it out is a decision rather than an omission. No dehumidifier, because running one in a space that is open to the outdoors through a dozen vents is asking a machine to dry the neighborhood and it will run continuously and lose. No wall insulation, because the wall is not part of the thermal boundary in a vented crawl. No fiberglass going back into the joist bays; if it is already up there and it is wet or hanging, it comes out and it does not get replaced, because a batt that gets damp in a vented crawl holds water against the subfloor. No sealed vents. No sump basin unless there is genuine groundwater, in which case this was never the right scope in the first place. If a proposal contains a liner and a dehumidifier and the vents are staying open, somebody has combined two incompatible strategies and charged for both.
Access openings and interior divisions are where an otherwise good installation quietly loses its coverage, and they get named individually on the scope. The hatch or door sees more traffic than any other square yard down there, so the sheet gets an oversized, separately fastened panel at the landing zone rather than a lap that will be scuffed apart by the third visit. Where a crawl is split into compartments by an interior stem wall, which is common on the Kannapolis houses that gained a rear addition in the 1950s, each compartment is treated as its own footprint and the sheet is terminated at the dividing wall on both sides instead of being fed through the low opening between them, since a sheet dragged through a twelve-inch pass-through will not stay where you put it. Where the crawl steps down to meet a partial basement or a garage slab, the retarder stops at the change in construction and gets an edge, and I do not run it out onto a slab, which accomplishes nothing and traps whatever the slab is giving off. Duct trunks and plumbing runs that rest on the ground get lifted and supported first if they can be, and if they cannot, the sheet is cut and fitted to them rather than tucked underneath, because material under a pipe holds a channel of water for the life of the installation.
Almost none of the Cannon-era village houses in this city got a ground vapor retarder from the factory. That is not a criticism of how they were built; nobody was putting polyethylene under a mill house in 1907, and the shallow, well-vented crawls those houses were given worked reasonably well for their era. What it means practically is that if you own a house in the village grid and you have never had this done, you are standing on original 1907 dirt. Whatever is down there now was put there by an owner, and since the company houses were sold to the families living in them in 1982, that has generally meant a scrap of thin poly laid loose over part of the footprint by somebody working alone with a flashlight. It usually stops several feet short of the walls, has no laps to speak of, is folded double in places, and skips every pier. It is doing a fraction of what the owner believes.
The tract and post-war belts have the opposite history and a different problem. Through Royal Oaks, Forest Park, Shady Brook and the later blocks around Rainbow Drive and Klondale, builders did put six-mil down, and that sheeting has now been in the dirt for three or four decades. What thirty-five years does to a thin sheet in a serviced crawl is entirely mechanical: it is torn along every route anyone has taken to reach a water heater, it has separated at the laps, it has been pulled back and never replaced by whoever ran a new supply line in 1994, and where a vent has let sunlight onto it, it has gone brittle enough to crumble in your hand. The material has not stopped being a vapor retarder in the places it is still intact. There simply are not many of those places left.
Whether a ground retarder is the right and complete scope for a Kannapolis house comes down to what else the crawl is doing, and the city divides fairly cleanly. The well-drained blocks on the higher ground, the flat lots through Royal Oaks where the only water is roof water, the Cartown and Centerview houses with clear vents and sound perimeters, and a great deal of the village grid where the ground is simply bare and nothing else is wrong: those are liner jobs, and I would rather do that job properly than sell a system nobody needs. On the other side of the line is the Lake Fisher quadrant, where houses sit on lower landforms in the reservoir and Cold Water Creek drainage and the Iredell-type soils are somewhat poorly drained, so standing water under the floor is the normal condition rather than an event. A sheet of poly over ground that is delivering liquid water is not a solution to anything and I will not sell it as one.
The same disqualification applies in smaller doses in specific places rather than whole neighborhoods, and this is the reason I do not quote from a phone description. The East 10th through 13th Street blocks in Jackson Park fall toward the Irish Buffalo drainage and hold water at the low end of the crawl after sustained rain. Several West Brook blocks step down toward the Irish Buffalo headwaters and the low side stays wet. The western blocks of Centerview fall toward Cold Water Creek tributaries and the low corners stay damp year round. On the Bethpage Road ridge the downhill house on every cross street takes the surface water off the whole block. In each of those cases the house next door, thirty feet uphill, may be a perfect liner candidate while this one needs drainage first. Soil compounds it, because Cecil is dominant here and generally behaves, but Enon with its high shrink-swell and a moderate-shrink-swell series in the same family turn up in the same neighborhoods and Iredell sits on the low ground, so two houses a block apart genuinely do not behave the same way.
