Sistering floor joists in attic - advice?

[Kodi Crescent]

I am working on reinforcing my subfloor in my attic.  I have a section that I need to reinforce.  These are 2x10x12's, and the structural engineer that came out suggested I triple them for the proposed load.

I've cut some access holes to see what I'm getting into, and it seems that the top plates of my support walls below are not fully accessible.  I can get to one side fully, but I'm 3" - 4" off from being able drop my sister joist straight down onto the top plates.  So in order to get to the top plate of one side, I'll have to slide it under 3-4" of subfloor.  There is a wall that covers the 3-4", and I can't remove the wall.

I'm thinking of sliding this in as close as possible, and then beating it into place, or slightly rounding the corners and beating it into place.

Has anyone encountered a situation such as this, and if so, any advice?

Thanks!

 

[Kodi Crescent]

Put it in on its side and twist it upright, then pound it against its mate?  Is that the answer?

 

[tjbnwi]

You'll probably find the existing joists have shrunk slightly.

Lay them on their side, slide them in place, roll upright. Use clamps to draw together, pounding could disturb other things.

You may have to angle cut the joists to clear the roof sheathing. Measure the existing HAP, use that number for the start of your pitch.

The engineer should have specced the nail schedule, do not use screws.

Tom

 

[bigjonh]

You can notch the ends to roll them into place under the subfloor/ wall. The general rule of thumb is 1/4 of depth. Google joist notching and or check with your engineer.

 

[RJNeal]

We did a job in San Franisco where we did a lot of sistering. We use Simpson drive screws on the engineer's spec.
Good luck.
Rick

 

[Kodi Crescent]

It appears my joists have shrunk.  They measure in the 9 - 9 1/8" range.

When I get the new ones to sister, should I let them sit in the nice hot attic (where they will be installed) for a couple of weeks before the job is done?

If they don't shrink to match the existing ones, do I plane them close to flush or leave them at their width?

I'm doing a 9 x 12 area.  Do I need to use tongue and groove subfloor for this area, or will standard plywood suffice?

Thanks!

 

[Stephen B]

It appears my joists have shrunk.  They measure in the 9 - 9 1/8" range.

When I get the new ones to sister, should I let them sit in the nice hot attic (where they will be installed) for a couple of weeks before the job is done?

If they don't shrink to match the existing ones, do I plane them close to flush or leave them at their width?

I'm doing a 9 x 12 area.  Do I need to use tongue and groove subfloor for this area, or will standard plywood suffice?

Thanks!

[size=10pt]
Have they shrunk, or were they originally planed for levelling purposes?

Cannot comment on T@G/ply as not familiar with your building codes.

Edit. The joists may also have been installed as green (ie not kiln dried) timber.

 

[bigjonh]

I think they'll just warp if you leave them sit up there. Just sister them up and plane them. T&G takes some room to install, sounds like your space is tight. If your worried about stiffness you can always run blocking between your joists before you ply.

 

[w802h]

Maybe you can attach your ply to the taller joists and ignore the shorter ones if the span is appropriate, esp. if you go the blocking route.

 

[tjbnwi]

T&G makes the floor diaphragm a monolithic assembly. If you have the room use T&G.

Tom