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How to Cut Rigid Foam Insulation for Basement Rafters

  1. GmaGoldie profile image85
    GmaGoldieposted 4 years ago

    I have the pink rigid foam insulation which I wish to cut for the exterior of my basement walls in the rafter area.

    1.) What is the best method to cut this foam board - with an utility knife?
    2.) The first area I am working on is just for storage, can I simply cut for the rafters? Would the foam just in the rafters be worth the effort of all the various cuts? My plan was to cut each one for these small spaces and then add the foam around the perimeter of the foam to completely seal. I think are floors are very cold because this space is open.

    Thoughts, suggestions?

    1. Rain Defence profile image97
      Rain Defenceposted 4 years ago in reply to this

      Just use a normal handsaw. The best bet is to measure the space then score the board with a straight edge first. If you make it a tight fit you can just wedge it in. It's very easy to cut through with a saw, but you'll probably want a face mask as you don't want to be breathing the stuff in.

    2. purenrg1 profile image60
      purenrg1posted 4 years ago in reply to this

      Why are you using foam board. in the rafters. you  may not get an acceptacble R value with Foam . encapusated fibre glass is much better and easier to install with very little cutting. With foan board you really do  not need a mask but use one to be on the safe side.  Definitley use a mask with teh fibre glass

      1. purenrg1 profile image60
        purenrg1posted 4 years ago in reply to this

        Follow up. Just re read your inquiry . Is your basement un heated?
        Important to know.

  2. William Mahaffy profile image61
    William Mahaffyposted 4 years ago

    Like others have said, I would install some fiberglass batts instead of the foam.  If you're insistent on using the foam, then you can cut it with either a normal utility knife or the safe method, a hand saw.

    Also, make sure you look out for pipes or wiring in the rafters when you're installing your insulation.