Call me persnickety, but I like to place a nice full bead of construction adhesive down the center of the floor joists before I lay down a sheet of plywood subflooring. Too many times, I’ve been on a job site where the glue was applied carelessly, resulting in an erratic line with skips and unacceptably thin smears. If it’s worth the expense and effort of gluing a subfloor in the first place (and I think it is), then it’s worth taking the time to do it right. The device shown in the drawing is my solution to the problem. I think the best part is that using this gadget, I center the glue bead on the joist every time without having to go back.
The glue sled, as I call it, is nothing more than a 1-5/8-in. wide block of 3/4-in. pine with a hole in it. The block is sandwiched between 1/4-in. thick plywood sides. The hole accepts the nozzle of the glue cartridge, and the rubber band loops over the caulk-gun frame, holding the sled in place. In use, the plywood sides ride along the sides of the joist, keeping the nozzle centered.
I think a 3/16-dia. bead of glue is the ideal amount. And although I don’t obsess over this detail, I can tell you that cutting the nozzle 3/8 in. from its tip yields a 3/16-in. opening for the glue to exit. If your joists are on 16-in. centers, figure on using about three-quarters of a 10.5-oz. tube per sheet of plywood. Where sheets come together on one joist, you can get a fairly even off-center bead of glue by lifting up the sled and angling the glue gun to the side.
—Herrick Kimball, Moravia, NY
Edited and illustrated by Charles Miller
From Fine Homebuilding #146