East on the granite belt through Faith, Granite Quarry, Rockwell and parts of China Grove the calculation shifts again in a way that is counterintuitive. Shallow bedrock under thin soil means less soil column to move water upward, so in some spots the ground emission a liner would be intercepting is genuinely lower than it would be on deep clay. But water that cannot drain downward perches on the rock and travels sideways, so it arrives at a crawl from an unexpected direction and it arrives as liquid rather than vapor. That is the wrong problem for a ground retarder, and out there the correct sequence is nearly always surface grading and exterior water management first, with the liner as the finishing step once the ground under the house has been given a reason to stay dry.
On permits, a straight ground vapor retarder in an existing vented crawlspace is generally not the kind of alteration that triggers a building permit, since nothing structural, electrical or mechanical is changing and the ventilation is staying as it is. I still confirm it for the parcel rather than assuming, because the moment a scope adds equipment, changes the ventilation, or touches structure, it is a permitted job and the desk depends on where the house sits. City limits is the deciding line, not the county line. Inside Kannapolis, including the Rowan-side neighborhoods of North Kannapolis, Jackson Park and the Kannapolis Lake blocks, that desk is Cabarrus County Construction Standards at 65 Church St S Suite 280, 704-920-2128. Outside the city on the Rowan side inside the extraterritorial area, City of Kannapolis Planning at 401 Laureate Way, 704-920-4350 clears the zoning first and Rowan County Building Inspections at 402 N Main St Room 207 in Salisbury, 704-216-8619 handles the rest. Beyond that line it is whichever county the parcel falls in, which for Enochville, Landis, China Grove, Faith, Rockwell and Granite Quarry is Rowan and for Mount Pleasant and the Lake Fisher side is Cabarrus.
One last local note that saves confusion on paperwork and deliveries. Kannapolis covers eight postal zips and six of them were historically designated to other city names before all in-city properties were recognized as Kannapolis addresses, so residents here routinely write an old city name on their mail and it is entirely normal. 28082 is a post office box zip rather than a delivery area, which occasionally catches out a material drop. For anything that has to be filed or scheduled, I work from the parcel identification number rather than the mailing address, and I recommend you ask any contractor to do the same.
Timing matters more on this scope than owners expect, in both directions, and it is worth planning around. What a crawl looks like in the second week of February and what it looks like in the third week of August are so different that an assessment done in one season has to be read with the other in mind, which is why I lean on physical evidence of past water rather than on whether the ground is damp under my hand today. The wettest stretch of the year here runs through late winter and early spring, and a crawl inspected then is showing you close to its worst case, which is useful. A crawl inspected in a dry September is showing you its best, and that is when people get talked into scopes that turn out to be wrong in March. As for doing the work, the installation itself is indifferent to weather since it happens under a roof, and the four inches of snow this city averages in a year has never cost anybody a scheduled day. The one real constraint is that the exterior half of the scope, the grading and downspout work that makes the liner hold, wants unfrozen ground and a week without heavy rain, so on a winter job those two pieces sometimes land on different days.
Cartown (28083, 28081) on the car-make grid is the cleanest liner work in the city. Chevrolet Street, Buick Avenue, Cadillac Street, Ford Street, Plymouth Street, Packard Avenue, Desoto Avenue, Dodge Street, Chrysler Street and Lincoln Street, with South East Avenue and South Harding Avenue on the edges and Dale Earnhardt Boulevard nearby. Compact post-war houses on continuous block perimeter with eight-by-sixteen vents and low clearance, which means the ground is simple, rectangular and largely free of columns, and the sheet goes in with few interruptions. The condition that decides candidacy here is not the crawl, it is the alley: these blocks sit low relative to the street and surface water off the alleys can end up under the footprint on the worst lots. On a house where that is happening, grading comes before poly. On the many where it is not, this is a straightforward day.
