LogiVap

Blocking for new subfloor?

I took out my previous subfloor down to the joists, sistered the joists, and am preparing to lay the new subfloor.

Question: Should I install blocking between the joists, at both ends? The sistering has the joists now at about 15" OC.

stickshift

Let's start at the beginning - why did you do all of this?

And the end - what's your desired finished floor?

czizzi

Blocking is used mid span to tie one individual joist to the two adjacent ones this stiffening the floor. ow long is the span? It would determine single blocking or double blocking. Are the sisters contiguous for the whole span without breaks?

LogiVap

This was done because the floor was crooked, so I sistered the joists and made them level. The eventual finished floor will likely be tile.

The span is about 14, and the sisters are 10', so they're about 2/3. I had to remove blocking for the sisters, and I replaced them as I went. I didn't depict it on the drawing, but there is blocking near the middle of the sistered joists span.

Just wasn't sure whether blocking would also be neccesary to support the new subfloor at the ends.

stickshift

OK, so we have span and spacing, can you tell us the size of the joists and what you used to sister them? Also, there's no flooring on top of them at the moment; just the joists?

LogiVap

Good ol fashioned 2x10s, sistered with good ol fashioned 2x10s. I fastened them with adhesive, bolts and nails.

joecaption

If you use Advantech T & G subflooring with constrution adhesive on the joist and #8 ring shanked nails there is no need for "blocking".
What I do is use 2 X 4's laying flat 1/2 way under the walls to stop any air from getting in.

czizzi

For tile, I would definitely add blocking. I've had instances were I had support beams added perpendicular to a floor and could not get it to stop moving. Blocking is what eventually settled everything down.

Also, you want the quietest floor possible, I would screw it down in addition to the glue and if adding a second layer for structural integrity, screw it to the first.

LogiVap

When you say you would definately add blocking for tile, are you referring to the mid span blocking I've already installed?

Or are you saying I should go ahead and install the blocking at the ends of the joists, so that I can attach the perimeter of the new subfloor to it?

czizzi

Both, while Joe's flat 2x4's would work, a standard blocking will be stronger. Does the wall also need support?

LogiVap

Yeah I put quite a bit of blocking/support underneath the wall.

Thanks for the help. I'll start on those blocks. Guess I'll lay the floor next weekend and not tomorrow.