Is Sealing a Crawl Space a Calling Card for Termites?

Is Sealing a Crawl Space a Calling Card for Termites?

One of the first questions asked about sealing a crawl space is, “What about termite treatment?” This is in reference to yearly inspections for termites and treatment of foundations when signs of termite activity are apparent. Addressing this situation is especially necessary for residents in the southern parts of the U.S. where subterranean termites are such a problem.

Construction Techniques – The Termite protect

An optimally sealed crawl space requires some construction techniques to be implemented to reduce the probability of termites accessing the floor system of a building. One of the long time deterrents to these pests has been the termite protect, and it nevertheless has a use today. The protect is a metal sheet that is placed over the top of the foundation blocks before the floor framing is done. Termites can’t penetrate it as long as nothing punches a hole by it.

If embeds are in the blocks for bolting the mud sill on the top, provisions must be made to seal around those penetrations. The termite protect projects past the concrete block under the building, so once termites make their way underground to the block, they would have to crawl out of the block and go around the protect to get to the wood. However, termites have no desire to exit a damp and dark ecosystem and expose themselves to the light.

Crawl spaces are handled in one of two ways:

Solution #1 – Vented – A thick poly film is placed loosely on the crawl space “floor” to prevent moisture from rising and entering the home. Foundation vents are installed to help remove moisture that escapes by the poly, and insulation is applied to the underside of the floor above.

Problem – Inspections in vented crawl spaces revealed damp conditions, moist floor framing members, and wet insulation. This presented a possible for mold and mildew, decaying wood, and termite infestations.

Solution #2 – Sealed – Ground cover is applied to the soil “floor” and up the foundation walls, insulation board is installed and sealed, and spray cellulose insulation is applied.

Problem – without of ability to inspect for and treat termite infestations.

The insulation of the foundation walls using the sealed method is less costly and more energy efficient than placing insulation on the floor’s underside above the crawl space. If the floor is constructed of open web trusses, the ineffectiveness is already more so using the vented method because a continuous thermal obstacle cannot be produced.

Sealing a Crawl Space

Sealing a crawl space method placing a heavy polyethylene film that completely covers the soil and running it up the interior crawl space foundation blocks to a level that is above the grade of soil at the exterior of the building. Then an insulation board is placed on the foundation and sealed to prevent any moisture from entering the building. The sealer can be a spray-applied form of cellulose insulation containing a borate additive that also serves as a non-hazardous termiticide.

Many homes use the Sentricon bait system for additional protection. This works by placing wood products in special monitoring stations that have slow acting termiticides in them. Foraging termites find these food supplies and take them back to their colonies. The poison has the possible to wipe out complete colonies of termites.

Sealing a crawl space does present a concern regarding the ability to inspect for and treat termite infestations as opposed to vented crawl spaces where the foundation walls are easier to access. Solutions for this are:

  1. Stopping off the ground cover 6″-8″ below the mud sill to create a termite inspection strip.
  2. Injection of the termiticide by the ground cover using a specialized nozzle application technique. The holes produced by termiticide injection are not a breach to the sealed space if the time of action is correctly performed.
  3. Reducing termite access possible by using spray cellulose insulation treated with a borate additive that acts as a termiticide.
  4. Implementing a termite bait system such as Sentricon.

The decline in moisture going into the home in addition as the energy savings possible makes sealing the space under a house a better option than the older ventilated philosophy as long as the time of action is performed properly.

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