Adjusting strapping over foam
stevenschristianj
| Posted in Construction Techniques on
When installing strapping over continuous exterior insulation, what is your preferred method for adjusting the strapping to get a nice flat plane for siding? I’m thinking a string line run from corner to corner would be most effective? I’m working with 1×4 over 3″ of EPS
Replies
I'd say it's a little late in the game to be creating a flat plane. That said, I'd run strings in a X, corner to corner- they should just touch in the center- it's an old doorhangers trick- when they touch, they define a plane. (They define 2 triangles, which are planes by definition. If those 2 planes touch on 2 sides, they're co-planar. QED)
I'd install the foam, then run the strings off the ends of 2 straight 2x4s, one at each end. Then you can evaluate the planarity of your foam by moving another straight 2x4 ( or short chunk of 2x4) around, If there's a gap between string and 2x4, you have a divot. If the 2x4 interferes with a string, you have a bulge. You can run auxiliary strings at the top and bottom to help with gauging there.
To help with sighting for planarity, use "winding boards." Attach one straight 2x4 at one end and stand where you can sight across the surface of the 2x4. Have a helper move another straight 2x4 along the surface and note how its edge lines up with the stationary 2x4. Again, an old doorhanger's trick to be sure the jambs are parallel. Simple & crude, but surprisingly effective.
Based on what you find, decide where you want your strapping plane to be. Basically, all the strapping should be even with your biggest bulge. Say it's 3/8 below the strings & your 1x4 is 3/4 actual, a total of 1-1/8. Create a 3/8 gauge and shim all your strapping so it's 3/8 below the strings.
Unless your wall is really framed badly, you could do like most siders and just slap the strapping up. Sight along your wall and see if you really notice any bulges or divots and remember you're being 3 times as picky as most observers.