How to Insulate Hollow Concrete Block With Spray Foam

Drill holes in the center of the hollow concrete block walls using a masonry bit. The size of the hole needs to be slightly larger than the tip of the spray nozzle on the applicator gun. Place the holes in the center of each row of blocks, spaced every 3 feet vertically.

Rock the tanks to mix the solutions in the tanks. Since the foam needs warm temperatures to expand properly, only use the spray foam kit during summer when the temperatures are between 75 and 85 degrees Fahrenheit.

Put on the safety suit, goggles, gloves and respirator. The expanding foam sticks to everything.

Attach the hoses to the tanks, following the directions from the manufacturer. Use the wrench included with the kit to tighten the connections.

Cover the face of the application gun with petroleum jelly. Snap a nozzle in place on the gun. Several nozzles usually come with the kit. Change them out as they become clogged.

Open both tanks completely since the combination of the two mixtures chemically react to form the foam. You want both tanks to flow simultaneously.

Press the nozzle into the lowest hole and press the release trigger to start the flow of liquid foam. After about 30 seconds, pull the wand from the hole to do a quick visual check on the level of foam. Place the nozzle into the next hole up and repeat until you have filled all the columns of block with the foam. You will see it expanding through the drilled-out holes.

Clean off the excess foam that extrudes from the drilled openings by cutting it off with a scraper.