Royal Oaks (28081, 28083) is where I most often replace builder six-mil rather than install a first liner. The state-name grid along Alabama, California, Dakota, Kansas, Michigan, Tennessee, Texas and Virginia Streets, plus Royal Oaks School Drive, Suburban Avenue and Coliseum Avenue, is 1950s through 1980s tract on block perimeter with standard vents, and the poly the builder laid is decades past useful. The other thing I find in nearly every one of these crawls is original fiberglass that has fallen out of most of the bays and is lying on that poly, and it all comes out. What makes these lots easy is also what makes them deceptive: they are flat with shallow grade, so groundwater is rarely the issue, but roof water discharged at the foundation for thirty years absolutely is, and the gutter work is not an afterthought on this street.
North Kannapolis (28081, 28083, 28088) is the most efficient liner work anywhere on my map because the housing repeats. Out the numbered grid along East 17th, East 22nd, East 27th and East 31st Streets, back across West 18th and West 21st, and through Blackwelder, Summit, Springdale, Rosemont and Brookside Avenues, the blocks are lines of near-identical one-story frame houses on brick piers with shallow clearance. Once I have done one of them I know the exposed area, the column count and the debris volume for the rest of the block within a narrow margin, which means I can tell an owner on East 27th Street what to expect before I have opened the hatch and then go verify it. These are Rowan County parcels inside Kannapolis city limits, which matters for anything permitted, though a straight ground retarder generally is not.
West Brook and Village Park (28081) along West A and West C Street, West 7th, 8th and 9th, and Vance, Oak, Church, Franklin, Cedar, Glenn and Wayne Avenues is village stock with two complications that bear directly on this scope. The rear shed rooms and enclosed back porches each sit on their own separate piers, and frequently over their own separate compartment of crawl with restricted access from the main space, so the exposed area is larger than a rectangle drawn on the plot plan and the material has to reach it. And several blocks step down toward the Irish Buffalo Creek headwaters, so the low side of a footprint can be wet enough that this is a drainage job with a liner at the end rather than a liner job. The mature street trees that pack every vent with leaf litter each autumn are the other item, and clearing and rescreening those openings is part of the work here rather than an extra.
Centerview (28081, 28083) is two housing types on one street and therefore two versions of this job. Along Centerview Street, Center Street, North and South Rose Avenue, North East Avenue, Basin Avenue, Celia, Fairview, Hillside, Pineview and Lakeview Streets, mill-village frame on brick pier sits beside 1950s brick ranch on block, sometimes on adjoining lots. Under the frame house I am working around a field of columns and fitting the sheet to each one. Under the ranch next door it is an open rectangle with a continuous wall to terminate the edge against, and it goes in faster. The western blocks fall toward Cold Water Creek tributaries and the low corners stay damp year round, so on that side of the neighborhood I check for liquid water carefully before quoting sheeting.
Shady Brook and Bethpage (28081) along Shadybrook Drive, Bethpage Road, Oakwood Avenue, Rainbow Drive, Klondale Avenue, Rosewood Avenue, Magnolia Avenue, Cherrywood Street, Beechwood Street, Longview Avenue and Westgreen Drive is a post-war brick ranch belt with tight crawls and good perimeters. The defining local fact is the ridge that Bethpage Road runs along, which sorts every cross street into an uphill side and a downhill side. Uphill houses are usually ideal candidates for exactly this scope and nothing more. Downhill houses on the same street take the surface water off the whole block and need that addressed before anything goes on the ground. The standard find in both cases is foil-faced fiberglass in the joist bays with about half of it already on the dirt, and it comes out and does not go back.
Forest Park (28083, 28081) along Forest Park Drive, Centergrove Road, Eastwood Drive, Ridgeway Drive, Scottish Square Drive, Mitchell Glen Street, Carolina Avenue, Pennsylvania Avenue, South Little Texas Road and Valwood Street presents the tightest installation conditions in the city under the stepped-down section of a split-level. Sheeting is bulky before it is unrolled, and getting it to the far end of a low bay means cutting to size outside and carrying it in as smaller pieces, which means more seams and more lap detail rather than fewer. That is a labor difference and I plan it into the day rather than discovering it. Original vents on this stock are undersized relative to the footprint, so the ventilation half of a wall-vented crawl is already working at a disadvantage here, and cutting the soil contribution is doing proportionally more of the work than it would in a well-vented house.
