Encapsulation seals a crawl space off from the ground. Liner on the dirt floor, barrier up the walls, the whole thing tied together and sealed, and a way to control the moisture that is already in there. In Andover it usually runs $3,000 to $25,000, quoted in writing after we look at it.
How do you know your crawl space needs it?
You usually smell it before you see it. That damp, closed-up smell in the room above the crawl is air coming up out of the crawl, because that is what air does in a house. It moves up.
Other things we get called for:
- Floors above the crawl that feel cold or springy
- Condensation on ductwork or pipes down there
- Rot at the bottom of framing, or fungus growing on joists
- Mice, red squirrels, anything that found a way in and stayed
- A dirt floor that is damp to the touch even in a dry stretch
An unhealthy crawl space will rot your house from the inside out. It is not the kind of thing that holds steady and waits for you.
What actually goes in
A real encapsulation is not a sheet of plastic thrown on the dirt. Ours is a liner across the full floor, barrier run up the foundation walls, everything lapped and sealed so there is no open seam, and moisture control sized for the space. We spec a heavier liner on the floor than on the walls, because the floor is what gets walked on when somebody has to get down there to run a wire in ten years.
If there is standing water, that gets solved first. Sealing a wet crawl just traps the water on the inside of a nice new liner.
What it costs in Andover
$3,000 to $25,000, and that is a wide range because crawl spaces are wildly different from each other. What moves your number:
- Square footage. The single biggest driver.
- Headroom and access. A crawl you can sit up in is a different job from one somebody has to army-crawl through with materials.
- What is down there now. Old insulation falling out of the joists, debris, a previous half-attempt at a vapor barrier. It all has to come out first.
- Whether there is water to deal with. Drainage or a pump adds to it.
- Rot. If framing is gone, that is structural work and it happens before the liner.
We give you a written number after somebody has been in the crawl. Not before.
The warranty
Crawl space encapsulation carries a 25 year warranty on the liner, the wall barriers and the workmanship. Dehumidification carries 5 years per the manufacturer terms.
One thing worth knowing: if somebody else later fastens into a sealed wall and puts holes through the barrier, that damage is not covered. Tell whoever works down there next that there is a system on those walls.
Questions we get
Should I just add vents instead?
Venting a crawl space in New England means inviting in humid summer air that then condenses on cool surfaces. Sealing is the approach we use.
Do I need a dehumidifier too?
Usually yes for a full encapsulation, because sealing controls where moisture comes from but does not remove what is already in the air. We size it to the space.
Can I do part of it now?
Yes, and people do. Tell us the whole plan so we do the first part in a way that does not have to be undone.
How long does it take?
Most crawls are a day or two once we start. Rot repair or drainage adds time.
What you are seeing, and what it usually means
| What you notice | What it usually points to | What we normally do |
|---|---|---|
| Musty smell in the rooms above | Crawl air moving up into the house | Seal the crawl, then control the moisture left in it |
| Cold or springy floors | Insulation failed, or framing has softened | Check the framing first, insulate after the seal |
| Condensation on ducts and pipes | Humid air meeting cold surfaces | Dehumidification sized to the space |
| Damp dirt floor in a dry spell | Ground moisture coming up continuously | Full floor liner, lapped and sealed to the walls |
| Standing water after rain | Water entering, not just vapour | Drainage or a pump before anything gets sealed |
| Fungus or soft spots on joists | Rot, which is structural | Repair the framing first. Sealing over rot hides it |
How the job runs
Somebody comes out and gets into the crawl. Not a look through the hatch with a torch, actually in there, because you cannot see the far corners from the opening and the far corners are usually where the trouble is.
Then you get a written scope. What is coming out, what is going in, what it costs. If there is rot or standing water, that is its own line and its own sequence, because sealing over either one just hides it under a new liner.
On the day, the old material comes out first. Debris, fallen insulation, whatever the last owner left. The liner goes down across the full floor, runs up the walls, and every seam gets lapped and sealed. Then the moisture control goes in and gets set.
Most crawls are a day or two. Rot repair or drainage adds to that, and we will tell you which one you are before we start rather than after.
What Andover’s own records say about water
Andover keeps unusually good records on this, and they are worth reading before you spend money on a basement.
