Floor Framing – Part 3

Now that the joists have been placed and nailed we begin the sheathing of the joists. Sheathing will add stability to the joists and allow us to frame walls on top of it.



Before we begin the sheathing let’s talk about types of sheathing. The most common sheathing would be 3/4″ tongue and grooved OSB (oriented strand board). Another type of sheathing is 3/4″ tongue and grooved plywood. The common thread here is tongue and grooved which provides stability at the ends of the sheathing material between the joists.


Either type of sheathing is adequate for the floor – the driving factor is typically cost of the material. This is why OSB is typically chosen for most residential projects.



Another issue involved with floor sheathing is how the floor is attached. Several methods of fasteners are nails, staples, or screws. I personally like screws for their ability to resist pullout. Staples and nails provide this resistance with glue that is typically placed on the surface of the nail by the manufacturers.



No matter what the type of fastener chosen the sheathing should be glued down. I typically choose PL-400 or Liquid Nails. Floor adhesive along with using screws will stop most, if not all, floor squeaks down the road.



Now on to the actual sheathing of the floor. We begin at a corner that we can place a full sheet of OSB where the 8′ length of the sheathing will run perpendicular to the joists.



The first piece will allow for a double check on how square the framing was installed. If you’ve done the layout correctly when placing the sill plates you shouldn’t have any problems.



With the tongue and grooved OSB there will be several times where you can’t get it tight enough. If this happens I will use a sacrificial rip of OSB with a 2×4 and a hammer to beat it into place. Don’t confuse a hard to install piece of OSB with the 1/8″ expansion gap that will be present on most tongue and grooved products.



A major point to remember when installing consecutive rows of sheathing is that you will want succesive rows to split between the previous rows. So starting the first row with a full sheet the second row will be a half sheet and alternate each row as you continue.



When you get to an edge (or end of a row) I typically let it overhang a little bit (up to 4′) and then come back later and snap a line to cut it off. You don’t have do this but I find that it saves time and allows one individual something to do during a slow time in installation.



Wrapping up the installation of the floor sheathing is as easy as making sure all the screws were installed correctly, ends were trimmed, and all openings were cut out.



If there are any questions please contact the webmaster or ask the question at the Home Construction Forum. The next series of articles will deal with wall framing.

local_offerevent_note December 18, 2020

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