Wildwood and Glass (28081) along Wildwood Drive, Sherwood Drive, Robinhood Lane, Little John Trail, Nottingham Road, Rogers Lake Road, Westwood Drive, Maplewood Avenue, Briarwood Street, Settlers Ridge Drive and Brookcrest Drive has the heaviest canopy on my map, and for a vented crawl that is a direct problem rather than an aesthetic one. Leaf litter packs the vents every autumn and the north side of the crawl never gets sun or moving air, so it stays the wettest part of the space. In the ground-retarder scope that means the vent service is not a courtesy line item, it is half the reason the job works, and I will tell an owner honestly that if the vents are going to be packed solid every October, the liner alone will underperform. Root heave under piers and porch slabs is common enough here that I look for a lifted column before laying anything over the ground around it.
Downtown Kannapolis (28081, 28083) puts village houses on North and South Ridge Avenue, Oak Avenue, Vance Avenue and East 2nd and 3rd Street next to the Research Campus and ballpark rebuild along Laureate Way, North Research Campus Drive, Cannon Baller Way and Chestnut Avenue. On the old houses this is column-heavy liner work over original 1907 ground. What owners here should know is what does not apply to them: as of March 2026 Kannapolis has no local historic district and no historic preservation commission, so nothing about this work is design-reviewed and there is no approval to obtain. A downtown business petition covering the remaining historic blocks and the mill houses around the circle gathered 651 signatures beginning February 18, 2026 and staff has been studying how other North Carolina cities run theirs, so it is a live question. Even so, a sheet of polyethylene on your dirt is invisible from the sidewalk under any regime.
Jackson Park (28083, 28081) along Jackson Park Road, Jackson Street, East 10th, 12th and 13th Streets, Sides Avenue, Graham, Ingram and Craven Avenues and Woodlawn Street mixes older frame on brick pier with a heavy layer of 1960s and 70s block-perimeter ranches. The line I draw here is geographic and it is sharp: the East 10th through 13th blocks fall toward the Irish Buffalo drainage and hold water at the low end of the crawl after any sustained rain, and those houses need the water dealt with rather than covered. Elsewhere in the neighborhood this scope is often exactly right. The other local feature is long owner tenure and multiple generations of do-it-yourself repairs, which for a liner job means an unusually cluttered crawl and a real debris removal component before any sheeting comes off the roll.
Kannapolis Lake and Nob Hill (28081) along Pendleton Drive, Lakewood Drive, Nob Hill Drive, Rainbow Drive, Pump Station Road, Westlake Drive, Lake Hill Drive, West 8th Street, Hilltop Avenue, Rollingwood Drive and Woodcrest Drive is the area where I am most cautious about promising what a ground retarder will deliver. Heavy summer fog off the lake pushes crawl humidity up faster here than anywhere else in the city, and in a vented crawl that incoming air is the part the liner cannot touch. On the upslope lots the scope works well. On the downslope side the houses sit in a high water table with block perimeter foundations that weep at the cove joint, which is liquid water and a different conversation. Any regrading here is constrained by the WS-III protected water-supply watershed and gets confirmed with the city before a shovel moves.
Lake Fisher (28083) and Kellswater Bridge (28081) sit at opposite ends of this scope. Out along Lake Fisher Road, Brantley Road, Moose Road, Turkey Road, Sides Road, Camp Julia Road, Fisher Ridge Road and Brantley Creek Drive, the ground is the wettest I work and a liner by itself is rarely the honest answer, so I quote drainage or I decline. Over on Kellswater Bridge Boulevard, Donegal Drive, County Down Avenue, Coleraine Avenue, Dungannon Way, Keady Mill Loop and Trostan Turn, the houses are 2000s and 2010s with thirty to forty-two inch crawls and builder six-mil already down, and the question is usually whether the owner wants that sheeting replaced in kind or wants to move to a closed assembly. Replacing in kind is a legitimate choice and I will do it without argument. This is also the only area on my map with an active HOA and architectural review, so any exterior item attached to the scope gets checked against the covenants.
