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Community and Q&A

Sill plate sealing

the74impala | Posted in Energy Efficiency and Durability on

This is a picture of my sill plate.  They have a sandwich of fiberglass under there.  What about the holes in the top of the block. I was going to spray it with a froth pack, but should I put a board over the open cinder block first?  Is the fiberglass going to wick moisture in and cause problems?


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  1. GBA Editor
    Brian Pontolilo | | #1

    Hey Tom,

    I haven't encountered either of your situations, the fiberglass under the plate or the open CMUs. I assume that your intention is to air seal and insulate? If you are going to use a spray foam kit, my thoughts are to friction fit pieces of rigid foam into the block and and pull back the fiberglass and then spray the foam on the top of the block, onto the plate, and around the rim area so that it is continuous. I'm curious to hear what others may have done in this situation.

  2. the74impala | | #2

    My first thought was cut foil face iso to good fit just shy of the inner edge of the block. Caulk adhesive on top of block. Place the iso and foam over all of it to inner edge of block.

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