I need to install crown moulding in a large room. Now you could use a stud finder and find all the studs in the walls and mark them (but then you’d have marks on your walls). You’d also have to find all the ceiling joists and mark them as well. Of course, you’d inevitably have the problem of missing a stud or joist here and there and having to pull a nail, try again, and then putty two holes. That’s a lot of work.
I thought it would be so much easier to have a nailer behind the moulding. Unfortunately, to my amazement, they don’t make any such thing. Why, is beyond me, but I decided it couldn’t be that hard to make my own.
The bad news is figuring out how to cut the nailer is a little tricky (but that’s why I’m posting this article), but once you know the cut dimensions, the rest is a piece of cake.
NOTE: This article assumes 3-1/4″ wide moulding. Your dimensions will need to be adjusted for wider moulding.
I started by measuring the moulding an creating a model to those dimensions in Sketchup (see figure below):
Now, if you have crown moulding that is 45° angles on both ends, this is much easier. The 52°/38° design is a common moulding configuration, however. The problem with this is that most table saws won’t cut past 45°. No worries.
You really don’t want to try to get as “snug” a fit as is pictured above anyway. There needs to be a relaxed enough clearance that the moulding will still fit tightly against the wall and ceiling in spite of inconsistencies in your cut or bumps in your wall. I would aim for 1/16″ to 1/8″ inch clearance between the moulding and the nailer strip.
You’ll notice the Sketchup tool measures the back side of the nailer at about 1 1/16″ inch. Actually, I found this to be about the ideal measurement for a relaxed fit. I set my table saw at about 1 5/16″ and after two cuts was left with 1 1/6″ as pictured below.
You’ll notice the fit is perfect even though the angles aren’t perfect. As mentioned previously, my table saw can’t cut a 52° angle. I set the table saw at 38% and made the first cut.
You can use 3/4″ plywood if you like. I used cheap econo-grade 1×3 lumber. However many boards you need to cut, make all the 38° first cuts. Then set your table saw to 45° (which is as close to 52° as you can get), flip your boards over with the 38° angle against the fence and make your second cut.
Now that all your pieces are cut, you’ll notice in the Sketchup drawing that the nailer board needs to stay within 1-1/2″ of the wall on the ceiling side to leave room for the crown molding. Take a 2×4 block, lay the wide side again the wall, so the 1-1/2 edge is against the ceiling and mark the edge on the ceiling with a pencil. Do this every couple of feet. Place the 38° angle side of your nailer against the ceiling, putting the edge right on your pencil mark and screw to the wall plate.
It’s a good idea to pre-drill your nailer strip so it doesn’t split. I would also use 3-inch drywall screws instead of wood screws for the same reason. If you’re using 8-foot nailer lengths, one screw at either end and one in the middle should suffice. Just make sure you angle your pre-drilled hole so that the screw is hitting the center of the wall’s top plate, and you’ll be set.
Now, you can put your crown moulding up without any worries or tedium over what you’re going to nail to.