How to hit studs with 4.5 inches of interior polyiso?
NBABUCKS1
| Posted in General Questions on
I am starting to install my 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!
Kevin
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Replies
Kevin,
First of all, the framing members that you are trying to hit are called rafters, not studs.
Second, it would have been best to mark the rigid foam with chalk lines or a black marker as the foam was installed. Hopefully you have some type of marks on the foam. If not, you can measure 16 inches on center or 24 inches on center from one of your "good" screws.
The key to hitting the rafters is to make sure that your screws are perpendicular to the plane of the foam. Some builders have a good sense of perpendicularity, while others just don't have the knack. If you pay attention when you are driving the screw, however, you should be able to improve your ability to drive a screw at 90 degrees to the foam.
You're right, however, that this type of fastening is challenging and frustrating.
Finally, once you have the foam tacked in place with cap nails, it's a good idea to install 1x4 furring strips to hold up the foam (using long screws, of course). That will make it a lot easier to install the gypsum wallboard.
Martin, thanks a ton you've been great through this whole process.
I did a bit more research using rafters as my search term instead of studs and found this...
-Install 3/4" deep furring strips perpendicular to the rafters 24" OC. This is to create an air gap to make the polyiso's radiant foil work better
-Attach the polyiso boards to the furring strips
-Seal between the polyiso boards with some kind of vapor barrier tape (aluminum tape? house wrap tape?)
-Attach another set of furring strips to the polyiso boards (on the inside side of the room this time). Again to create a small air gap
-Attach drywall to the furring strips and finish the drywall.
I think this is the easiest route and I"m willing to spend the extra bit of money to make this process a little easier.
Any problems with the vapor that could get trapped between rafters (sealed and caulked with XPS) and polyiso (where the top set of straps/furring strips are)?
Not sure if I should start a new topic for this question but..
How do I properly install light fixture and ceiling fan fixture junction boxes when I am installing them in 4.5" of polyiso? I need something rigid to mount them to.