How to Cut Blue Foam Insulation Board

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What You'll Need
Blue Foam Insulation Board
Tape Measure
Long Ruler or Board
Utility Knife

Foam insulation board is an excellent insulation material with a high R-value. While it is not perfect for every individual situation, it is a very good option for unfinished walls or walls that have not been finished yet. Additionally, it is relatively easy to work with and install if you know the proper techniques, usually only requiring a commercial adhesive product. However, in order to install a foam board to insulate your home's walls, you will have to cut it first. Fortunately, cutting foam board only requires a utility knife and measuring tools and is quite simple if you prepare correctly.

Taking Accurate Measurements

It is very important to take accurate measurements when cutting foam board. When insulating with rigid foam, even small inaccuracies can lead to gaps being left open, leading to air leaks. Because of this, you will need to be sure your measurements are precise.

Use your tape measure to take measurements of the area you will be installing your blue foam board into. Next, lay your foam board on the ground with the waste side up. Measure off the same amount of blue foam insulation board. When you are sure you have the measurements as close to perfect as they can get, mark your foam board off with your marker.

Scoring the Foam Board

Next, get out whatever tool you are going to use as a straight edge. It could be a long ruler, yardstick, extra board, or anything long enough to extend beyond the length of the cut you will make. Line up your straight edge with the marks you have made previously.

Once you have done this, use your knife to score the foam board. Because you put the foam board waste side up in the previous step, you should be cutting on the waste side, not the material side. Go from end to end, using your straight edge tool as a guide to making sure you make a perfectly straight line with your knife.

Separating the Foam Board

Once you have scored the foam board from end to end to your satisfaction, set it upright. Depending on the size of your particular piece of foam insulation board, you may wish to enlist the help of a friend for this step. Regardless of how many people are involved, you will need to hold both ends of the foam insulation board firmly so they do not move. While you are doing this, push firmly on the section of the foam board that you scored. You should be able to snap the foam board cleanly into two pieces along the line by doing this.

Finishing Up

If everything has gone as planned, you now have a nice clean cut in your foam board. However, it is likely that things have not gone perfectly. Before you install your foam insulation board, take the time to clean up the edges with your utility knife.