How to Cut Foam Insulation

Insulation increases the R-value (a measure of thermal resistance) of your house and reduces drafts. You can add foam insulation to areas or walls that need extra protection. Cut pieces of foam insulation (less than 2 inches thick) to fit these areas using a drywall T-square and sharp knife or razor blade.

Things You'll Need

• Measuring tape
• Pencil
• Foam insulation
• T-square or long straight-edge ruler
• Sharp knife or razor blade

Instructions

1. Measure the area you want to add the insulation. Make the measurements on the foam insulation and mark with a pencil.

2. Lay a drywall T-square or long straight-edge ruler along your measurements.

3. Use a utility knife or razor blade to cut along the T-square. Do not try to press the knife all the way through the insulation. Just make a shallow cut to "score" the insulation on one side.

4. Remove the T-square and stand the insulation foam upright.

5. Apply gentle pressure to the back of the insulation, holding the edge. Press along the cut line until the insulation snaps. If cut correctly, the insulation should break cleanly and evenly along the cut line.

6. Repeat the above steps to make additional cuts or to reduce the size of the pieces.

Tips & Warnings

• Foam insulation snaps very easily. Be careful when making your measurements and scoring the foam board so you do not accidentally break off a piece.