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Outside Kannapolis I work the Rowan mill towns to the north, the rural pocket to the west, and the older country east through both counties. The scope itself is portable, because a ground vapor retarder is the same physics anywhere. What changes town to town is whether the crawl in front of me qualifies for the smaller scope at all, and out here that answer is no more often than it is inside the city, mostly because of what the foundations are and where the water goes.
Landis (28088) is a mill town with the same lineage as the Kannapolis grid, one-story frame on brick pier with shallow crawls and rear shed additions, along North and South Main Street, South Central Avenue, Linn Avenue, East and West Ryder Avenue, South Beaver Street, North Chapel Street, East and West Mill Street, Cold Water Street, South Zion Street and West 3rd Street. The repetition works in an owner's favor here the same way it does on the North Kannapolis blocks. What sorts the town for this scope is Cold Water Creek, which runs through the middle of it. The blocks nearest the creek have the shortest clearance and the highest standing water of any mill-town stock I work, and on those a liner is the last step of a longer job rather than the whole job. A few streets away from the water the same house type is a clean candidate. Landis is Rowan County for anything permitted, unlike the Kannapolis blocks just south of the town line.
China Grove (28023) along North and South Main Street, North and South Franklin Street, East and West Centerview Street, East Church Street, North Myrtle Avenue, Swink Street, Patterson Street, Salisbury Street, Chinaberry Drive and Millstream Drive has a pre-1930 core on brick pier and rough fieldstone, and several of those houses have no continuous perimeter at all. That does not disqualify a ground retarder the way it disqualifies a sealed assembly, which is a distinction worth making, because the liner only has to cover ground and does not need a wall to terminate against. What it does mean is more edge detail, more ballast, and an honest conversation that the crawl will remain very open to the outdoors regardless of what is on the dirt. Cold Water Creek rises just northeast of town, so the north-side blocks sit near the headwater seeps and I check those carefully for liquid water first.
Enochville (28081, 28023) along Enochville Road, Enochville School Road, North Enochville Avenue, Overcash and Upper Overcash Avenue, Linn Avenue, Dark Hollow Road, Cannon Farm Road, Knight Farm Road, Woodsdale Drive, Springbrook Drive and Pleasant Hill Drive is rural west Rowan with older farm and mill-worker houses on rough fieldstone and brick pier plus later ranches on block. The ranches are ordinary liner work. The older houses take longer because irregular stone columns do not take a clean cut-and-fit detail, so the sheet gets dressed up onto them and ballasted instead. Two administrative notes that matter more than they sound. Almost everything is on septic, which is only relevant to this scope if the work expands to include drainage, and the Kannapolis extraterritorial line runs through the area, so the permit path differs parcel to parcel if the job ever becomes a permitted one.
Mount Pleasant (28124) is 1850s to 1930s academy-town housing on cut stone and brick pier, an entirely different lineage from the mill village, along North and South Main Street, East and West Franklin Street, Barringer Drive, North and South College, Crowell Street, Ludwig Street, Mount Pleasant Road South and West and Historic Hill Drive. The characteristic feature for this work is the rear ells added across generations, each with its own foundation and frequently its own separate crawl compartment behind a masonry wall with no opening. What looks like one crawlspace on a plot plan is often three, and quoting exposed ground area from the outside dimensions of the house will be wrong by a wide margin. I measure each compartment and I note in the scope how material gets into the ones with restricted access. Rural parcels are on septic and well, and Cabarrus County Construction Standards handles anything permitted.
Faith (28041) along North Main Street, South Main Faith Street, Quarry Street, Balfour Quarry Road, Faith Road, East and West 2nd Street, Church Street, Fisher Faith Street, Stoney Heights Drive, Woodbury Drive and Log Barn Road sits on the Salisbury Pink granite belt, and the ground preparation is the entire difficulty of a liner job here. Rock close to grade cannot be removed, so instead of clearing a surface I am padding and dressing around stone that will not move, and the sheet has to be cut to fit rather than rolled out. Pre-war houses on locally cut fieldstone piers add the same edge-detail work I see in Enochville. The compensation is that a thin soil column over rock emits less vapor than deep clay does, so where the surface water has been managed, these crawls can perform well with nothing more than a properly fitted retarder.
