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.
Half the vapor barrier calls I get in Concord are homeowners who were told by another contractor that they need a full encapsulation and want a second opinion. The honest answer on any given inspection is that some houses need the full sealed-crawl system with a dehumidifier and wall termination, and some houses need a proper 20-mil ground cover, sealed vents, and a monitored season before we commit to the bigger scope. Vapor barrier as a standalone product is not encapsulation. It is one component of an encapsulation, and on the right house at the right moisture load it is enough to move the needle from failing to acceptable while you decide about the rest.
Last summer I did exactly that on a 2007 build in Robinson Church between Concord and Harrisburg. 2,100 SF crawl, block perimeter, existing 6-mil builder plastic in mostly-intact condition, foil-faced fiberglass batts still stapled up in about 70 percent of the joist bays. Moisture readings were high — RH averaging 78 percent in June — but the wood was probing solid, there was no active water, and the homeowner had budget for one scope and wanted the biggest improvement per dollar. We tore the 6-mil, put down 20-mil YellowGuard with 12-inch overlaps and wrapped piers, sealed the vents with closed-cell foam blocks and mechanical covers, cleaned out the failing fiberglass, and did not install a dehumidifier. RH dropped from 78 to 63 percent within three weeks. Still not ideal — you want under 60 for long-term wood protection — but a substantial improvement, and the homeowner had baseline data to make the dehumidifier decision the following summer. She called us in August to add the dehumidifier and we ran it back for a Santa Fe Compact 70 install. That is a two-phase approach that some houses justify.
What follows is what actually goes into a Concord vapor barrier job, when I recommend standalone vapor barrier versus full encapsulation, and why the material spec is not negotiable regardless of scope. Free on-site inspection anywhere in Concord, Harrisburg, Kannapolis, and out to Huntersville.
A proper vapor barrier install on a Concord subdivision job — Christenbury, Moss Creek, Cox Mill, Robinson Church — starts with tearing out the existing 6-mil builder plastic. On a 2000s or 2010s house the builder plastic is almost universally in one of three states: torn to shreds after decades of HVAC service and pest control access, intact but degraded and gassing off, or replaced once already with another sheet of 6-mil that has now degraded again. In all three cases it comes out. We haul it out of the crawl in sections through the crawl door, bag it, and dispose of it as construction debris.
Then we clean the dirt floor. This is a step contractors skip and it matters. Any protruding rocks, pier construction debris, HVAC drop-off, or organic material stays where it is and it will telegraph through the 20-mil in about a month, potentially puncturing the liner from below. We rake and level, remove sharp objects, and if there is any standing water we identify the source before we lay anything down. Then the 20-mil YellowGuard, Americover, or Viper CS goes down in the largest sheets that fit through the crawl door, with 12-inch overlaps at every seam. Every pier gets individually wrapped with cut-to-fit pieces sealed to the ground sheet with Polyken 337 double-sided PSA seam tape. Every seam gets top-taped as a redundancy.
On a standalone vapor barrier scope (no full encapsulation), the perimeter treatment is where we make a judgment call. On a Christenbury or Cox Mill block-perimeter crawl we run the liner up the wall 6 to 12 inches and fasten with mechanical clips and a bead of SikaFlex-1a on the wall side, but we do not install the full mechanical termination bar that a proper encapsulation requires. The reason is that without a dehumidifier the wall termination is going to see cyclic humidity anyway, and the mechanical bar without dehumidification does not deliver the benefit that justifies the cost. On a full encapsulation with dehumidifier the mechanical bar is mandatory. On a standalone vapor barrier we can defer it and revisit if the homeowner upgrades to full encapsulation later.
Vents get sealed on any Concord vapor barrier job worth doing. Closed-cell foam blocks inside, mechanically fastened covers outside. Vented crawls in this climate are the whole reason the humidity is bad — leaving vents open with a new vapor barrier is like putting a lid on a boiling pot with a hole in it. Cabarrus County does not require a permit for vapor barrier or vent sealing. Neither is a permitted trade in North Carolina.
Downtown Concord pre-war houses are a completely different conversation. On a 1900s-1930s Union St or Cabarrus Ave house with unmortared brick piers and rubble-fill perimeter, a standalone vapor barrier scope is not really an option. The perimeter walls cannot be properly terminated against without the mechanical bar bedded into intact brick courses, and without full encapsulation and dehumidification the moisture load overwhelms any partial improvement. On downtown houses we recommend the full encapsulation scope from day one and we are honest that vapor-barrier-only is not going to move the needle enough to justify the cost.
