Crawl space encapsulation in Lexington

Crawl space encapsulation seals the space under your house off from humid outdoor air and from the ground. For Lexington homeowners with a musty smell, damp insulation or condensation on ducts, it's the most complete fix: the vents get closed, a heavy liner goes over the soil and up the foundation walls, and a dehumidifier or a small supply of conditioned air keeps the humidity down.

What is encapsulation, exactly?

The building code calls it an unvented crawl space. Instead of trying to dry the space with outside air, you keep outside air out and treat the crawl space as part of the house. The three parts are a sealed ground and wall liner, sealed vents and openings, and some form of air control. Leave out the last part and the space can trap moisture rather than shed it.

Signs encapsulation might be the right fix

• The house smells musty, especially in midsummer
• Ducts or pipes sweat under the floor
• Floor batts are wet, sagging or falling down
• Old plastic over the dirt is torn or only partly covers it
• You've had mold or wood decay treated before and it came back

Why it comes up so often in Lexington

Lexington averages close to 50 inches of precipitation a year and has long, humid summers. Older houses in neighborhoods like Chevy Chase, which grew up in the 1920s as an early automobile suburb, often sit on block or stone foundations with vents and a bare dirt floor. The limestone-derived soils under much of the county hold moisture, and some lots drain toward low spots. That combination is exactly what an encapsulation is designed to handle.

How does a typical job go?

1. Inspection. Checking for water entry, rot, insect damage, plumbing leaks and the condition of the insulation and ducts.
2. Water control. Gutters, downspout extensions, grading, or an interior drain and sump if water gets in.
3. Cleanup. Pulling out old plastic, wet batts and debris.
4. Sealing. Closing vents and gaps around pipes, wires and the access door.
5. Liner. Laying a heavy ground cover with lapped, taped seams and fastening it up the walls and around piers.
6. Air control. Usually a dehumidifier, sometimes a supply-air duct from the HVAC system.

What does Kentucky's code ask for?

Kentucky's residential code is based on the 2015 International Residential Code. Its unvented crawl space section asks for a continuous vapor retarder over the exposed earth, with joints lapped and sealed and the edges carried up and sealed to the foundation wall, along with an approved way to handle the air, such as continuous exhaust or a conditioned air supply. Lexington's Division of Building Inspection or your county office can tell you whether your project needs a permit.

What affects the price?

• Square footage and height of the crawl space, and how easy it is to move around in
• Liner thickness and whether walls and piers are fully covered
• How much old insulation and debris has to come out
• Drainage work needed first
• The air control method and any electrical work for it
• Wood repairs found during the inspection

The contractor sets the price after seeing and measuring the space. We don't publish prices, and any number quoted before someone has been under the house is only a guess.

Encapsulation or just a new ground cover?

If the space is dry, the vents work well enough and the only problem is torn plastic, a new vapor barrier may be all you need. If you have humidity problems, sweating ducts or a smell, a full encapsulation usually solves more of the problem for the money.

Towns this covers

• Lexington
• Nicholasville
• Georgetown
• Versailles

Related services

• Vapor barrier replacement
• Crawl space dehumidifiers
• Crawl space insulation
• Floor joist and sill repair

For the Kentucky code, karst and radon background, see the Lexington crawl space guide.