Rockwell (28138) along North and South Hambley Street, Depot Street, Main Street, Lower Stone Church Road, Salisbury Street, China Grove Highway, Gold Hill Avenue, Railroad Avenue, Trexler Avenue, Klutz Street and Huntington Ridge Drive has a pre-1940 core on brick pier and stone with outlying 1960s to 2000s block-perimeter ranches. The ranches are routine. The item I flag out here every time is converted farm outbuildings, which are common and which frequently have no defined crawlspace at all under the converted portion, just a partially enclosed void with irregular ground and no consistent clearance. Covering that ground is still worth doing and it is still the same physics, but it is not a standard liner job and I scope it as its own thing. The 28138 zip also crosses into a sliver of Cabarrus, so I confirm the county rather than reading it off an envelope.
Granite Quarry (28072) along North Main Street, South Main Gq Street, Dunns Mountain Road, Old Stone House Road, East and West Bank Street, East Church Street, North Oak Street, Balfour Quarry Road, Kluttz Street, Meadow Wood Drive and Stonewyck Drive sits on shallow bedrock near the Balfour Pink quarries and the Old Stone House that has stood since 1766, with stone piers cut on site under the oldest houses. Perched water is the pattern here, arriving laterally because it has nowhere to go down to, and it shows up at a low corner from a direction that makes no sense until you know what is eight inches under the yard. For this scope that means the outside work carries the job: grading and surface management determine whether a ground retarder is the finishing touch or a sheet of plastic with water running under it. Salisbury is where the Rowan County desk sits, at 402 N Main St Room 207, which is only relevant here if a scope grows past a straight liner into permitted work.
There are towns I do not present as service areas, and I would rather say so than pad a list: Concord, Mooresville, Huntersville, Mint Hill, Weddington, Statesville, Davidson and the metro to the southwest are covered elsewhere. It matters on this page specifically because the judgment involved in a ground vapor retarder is almost entirely local. Whether the smaller scope is honest for your house depends on your soil series, which way your block falls, whether rock or clay is under you, how your vents have been treated, and whether the ground has ever had liquid water on it. Those are parcel-level questions in a city where two houses on the same street can have different answers, and nobody gets them right by working from a map of the region.
The visit is free and for this scope it is shorter than a closed-crawl assessment, but it is not a glance through a vent. I go under the whole footprint, because the corners are where the answer is and the hatch is where the optimism is.
The first question is whether this scope is the right one at all, and I settle it with evidence of water rather than with the state of the ground on the day I happen to visit. Silt lines at the base of the piers and walls, staining, where loose debris has floated to and settled, rust on the bottom of any metal sitting on the dirt, and the pattern of any efflorescence on the masonry all tell you whether liquid water has been through there and how high it got. If the answer is yes, a liner is not the job and I will say so at the house rather than in an email a week later.
Then the measurements the scope is actually built from. Exposed earth area taken off the real footprint rather than the heated square footage on the tax card, since porches, additions and separate compartments change it substantially. Pier and column count, because every one is a detail and fourteen of them is a different day than four. Clearance at four corners and at the tightest point, since low clearance changes how the sheet has to be cut and carried in. An obstruction inventory: ductwork, plumbing, abandoned pipe, dropped posts, anything that has to be worked around. Hatch dimensions, because material and debris both have to fit through it. And a debris assessment, since on a village house the removal can be a larger part of the day than the installation.
After that come the readings and the outside walk. A pinless moisture meter down the sill, the girders and the joist ends, and a hygrometer reading logged with the outdoor temperature and dew point beside it so the number means something. Then a count and condition check of every vent opening and vent well, gutters and where the downspouts genuinely discharge, grade at each elevation, and hardscape pitching back toward the house. What you get is a written scope naming the sheet thickness and product, the preparation included, how the laps and the piers are being detailed, what happens with the vents, the outside items, a plain statement of what this scope will not do for you, and a fixed number that does not move after you sign it.
When the visit says this is not the right scope, you still get a scope, and that is deliberate. What I write in that case is the liner proposal you called about plus a numbered list of what has to happen before it, in the order it has to happen, with the reason attached to each item. Sometimes that list is one line about a downspout and the whole thing can be handled the same week. Sometimes it is exterior drainage and a regrade and the liner comes months later. Either way you are holding a plan rather than a refusal, you can put the pieces out to whoever you like, and you can do them a piece at a time as money allows. What I will not do is take the job as asked, install a sheet over ground that is delivering liquid water, and let you find out in April.
