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So I had closed foam insulation installed after my electrical work is complete and as an after thought, i started questioning how is it that the wire is safe/protected from nails and screws.

When using baton insulation there is a fair amount of free movement of the wire between studs. In this case when putting a nail or screw through the drywall, the wire is reasonably safe from damage as the wire will just push back or to the side of the nail/screw.

With spray foam insulation the wire is secure in place and has no give, even between studs. When someone nails or screws (although it would need to be longer nails/screws) the nail would pierce the wire.

Given this how safe is this and should there be other considerations taken when using spray foam installation?

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    Get a stud finder that can detect electricity to make sure there are no wires right behind where you want to put a screw/nail and call it day. – statueuphemism May 31 at 15:09
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    I have seen screws go straight through a cable to short the two conductors together - even though the cable was free to move sidewys. The point of the screw spears the cable perfectly... – Solar Mike May 31 at 15:25
  • Don't use excessively long nails/screws. – Ecnerwal May 31 at 15:30
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Code requires the wires to be attached 1-1/4” away from the face of the stud. By the time you add sheetrock or plaster that provides 1-3/4” of free space for any nails. Even with this space occasionally wires get pierced with any kind of insulation even no insulation as is common in interior walls.

Your best safety is to not use long fasteners in the future. You knowing there is a possibility of damaging a wire is part of the safety for the future. Getting a stud finder with a voltage alert so you will know when extra caution needs to be exercised.

The last step if you don’t have them is adding AFCI circuit breakers. These breakers if you don’t have them detect arcing from damaged wiring and open the circuit.

So in short there is not much difference in foamed in verses nothing if proper length fasteners are used.

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  • Thanks for the detailed input! I’ll rest more comfortably! – Oldoldhouseguy Jun 1 at 12:47

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