Full-Depth Blocking Between Floor Joists 2

[ChiEngr]

Hello everyone,

I am looking for some help with the following:

Plumbing contractor cut through the entire depth of some floor joists supporting the bathroom at the 2nd story of a 2-story house. I am working on a repair detail that involves lowering the ceiling (ceiling heights were very tall to begin with), and installing new joists beneath the compromised joists. I plan on putting in full depth blocking between joists at a couple of locations to ensure that the existing and new framing members are tied together, for lack of a better description. My question is: are there any recommendations for how to connect the blocking to the existing wood floor decking? Any nailing or screwing into the 1/2" or 3/4" thick deck does not seem to be feasible. Has anybody used an alternative like liquid nails for a condition like this? I don't have the ability to nail down from the top as the owner does not want to remove the tile in the bathroom.

Thanks in advance for your insight.

 

[phamENG]

Can you post a sketch? I'm not clear on what you're doing. Based on the description of the problem, the typical solution is doubling up the joists on either side (if required) and heading off the damaged joist.

 

[KootK]

In the scenario that you've described, I believe that you want to accomplish two things:

1) Reinstate vertical support which you've done and;

2) Set things up such that the sheathing provides lateral torsional buckling restraint to the new joists.

#2 is what I'd be using the blocking for. I'd do it like this:

A) Use snug fitting blocking of a depth greater than the depth of the original joists if possible. This way it will engage the top edge of the new joists.

B) Toe nail the blocking into the original joists (and new ones if space permits).

C) Do not attempt to connect the blocking and the sheathing directly.

 

[ChorasDen]

Agree on a request for a sketch, if I understand what you are saying, how do you intend to brace the compression edge of the joist, if the new joists are installed below the existing joists, curious how you will provide bearing.

 

[Celt83]

For the blocking to existing sheathing attachment take a look at the Simpson A35 with their newer PH612I fasteners:

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[phamENG]

Celt - neat. I hadn't noticed that configuration before. Thanks for highlighting it. That'll come in handy...

 

[ChiEngr]

KootK has described the situation perfectly. I am also attaching osb on each side of the joist "assembly". That should help transfer the vertical load from the existing joists down to the new joists - I do not want to assume there will be uniform bearing surface at the interface between each member.

Celt - thanks so much for sharing that product. That is exactly what I am looking for. Given how the existing construction looks, I would not be surprised if the existing joists are adequately attached to the decking/diaphragm.

 

[KootK]

In some situations, it might be advantageous to run the new framing perpendicular to the old and just connect the two joist systems with hurricane ties or something.

 

[gte447f]

I'm curious, why are you attempting to frame a fix underneath the damaged framing instead of in-plane with the damaged framing, which seems more typical as phamENG has said? Is it to preserve the plumbing lines that caused the mess to begin with. If so, instead shouldn't the plumber have to remove all of the offending lines, allow the framing to be repaired in-plane, and then re-install the plumbing lines below the framing? That seems like the proper punishment or penance for the plumber, how ever you like to think of it.