There are a few things I ask you for while I am there, and they change the answer often enough to be worth listing. How long you have owned the house, because everything I find under a Kannapolis house was done by somebody and the timeline usually explains it. Whether anyone has ever been under there with a scope of work, and if there is paperwork, all the better. Whether anything is stored on the ground down there, since it comes out and some of it people want kept. Whether a floor has ever felt damp or a room has ever smelled different after rain, and if so which room, because that points me at a quadrant before I ever go under. Whether there is a pet that will find an open hatch interesting. And where the water shutoff is, which I ask on every job for reasons that have nothing to do with vapor. Ten minutes of that at the kitchen table saves an hour underneath and it is the part of the visit that most often changes what I recommend.
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If your crawlspace floods every hard rain, a vapor barrier alone won't save you.
Mold on the joists isn't a cosmetic problem — it's a moisture problem.
If your floors sag, bounce, or slope, the fix isn't a new floor — it's what's holding it up.
It is a piece of plastic on dirt, which is not the same thing. A vapor barrier under the 2018 NC Residential Code R408.2 is a minimum 6-mil polyethylene ground vapor retarder covering exposed earth with joints lapped at least 12 inches, and what the previous owner laid down in the village stock after the 1982 Murdock sell-off is almost never that. The scrap you have is usually 4-mil, unlapped, stopping well short of the walls and the piers, and doubled over in places where it is trapping water against the ground rather than blocking it. It has to come out and a proper retarder goes in over prepared subgrade.
For a vented crawl under R408.2 the code minimum is 6-mil polyethylene and that is genuinely enough for a vapor retarder role. The 20-mil reinforced woven liner is what you install for a closed crawl under R409, because it is also the floor of a serviced space and it has to survive being crawled on by plumbers, HVAC techs, and pest inspectors for the next twenty-five years. On a Kannapolis mill house that is staying vented, 6-mil properly lapped, sealed at the piers, and terminated at the wall is the correct spec, and there is no reason to spend on 20-mil unless you are moving to a closed assembly later.
A vapor retarder blocks vapor coming up out of the soil, not liquid water arriving from outside. On the Lake Fisher, Brantley Road, and Moose Road side, water arrives from outside because the lots sit on lower landforms in the reservoir drainage, so laying a 6-mil sheet over wet ground puts the sheet on top of a pond and nothing changes. The right sequence is bulk water resolution first, meaning grading, gutter and downspout work, and often a perimeter drain and basin, and the retarder goes down last over prepared subgrade. On a wet lot the retarder alone is a cosmetic step.
The physical labor is possible for a fit homeowner at 14 to 20 inches of clearance in the Cartown grid, and I have seen owner-installed barriers that were done well. What people underestimate is subgrade preparation, which is the part that determines whether the barrier lasts. Sharp brick fragments and old coal clinker from the original construction have to be removed or covered, plumbing stubs dealt with, and the perimeter and piers detailed properly with mechanical termination and pier wraps. A 6-mil sheet loose-laid over unprepared ground is the same failure mode as what is already down there. If you do the prep, the sheeting itself is straightforward.
Because a vapor retarder is one part of the moisture control system, not the whole thing. On the 2000s and 2010s builds off Kannapolis Parkway, the builder 6-mil was almost always terminated with adhesive on dusty block, punctured over a decade of trades under the house, and installed without any active dehumidification behind it. In a vented crawl the retarder blocks soil vapor and the vents were supposed to carry off the rest, but the vents deliver more moisture than they remove from May through September in this climate. Either the vents come off and a closed assembly with a dehumidifier replaces it, or the vented crawl gets grading and gutter work outside to reduce the load.
Not the retarder itself, but any discharge routing associated with it does. Enochville along Enochville Road and Overcash Avenue is on septic, and if the vapor work is part of a scope that includes a sump or a condensate discharge, that discharge has to be routed well clear of the drainfield, with a real margin, on a route that has been walked rather than drawn on a plot plan. Kannapolis extraterritorial parcels also need Kannapolis Planning zoning at 401 Laureate Way first, then Rowan County in Salisbury issues the permit through EnerGov.
