How to Adhere Foam Insulation to Concrete

Cut the plastic tip off of the construction adhesive tube using the etched lines located on the tip as a reference. Insert the caulk gun's wire puncture tool inside the tube's tip to puncture the seal. Place the tube inside the carriage of the caulk gun.

Place a 1/2-inch bead of adhesive slightly inside and around the entire outside edge of the rigid foam sheet's back face. Place a few long lines of adhesive across the rigid foam's back face.

Lift the rigid foam sheet, and press the back face firmly against the concrete wall. Place a level on the rigid foam's outside edge to make sure that it is plum. Run your hand across the entire face of the rigid foam to disperse the adhesive between the concrete and foam insulation.

Continue applying adhesive and placing full sheets of rigid foam across the concrete wall. Make sure the sheet's edges butt up tightly across the entire concrete surface.

Measure any exposed concrete that wasn't covered by the full sheets of rigid foam insulation. Lay cut lines out on the rigid foam with a chalk box. Scribe halfway into the foam insulation using a utility knife and following the cut lines.

Bend the rigid foam gently until it breaks at the scribed cuts. Dry-fit the pieces to make sure they fit properly, and make any adjustments if needed. Apply the construction adhesive to the back face of the fitted pieces, and then adhere them to the concrete wall. Continue adhering the pieces to the concrete until the entire surface is covered.

Run strips of insulation tape over any butted edges of rigid foam to create a tight air and moisture barrier.