I am starting to install polyiso on the interior of my slanted cathedral roof assembly and am having trouble finding the studs through the 4.5" of polyiso that I have. Things working against me:

  1. not all studs are perfectly 16" OC.
  2. The ceiling deck is at an angle.
  3. When I place the screws in it's hard to get them into the studs or even find the studs with the angle of the ceiling.

Are there any videos or techniques that can help me find the studs...I'm at a loss here!

  • Are you screwing up drywall over the insulation, or just screwing the polyiso up?
    – HerrBag
    Mar 11 '13 at 13:55
  • I am screwing up drywall over the polyiso (you have to fo fire code). I will be putting some strapping in between to make it easier to install the drywall.
    – user11988
    Mar 11 '13 at 16:26

Never installed polyiso but if I was presented this issue this is what I would do.

I would go one sheet of polyiso at a time and find the studs on the ceiling before I put the polyiso up. Measure the distance of the studs from the edge of where the polyiso will be stalled and then mark the polyiso with those messurements. Use a chalk line to give a nice straight line where the studs will be on the polyiso. Installing will be simpler this way.


Some guesses:

Thermography might be able to map the rafters with the right environmental conditions: Cold outside temperatures/warm inside

Another guess: Ultrasonic emitter/receiver pair, one roof side, one from inside.

Third guess: Map the rafters from the roof side with conventional stud finders. The thickness there, even with roofing, might be better than from the underside.

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