Piers get wrapped rather than cut around, every single one. A retarder that stops six inches short of a masonry column leaves an exposed ring of soil at every pier, and in a village house on the numbered grid with fourteen or more piers, that adds up to real exposed area in the hardest-to-reach places. The wrap runs up the column, gets mechanically banded or taped, and gets sealed at the top edge with SikaFlex-1a. On the Plant No. 7 typology bungalows with tapered posts on brick bases, the wrap detail is the same but the geometry takes longer to fit.
Leave the gap. The 2018 NC Residential Code and every pest carrier require a continuous inspection band of at least three inches of exposed masonry between the top of the vapor retarder or wall insulation and the sill. That band exists so a termite inspector can read the wall for shelter tubes on the annual visit. Any contractor who runs a barrier all the way up covers that band and creates a fight with your pest company at your next inspection. The band gets left, the retarder terminates on a mechanical fastener with a sealant bead, and the wall stays legible above it.
In most cases no, because a code-minimum ground vapor retarder in a vented crawl under R408.2 is a maintenance item rather than a structural or envelope alteration. The trigger for a permit is when the work becomes an assembly rather than a sheet, meaning the vents come off, the perimeter gets sealed, wall insulation goes in, or a dehumidifier is added, at which point it is a closed crawl under R409 and Cabarrus County Construction Standards permits it at 704-920-2128 through ACCELA. On the extraterritorial Rowan side, Rowan County permits at 704-216-8619 through EnerGov.
The 6-mil sheet itself has a service life that stretches to the point where something mechanical breaks it, and in a well-prepared crawl with no trades traffic that can be a couple of decades. What actually shortens the life is punctures from other work under the house, tears at pier wraps that were not mechanically banded, and slippage at the wall termination when the adhesive lets go. Walk the crawl once a year with a light and patch what you find rather than leaving it, because a tear that stays untended migrates. The 20-mil reinforced woven liner on a closed crawl lasts materially longer for the same reason it costs more.
Yes, and it is worth explaining why the wrap matters rather than leaving a ring of exposed soil at every column. On a Cannon-era village house you often have 12 to 20 brick pier stacks, and a liner that stops six inches short of each one leaves 12 to 20 rings of open dirt at exactly the points that are hardest to reach later for any repair, and any inspection. The wrap runs up the column, gets mechanically banded or taped, and gets sealed with SikaFlex-1a at the top edge. On the village stock this is more than half of the total termination work in the crawl, because there are that many piers to wrap. It is also the part that most builder packages and most cheap retrofit installs skip, which is why a builder liner in this city almost always looks torn or floating around the piers within a decade of installation.
Almost never, and I try to be honest with the owner about why rather than sell a patch as a real fix. Six-mil builder poly from the early 2000s has been in the ground for over 20 years, has been walked on by every trade that has been under there in that time, and has been folded, dragged and cut so many times that patching it is patching a piece of paper that already has more tape than paper. The other honest problem is that the original wall termination on that generation of builder work was adhesive on dusty block, which failed after a handful of summers, so the top of the assembly is unusable regardless of the condition of the ground sheet. What I will do on those houses along the Kannapolis Parkway side and in Kellswater Bridge is strip the existing liner, evaluate the ground and the piers underneath, and install a new 20-mil reinforced assembly with mechanical termination that will actually last.
The code minimum for a vented crawlspace ground retarder under R408.2 is 6-mil, so anything above that is above code, and there is a real argument for 10 or 12-mil in a vented crawl where the liner is not going to be walked on much. What I spec 20-mil for on almost every Kannapolis job is not the vapor permeance, because at that thickness they are all functionally equivalent, but the mechanical durability. In a closed crawl the liner is the floor of a serviced space that gets walked on by me, by a plumber, by an HVAC tech and by a pest inspector for the next 20 to 25 years. A reinforced scrim survives that traffic and a plain sheet does not, and a tear in a closed-crawl liner is a breach in the air barrier as well as the vapor barrier. In a vented crawl on a well-drained Cecil lot where the assembly is a ground retarder only, 10 or 12-mil is defensible; on a wet Iredell lot out toward Lake Fisher, I still spec 20 for durability.
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