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 Merrimack 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 Merrimack
$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.
Why Merrimack drains the way it does
Merrimack sits on more sand and gravel than most of the towns we cover, and that is measured rather than a feeling.
The town’s own master plan records that stratified drift aquifers underlie approximately 19 square miles, or 57 percent of the Town. Of the SSURGO-mapped acres inside the town line, 40.5 percent is well drained and another 39.5 percent is excessively drained, with Canton fine sandy loam and Windsor loamy sand among the most extensive soil series. The USGS separately found that more than 41 percent of the South Merrimack quadrangle is sand or gravel deposited by glacial meltwater.
Coarse ground moves water fast. The town notes the flip side of that plainly: soils with severe limitations for septic systems cover approximately 70 percent of Merrimack.
Where the water actually goes
Elevations run from several hills over 450 feet in western Merrimack down to under 150 feet along the Merrimack River, over rolling terrain with slopes mostly between 0 and 15 percent. The 100-year floodplain covers about 2,204 acres, and the town’s Hazard Mitigation Plan states that “the Island Drive area of Merrimack is particularly prone to flooding.”
This is not new. The same plan’s historic record includes a March 1977 ice jam on the Souhegan River with the impact recorded as five homes flooded in Merrimack. The USGS gage on the Souhegan at Merrimack drains 171 square miles and has a peak of record of 16,900 cubic feet per second.
Wetlands account for 509 acres, and the town defines wetlands as areas of poorly and very poorly drained soils, protected through its Wetland Conservation District.
What it means for a basement here
Ground that drains quickly is not the same as ground that keeps water away from a foundation. Fast-moving water still has to go somewhere, and a foundation is an obstacle in its path.
Worth knowing about the housing too: Census figures put Merrimack at 11,145 housing units, with 33.3 percent built before 1980 and the largest single cohort built in the 1980s. Foundations of different eras were built to different expectations.
All of that is town-level. None of it tells us what is under your house, and we would not quote a job off it. Somebody comes and looks first.
Where the drinking water comes from, and why it matters
About 85 percent of Merrimack takes its drinking water from wells, and the town’s stratified drift is the productive aquifer. The USGS records saturated thickness of stratified drift across this planning area ranging from under 20 feet near aquifer boundaries to more than 100 feet in the Souhegan and Merrimack valleys.
That is the same material a foundation sits in. Ground that yields water to a well is ground that moves water past a basement wall.
Merrimack holds 95 NFIP policies with $22,316,200 of insurance in force, and has recorded 51 paid losses totalling $1,205,852 along with 8 repetitive loss properties. Repetitive loss is the number worth noting, because it describes properties that flooded, were paid out, and flooded again.
What our customers say
603 basement solutions were fantastic to work with! They were creative in help problem solve some significant structural problems. The “power post” footings are exceptionally well engineered and were the best solution for my crawl space. Friendly knowledgeable staff who worked hard rain or shine and in cold or hot conditions. We would highly recommend
helen and sean franchi, 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 Merrimack
- Basement waterproofing in Merrimack
- 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 Merrimack
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 Merrimack and the surrounding towns from our shop in East Kingston, New Hampshire.
Common questions about crawl spaces
- How much wood moisture in your crawl space can you tolerate
- How to get rid of moisture in a crawl space
- 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
More 603 services in Merrimack
- Basement Waterproofing in Merrimack, NH
- Basement Finishing in Merrimack, NH
- Foundation Crack Repair in Merrimack, NH
- Radon Mitigation in Merrimack, NH
