How much does it cost to encapsulate the crawl space for a 3,000 sq ft house? Is it worth it?

For a house that size in New Hampshire, crawl space encapsulation usually runs $3,000 to $25,000. The price tracks the square footage under the house, the shape of the crawl, and how much prep the space needs first. For most homes with a damp, musty crawl, yes, it is worth it. You get a dry space, cleaner air upstairs, and a foundation that stops feeding moisture into the house.

That is the short version. Here is what is going on down there.

Why the crawl gets wet in the first place

Most crawl spaces sit on disturbed backfill. That is the looser soil the builder put back when the foundation went in. It drains slowly and holds water. So after a hard rain or a spring thaw, water collects right at the foundation and works its way in. NH frost heave makes it worse by pushing on the walls through the winter.

Then the dirt floor does its part. Bare soil gives off moisture all day. That moisture rises into the joists, the subfloor, and eventually the rooms above. You smell it before you see it. Musty air, a cold floor, sometimes mold on the framing.

What encapsulation actually is

Encapsulation seals the crawl off from the ground and the outside air. Here is what we install:

• A 12-mil wall vapor barrier up the foundation walls.
• A 20-mil floor vapor barrier across the dirt.
• Dimpled drainage matting under the floor barrier so any water has a path.
• Spray foam to seal the seams.
• A dehumidifier to hold the space dry.
• A sump to handle water if the crawl takes any.

Put together, the crawl turns into a sealed, dry room. The barrier is rated tough enough to crawl on and move around in. This is different from our Forever Dry System, which is a basement job. Crawl spaces get encapsulation.

What drives the cost

The biggest factor is the footprint. A 3,000 sq ft house has a bigger area to cover than a small ranch, so it sits at the higher end of $3,000 to $25,000. After that:

• Headroom. A tight crawl is slower to work in.
• Standing water or a wet floor. That may need the sump and matting doing more lifting.
• Old debris, junk, or a torn-up vapor barrier from a past job we have to pull out first.
• Whether you want radon handled at the same time.

We give you the number after we see it. The free inspection is how we know which of these apply to your house, and we get the written quote back to you within 24 hours.

Is it worth it?

For a lot of homes, the moisture is the whole problem. Seal the crawl and the musty smell upstairs goes away, the floors feel warmer, and the framing stops rotting on a slow clock. The Department of Energy notes that up to about a third of a home’s heat loss can come through an uninsulated foundation or crawl, so a sealed crawl can take some load off your heating in a NH winter.

Now the part where we teach instead of sell. If your crawl is already dry, with a sound vapor barrier and no smell, you may not need this yet. We will tell you that to your face. Encapsulation earns its keep when there is real moisture, an odor, or framing starting to suffer. If you have a dirt or fieldstone crawl with a radon reading, ask us about a sub-membrane radon system while we are down there. It pairs well with the same barrier work.

Crawl encapsulation carries a 25-year warranty on our work, and the wall vapor barrier is backed 25 years too. The sump system is covered 3 years, and the dehumidifier 5 years.

Talk to us

Call us at 603-610-1770 or book your free inspection. We will crawl the space, tell you what it needs and what it does not, and send a written quote within 24 hours.

Want more on the parts of the job? See crawl space services, radon mitigation, and the 603 guarantee. If your problem is really a basement, start with basement waterproofing instead.

Related questions

Does encapsulation include a dehumidifier? Yes. A dehumidifier is part of the system. It holds the sealed crawl dry year round so moisture does not creep back in. It carries a 5-year warranty.

Will encapsulation fix a radon problem? Not by itself. Sealing helps, but a high radon reading needs an active system. For a dirt or fieldstone crawl we install a sub-membrane depressurization system. Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250, and a test is $50, credited toward the job if you move ahead. EPA says to fix at 4.0 pCi/L and to consider fixing between 2 and 4.

Do I need encapsulation or basement waterproofing? Depends on the space. A crawl space gets encapsulation. A full basement gets our Forever Dry System, which is full-perimeter interior drainage, a sump, a wall vapor barrier, and a dehumidifier. We will tell you which one your home actually needs at the inspection.

Is exterior digging a better fix? In our field experience, no. Exterior excavation jobs tend to fail in a couple of years and cost more to do. The durable fix for water is interior drainage and a sealed crawl.