The town has 29 repetitive-loss structures and 108 active flood policies, and those repetitive-loss properties have drawn $5,382,507 in building payments from FEMA across 81 separate losses (Town of Andover Hazard Mitigation Plan, public review draft, September 2024). Repetitive loss means a property flooded, was paid, and flooded again.
The same plan names the places. Residents and town staff identified Shawsheen Village, the River Street bridge, the Fish Brook area, Dascomb Road, Ballardvale and Clark Brook, North Main Street and the Skug River. Shawsheen Village came up repeatedly as the most flood-prone part of town, with the stormwater problem attributed to an undersized culvert running under the neighbourhood.
And on 8 August 2023 Andover took 8.7 inches of rain in two hours. The Shawsheen at the Balmoral Street gauge went from 24.3 feet at 6:15am to 30.6 feet by 12:45pm, past the 29-foot minor flood stage, with flash flooding near the senior center, the high school and Chestnut Street.
The layer under your basement
This is the part that explains a lot of wet Andover basements, and almost nobody tells homeowners about it.
A densic restrictive layer, which is dense basal-till hardpan, is mapped under 27.1 percent of Andover, at representative depths of 41 to 92 centimetres below the surface (USDA NRCS soil survey, Essex County Northern Part, clipped to the Andover town boundary). By series that runs Ridgebury at 46 to 49 centimetres, Paxton 53 to 71, Woodbridge 66 to 81, Montauk 74 to 92.
Hardpan does not let water through. Water moving down through the soil reaches it and turns sideways instead, and it keeps going until something interrupts it. A foundation wall is exactly that kind of interruption.
The rest of the ground splits close to evenly between thin till at 41.1 percent and coarse glacial stratified deposits at 41.0 percent (USGS Surficial Materials of Massachusetts, SIM 3402). Where NRCS rates drainage, 22.6 percent is poorly or very poorly drained.
All of that is town-scale. It is where we start, not a reading of your lot, and the inspection is free.
What our customers say
603 Basement Solutions put in a perimeter drain system, repaired 2 foundation cracks, and installed a vapor barrier in my basement. What you see in the photos are quick snapshots of a job well done. What you don’t see is a team of professionals that took the time from the first moment they stepped into my house to fully understand my needs and expectations. Everyone from the sales engineer to the office staff to the installation team were kind, professional, and honest. Would highly recommend. Thanks 603 Basement Solutions!
Jon Martell, Google review, 5 stars
That is one of more than 240 Google reviews. We would rather you read them than take our word for anything on this page.
Related pages for Andover
- Basement waterproofing in Andover
- Crawl space services
- Crawl space encapsulation cost
- Every town we cover
- Who you would actually be dealing with
- Basement waterproofing
- Straight answers to basement questions
Book a free inspection in Andover
Somebody comes out, looks at the actual space, and tells you straight what it needs and what it does not. You get a written number for a defined scope. No two hour pitch, because we would rather be at the next house.
If you are looking for a team that isn’t going to treat you like another number, we would be happy to give you an estimate free of charge. We don’t cut corners. We stand behind our work. We care.
Call 603-610-1770 or book your free inspection. We cover Andover and the surrounding towns from our shop in East Kingston, New Hampshire.
Common questions about crawl spaces
- I had my crawl space encapsulated and outside vents sealed. Why have my radon levels gone up?
- I was told of an add-on for my crawl space encapsulation: insulation under the 20 mil white casing. Is that preferred?
- If a house already has a vapor barrier, is there a need for another one?
- If the humidity in your crawl space is 60-70% but in your house it’s lower, do you still need to fix the crawl space?
- Is a little water in a crawl space normal?
- Is a vapor barrier necessary under the subfloor?
- Is there a good ROI on crawlspace encapsulation?
- My home is on a crawl space; the problem is the $20k price tag. Is encapsulating a crawlspace worth the money?
- What are the potential disadvantages of having a crawl space under your house?
- What are the reasons for some houses having basements or crawl
- What are the top reasons for immediate house foundation repair and crawl space encapsulation?
- What challenges should I expect fixing squeaky floors in a house with a short crawl space?
More 603 services in Andover
- Basement Waterproofing in Andover, MA
- Basement Finishing in Andover, MA
- Foundation Crack Repair in Andover, MA
- Radon Mitigation in Andover, MA
