Liners, Encapsulation and Dehumidifiers Under a Horry County House

Sheet on the dirt, or a sealed enclosure

Both jobs get called the same thing on the phone, and they are not the same job. The cheap version is loose polyethylene laid over the soil, overlapped at the joints, ending wherever the roll ran out. It does cut evaporation from bare ground, which is real, and on a dry sandy lot with good drainage it can be enough to move a reading. It also lifts at every edge, gets walked out of place by the next tradesman under there, and leaves the piers, the curtain wall and the perimeter open, so the moisture simply comes in around it.

The full version treats the crawl space as part of the building rather than as outdoor space with a floor over it. Heavier liner, joints lapped generously and taped, the sheet mechanically fastened and sealed where it turns up the piers and the inside face of the curtain wall, the sump or drain detailed rather than cut around, and the vents closed. Then a dehumidifier holding a set humidity, draining to somewhere that is not the crawl space, because a bucket nobody empties is just a puddle with a lid. Ask which of the two you are being quoted, in those words, because the price gap between them is large and both get described as a vapor barrier.

Crawl height under Conway houses varies by lot age more than by neighborhood, and the pros we connect you with size a sheet or a sealed liner around that clearance rather than a standard number. A tight foundation near Carolina Forest Boulevard takes less material than an older pier-and-beam closer to town, while lots feeding runoff toward the Intracoastal Waterway or the flatter ground out past Finklea often need the dehumidifier regardless of which barrier gets installed. Get the crawl height measured before either quote firms up.

• Liner thickness stated on the quote, not described as heavy duty
• Seams lapped and taped, not just overlapped and left
• Liner turned up the piers and the curtain wall and fastened, with the top edge sealed
• Vent openings closed properly, framed and sealed rather than stuffed
• Dehumidifier sized for the footprint, with a gravity drain or a condensate pump to daylight
• A humidity gauge left behind so you can read the result yourself

Why the edges are the whole job here

Houses around Conway, Aynor and Loris sit on piers with a block or brick curtain wall closing the perimeter. That means a liner has to negotiate a lot of vertical surfaces: every pier, the inside face of the wall all the way round, the access hatch, the plumbing penetrations. Each one is an edge, and an edge that is not sealed is where humid outside air walks in and where soil moisture bypasses the sheet entirely. The flat middle of the crawl space is the easy part and it is the part everybody photographs.

Sandy fill makes it worse rather than better. Water moves through it quickly after the sort of rain the Grand Strand gets in an afternoon, so the soil under a house near a tidal creek or off the Waccamaw floodplain can be damp again within hours of looking dry. A liner that lifts at the wall gives that moisture a straight route into the air under your floor joists, and the floor above is the coolest surface in reach. That is the condensation people find on ductwork and mistake for a leak.

Conway sits on the kind of high-water-table ground that makes crawl space moisture a structural fact of life, not a bad-luck event, and that holds true whether the house is near downtown or out toward Aynor along US-501 and the surrounding farmland. The licensed pros we connect you with size liners and dehumidifier capacity to that reality rather than a generic square-footage chart, because a system built for drier soil near Loris fails quietly under a house sitting on Horry County's wetter clay.

Closing the vents is not a shortcut, it is the point

Vented crawl spaces were built on the idea that outside air dries out the space beneath a house. That works in a dry climate. It does not work here in July, when the outside air arrives carrying more moisture than the surfaces under your house can hold at their temperature, and promptly gives some of it up on the cold water line and the duct trunk. Opening more vents in a coastal summer imports the problem faster.

So a proper encapsulation closes them, and once they are closed the space needs a way to control its own air. That is what the dehumidifier is for, and it is why a quote with a liner but no humidity control is half a system. Sealing a crawl space also touches combustion appliances and, in some builds, the way the space is conditioned, so this is a job to have specified by somebody who will put the approach in writing and who knows what the local building official expects. Ask whether the design meets current code for a closed crawl space in your jurisdiction, and ask them to say how, not just that it does.

• Do not seal a crawl space with an unvented combustion appliance in it without having that checked first
• Do not stuff insulation or foam board into vent openings and call them closed
• Do not run the dehumidifier drain into a hole in the soil under the liner
• Do not lay liner over standing water and expect it to solve anything

What it does for the pest problem

This is a pest site, so here is the honest link. A liner does not kill anything. What it changes is the reason things want to be there. Damp wood is what powderpost beetles and decay fungi need, and both of those show up on a CL-100 report at the worst possible moment in a sale. Camel crickets, roaches and spiders live in the crawl space because it is humid and dark, and they come up through the same penetrations that were never sealed. Roof rats and squirrels use it as a route rather than a home, but a clean sealed space makes their runs obvious instead of hiding them under loose plastic.

It also makes an inspection worth something. A technician can actually see the sill, the band joist and the piers when there is a light liner underfoot instead of ankle deep debris, so mud tubes get found in the year they appear rather than after the damage. That is the argument for doing this before you need it, not the moisture reading.

Getting a comparable quote

Three companies will quote three different jobs unless you pin the scope down. Ask each for the liner thickness in mils, whether seams are taped, whether the liner is fastened and sealed at the piers and curtain wall, whether vents are being closed, and what dehumidifier is included and where it drains. Ask what happens to any debris, old fallen insulation and standing water first, because none of that is optional and all of it can appear later as an extra.

Then ask what is warranted and for how long, in writing, and whether the warranty covers the liner staying sealed or only that it was installed. Guide figures for this kind of work sit on the pricing guide, and they are wide on purpose: a small slab-adjacent crawl in Carolina Forest and a large pier built house in town with poor access are not the same afternoon.