Material is 20-mil reinforced polyethylene. Non-negotiable. YellowGuard, Viper CS, or Americover woven poly depending on supplier availability. Never 12-mil, never 10-mil, never the 6-mil builder plastic that comes out of every subdivision crawl we work on. The 20-mil scrim gives seam tape something to grip and it holds up to foot traffic from any HVAC tech or pest control operator who has to work under the house over the next 20 years.
Seams overlap 12 inches minimum. Seam tape is Polyken 337 or Nashua 357 double-sided PSA — butyl-based tape does not survive Cabarrus County summer temperatures under an unconditioned crawl and we stopped using it years ago after seams walked apart on August service calls. Every pier gets individually wrapped with cut pieces sealed with the same seam tape and top-taped for redundancy. Skirted piers (a continuous sheet run around the pier without wrapping each pier individually) fail at year three, every time, because the pier concrete wicks ground moisture up behind the liner and traps it.
Vent seals are closed-cell foam blocks (2-inch thick, cut to fit each vent opening) on the inside and mechanically fastened plastic vent covers on the outside. Crawl door replacement is optional on a standalone vapor barrier scope but recommended — insulated gasketed hatch replaces the flimsy louvered thing that came with the house. If the homeowner defers the door replacement we at least gasket the existing door with EPDM weatherstrip.
Perimeter treatment on standalone vapor barrier: mechanical clips every 24 inches with a continuous bead of SikaFlex-1a on the wall-side seam. Full mechanical termination bar (1-inch by 1/8-inch aluminum stock, 2-1/4-inch masonry screws every 12 inches, SikaFlex-1a bed) is reserved for full encapsulation scope with dehumidifier. Deferring the bar on standalone scope is not a shortcut — it is a legitimate scope choice when the dehumidifier is not part of the current phase.
Yes — Concord is a regular vapor barrier route. Free on-site inspection anywhere in Concord, fixed written quote before we touch anything.
Concord vapor barrier work is often the phase-one entry point for subdivision homeowners in Christenbury, Moss Creek, Cox Mill, or Robinson Church who want the biggest moisture improvement per dollar while deferring the dehumidifier decision. Downtown pre-war houses with rubble-fill perimeters cannot get a proper vapor barrier install without the full encapsulation scope — the perimeter termination requires mechanical bar and dehumidification to work.
28025, 28027. All Cabarrus County addresses covered.
Depends on your current moisture load and your budget. On a house with no active water, wood that is probing solid, and RH readings under 75 percent, a proper 20-mil vapor barrier with sealed vents will drop your humidity 10 to 15 points and often gets you into the 60-to-65 percent range through the summer. That is not ideal — you want under 60 for long-term wood protection — but it is a meaningful improvement. On a house with active water, wood damage, or RH already above 80 percent, a standalone vapor barrier is not going to move the needle enough and you need the full encapsulation with dehumidifier from day one. We are honest about which category your house falls into on the inspection.
Two reasons. First, foot traffic. Every HVAC tech, pest control operator, plumber, and electrician who works under your house over the next 20 years is going to walk on that liner. 6-mil tears the first year. 10-mil tears within 3 to 5. 20-mil reinforced poly with a woven scrim does not tear under work boots. Second, seam tape adhesion. The scrim in 20-mil material gives the seam tape something structural to grip, so the seams stay sealed for the life of the install. Tape on 6-mil peels within a summer because there is nothing under the adhesive but a smooth plastic surface.
Yes and about 20 percent of our subdivision jobs go phase-two exactly that way. We install the 20-mil, seal the vents, monitor the RH for a season, and if the moisture load stays above 60 percent through August the homeowner calls us back for the dehumidifier and any wall termination upgrades. That is a half-day install for the dehumidifier itself plus the Cabarrus electrical permit for the dedicated circuit. If we know upfront the second phase is likely we can leave the perimeter setup easy to convert.
Because the perimeter walls on a 1900s-1930s downtown Concord house are typically dry-laid stone or unmortared brick with rubble-fill between the piers. You cannot terminate a wall liner against that without the mechanical bar bedded into whatever intact brick courses you can find. Without full encapsulation and dehumidification the humidity load overwhelms any partial improvement — moisture just moves through the porous perimeter faster than a ground vapor barrier can compensate for. On downtown pre-war stock we recommend the full scope from day one and we tell you honestly that vapor-barrier-only is not going to justify its cost.
Free on-site Concord inspection. Fixed written quote. Call (980) 227-1769 or book below.