Pests Carpenter ant

Published on May 17th, 2018 | by Henri


Eliminate carpenter ants before insulating band joists

Q.  I have a question about insulating the rim joists (band joists) of my 100+ year old house. It seems that there is sawdust in the space above the foundation, against the joists above the sill plate, and plywood covering it. Should I remove the plywood and sawdust, and place the extruded polystyrene directly against the joists? Am I OK to simply add the foam insulation to what is there? Obviously option 1 will be messier and much harder, but is option 2 the correct method? Thanks. Hyde Park.

A.  I am not clear about the plywood covering the sill plate; what is it doing there? But the sawdust you see is almost a sure sign that carpenter ants are nesting in the sill plate or the joists (which I assume may be logs in a 100-plus year-old house).

Carpenter ants do not eat wood, as do subterranean termites; they excavate it to build nests and they usually choose wood that is moist. As my late old friend, a well-known entomologist told me years ago in his usual humorous style: “Carpenter ants are a homeowner’s best friend; they tell you that you have a leak somewhere.”

The damage they cause may become structurally substantial over time. Consider having a licensed pest control professional investigate and treat these spaces before more damage occurs if the infestation is still active.

Carpenter ants will drill holes through foam insulation to get to their choice of nesting places. You need to clear the problem before using any type of insulation on your band joists.

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