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“I have a project I have been working on for 5 years. I am building a 2800 square foot ICF first story and stick-framed second story house in Northeastern Washington, a dry climate with snow in the winter. The first floor walls have been up for 4 years, and I am planning on finishing the house in the next year and a half. I have noticed that ants seem to love the foam for a raceway behind some pieces of tar paper I had up. I didn't put any waterproofing on the outside of the walls because the soil is clay, the slope is away from the walls on all sides and there is a slab on all of the first floor. The supplier of the blocks said I didn't need to waterproof the walls. I am not concerned about water, but I am concerned about insect penetration fo the house through the ground. Am I going to have to dig up the back fill around the whole house and clean the block and seal it from insects, or is there another adequate solution?"
Hate to tell you this, but what the supplier told you is WRONG. They were probably thinking that if you added the cost of waterproofing etc., you might back out of using ICF altogether. Instead, your supplier just cost you a bunch of money. About the only way you will eliminate the bug factor, and get peace of mind, is to dig up your basement, clean off the foam, and apply a peel and stick membrane like WR Meadows MelRol, or Polyguard’s 650LT. Be sure to use a water base primer on the foam and not solvent base. Apply the membrane from at least 6” below the wall, or over the top of your footing, and down the edge up to within an inch or two of finished grade. You may want to install an aluminum termination bar along the top edge. The termination bar helps out with screeding stucco, etc. over the foam which you will need to protect the exposed area of foam. Don’t run your siding down to the grade. This is just another shortcut for ants, termites, etc. to get up the wall and start nesting behind your siding. Another “SORRY IT’S TOO LATE” saga. Hope all turns out well in Northeastern Washington!