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Question DetailsAsked on 3/25/2014

Should I do a proactive termite treatment before encapsulating my crawlspace?

When I bought my house, the termite inspector said there was no evidence of prior termite activity and that was rare for my area. I'm about to get my crawl space encapsulated and just got a new termite inspection. The inspector found no evidence of termites but recommended a proactive treatment before sealing up the walls.

The encapsulation will leave a viewing strip for future inspections. The treatment would cost $600. If needed later, there would be additional cost to work under the encapsulation (plastic and foam board insulation). Googling "proactive termite inspection" gives results for pest control companies only, no independent sites making this recommendation.

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8 Answers

Voted Best Answer

IF you have not had prior infestations, AND your entire foundation is concrete or concrete block or brick with no wood in contact with or within 4-6 inches of the soil, then I do not see why you need to treat the crawlspace area - your "perimeter defense" zone now moves to the outside wall of the house.

Note - the encapsulation should never seal around wood like support posts so they are connected to the ground - it should seal off around their base, around concrete - assuming you mean you are doing an on-ground sealing. If you mean encapsulation with foam and plastic going on the underside of your flooring joists, then I would have the wood posts (if any) first treated with heavy-dosage brush-on penetrating "permanent" insect preventative like a copper napthalate solution and spread borax powder around the bases of the posts as a preventative - much longer acting than typical termite preventatives applied by pesticide companies.

Personally, if I lived in a termite-heavy area, I would be routinely maintaining a perimeter spray-on foundation wall treatment plus in-ground injection treatment, assuming the primary infestation mode in your area is by burrowing (sub-terranean) rather than flying (drywood) termites.

For info from sources other than pesticide companies on proactive treatment, google a search phrase with the words termite and USDA - also termite and Forest Service - and you will find many articles on termites, how and where they lie and nest, and preventative and response measures to control them.

Answered 6 years ago by LCD


The encapsulation will be a complete vapor barrier on the floor and most of the way up the walls, with foam board on the walls on top of the vapor barrier. There will be a 3" termite inspection gap at the top.

The walls are block and brick, and all piers are brick. No wood is within 6" of the floor.

Thank you for your answer! I think I'm going to get an opinion and price from another termite company before making my decision. The first guy did say this treatment would probably last 10-15 years and I do see the sense in having it done before encapsulating.

Answered 6 years ago by 1955ranch


One recommendation - not directly related to termites, but similar - is carpenter ants and a few other types of ants LOVE to tunnel in styrofoam, even more than wood. They do not eat the wood (or styrofoam) - it just provides something to tunnel and nest in, and to provide a secure protecction for their highways. I always recommend underlaying (on the dirt side - or plastic sheet in your case) foam board with Ortho insect powder - the all-ant killing perimeter wall type - as a preventative. There is also a spray type that is long-lasting. At least around the perimeter - that way it is also not in the way in case a worker needs to crawl under there in the future. If treated, be sure to put up a warning sign at or just inside the crawlspace entrance that will last, specifying what treatment was used, by whom (company name), when, and where in the ground-plastic-insulation sandwich it was put.

Since you are running board up the foundation wall, I presume this means you are turning this into conditioned air space, and therefore tightly sealing off ALL screening and such from the outside ? If not, that exposed board is a risk, as ants can get through screening and around pipes and such, and if the crawlspace is going to be open to outside air, the foundation wall board does very little good.

Personally, I am not convinced of the benefit of a crawl space termite treatment which for the cost would certainly be an in-soil treatment. It seems to me the best place for that is OUTSIDE the foundation wall, where it protects the entire house.

Answered 6 years ago by LCD


Correct, this will be a conditioned space with a new supply installed to condition it. The foundation will be completely sealed. Good tip on the ant repellant. What I am most excited about pest-wise is the reduction of spider crickets.

I'm going to have a radon mitigation pipe laid under the liner as well since I live in an area with high radon. (My pre-test came back 2 pCi/L but with the vents sealed I expect that will increase.) My goal is not to have to pull up the liner for other jobs once it's installed.

Answered 6 years ago by 1955ranch


Closing off ALL outside openings should keep the crickets out, but whether they lay eggs in crawl spaces that could hatch out another generation in that environment (under the plastic) I do not know - ask pest control man. And whether they can chaw through the plastic to get out.

Good thought about the radon issue, but if the plastic liner is being properly physically clamped to the foundation wall, that should take care of the issue, I would think. That is standard practice for crawlspace radon control, though running a stack pipe to maintain a negative pressure under the plastic would be a standard procedure.

However, with that situation you might want to consider raking out any rocks and pebbles in the area and having them place a 1/2 to 1" layer of DRY (to prevent mildew smell) masons sand first, so workmen placing the insulation board and any future workmen do not puncture the plastic sheeting. That is a good practice anyway, because of the likelihood HVAC or plumber or electrical contractors might have to get in there in the future, and of course occasional pest control inspections, and laying on the board could cause sheeting punctures. Another alternative which might work as well and be cheaper if low headroom, is a thick non-woven geotextile filter fabric as a cushion, after raking all larger particles out.

Good Luckk with the project, and may you enjoy many years of lower utility bills.

Answered 6 years ago by LCD


Be sure to leave an inspection area between any foam and the wood framing. They can burrow right through the foam as referenced and you won't even see the damage.

Answered 6 years ago by WoWHomeSolutions


Thanks LCD and WoWHomeSolutions for the info. I called another termite company and they said if they give me a clean inspection, they only recommend an exterior treatment which is $133 vs. the $600 the other company wanted for a full proactive treatment. I am going to go for the $133, which is line with LCD's initial response that the exterior becomes the perimeter defense area.

There will be a 3" viewing strip between the liner/foam and the wood for future inspections.

It turns out there is one piece of wood about 3" from the earth - the sill of the crawlspace entry door. Any recommendations for making that termite resistant?

Answered 6 years ago by 1955ranch


Treat the sill with a copper wood treatment solution - copper napthalate or similar - go by designations like ACA, ACC, CCA (now phased out), ACQ, and copper Azole - about $15 for a quart bottle at Home Depot and others. Normally used to treat deck boards in contact with the ground and in-ground deck support posts. Several coats brushed on, and very wet brushed so it soaks in between the concrete foundation and the sill should do it. Let dry 1-2 dry days between coats or it will stay sticky for years.

I would also have the perimeter treatment - which sounds in the right price range by the way, as did the full-crawlspace $600 number - sprayed heavily in under the sill board and on the ground right inside the entry hatch as well as outside it.

Answered 6 years ago by LCD


I wanted to follow up and say thanks to all who answered my question.

I called around, and another termite company said that their recommendation after a clean inspection was an exterior granular treatment which comes with a one-year warranty against termite damage for $133. I decided to go for that, and I'm very glad I did. The technician agreed that there was no evidence of prior termite activity, and he told me that there were multiple sets of holes drilled in the block foundation, indicating that a proactive termite treatment had been done at least twice in the past. (I guess it's also possible these were weep holes related to water drainage, but he sounded pretty sure.) In any case, I'm glad I went with the $133 treatment instead of the $597. Thanks for the advice.

Answered 6 years ago by 1955ranch

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