How to Stop My North Wall in My Non-Heated Garage From Getting Condensation

Inspect all walls of the garage thoroughly to locate any gaps or cracks larger than 1/4 inch that extend to the outdoors. Pay particular attention to the areas around windows, vents, pipes and other openings. Fill all gaps and cracks with expandable spray foam by half, which allows room for expansion.

Open a tube of silicone caulk and apply a 1/4-inch wide bead around all windows, doors and vents to ensure no air seepage occurs. Smooth the caulk bead with your finger after application to create a professional appearance.

Measure the height of the north garage wall using a tape measure. Lay a sheet of 1-1/2 inch thick rigid foam board insulation on a table and measure the height to the same measurement as the wall. Cut the board, if needed, using a utility knife.

Apply silicone caulk to the back of the board in a zigzag pattern and then run a 1/4-inch bead around the perimeter1 inch from the edge. Turn the board vertically and press it into one corner of the garage, flush against the north wall. Hold a level beside it to ensure it is even and insert a wood shim under the bottom edge if it is not. Hold the panel for 60 seconds to allow the caulk to set.

Cut and position a second piece of rigid foam insulation directly beside the first in the same manner, adhering it to the wall with caulk.

Cut a wood furring strip to the same the height as the boards using a table saw. Place it in the groove where the two boards meet.

Insert a 1/4-inch wide drill bit into a drill and create 2-inch deep holes in the furring strip every 6 to 8 inches. Insert 2-inch screws into each hole using the drill and a screwdriver bit to secure the strip in place. Use masonry screws if the garage is cement or block, and use wood screws otherwise.

Continue installing boards and furring strips all the way along the north garage wall, or on all walls of the garage if you prefer.