Blocking between roof joists

[rathersmart]

Hi guys!

I need to add blocking between joists in my garage. Do you have suggestions on where and how to put blocking between the hoists?

I’ve attached a photo of the current joists setup.

 

[larry4406]

Not sure I understand what you are trying to do.

Those look like rafters on a ridge beam vs joists. Also looks like the rafters have been sistered one side, perhaps because the roof plywood did not break properly (land) on the rafters.

Why do you need blocking, to support the plywood edges midway between rafters? I can't see the plywood seams nor any plywood clips which are traditionally used for this.

 

[Dustball]

The question is too vague. It looks like a new ridge beam and new rafters along with old roof decking and old rafters. What's happening here?

 

[The Cobbler]

yes, you need to provide more information . do you mean you need to put blocking at the joints of the plywood?

 

[rathersmart]

The building official did a walk through and advised adding blocking between the rafters to prevent lateral movement.

The original trusses were cut and a ridge beam was added. Then 2x6 were sistered to the 2x4 from the original trusses to provide the load strength required locally.

 

[readhead]

Advised or required?

 

[GTO]

I don't see any trusses there,you have rafters.
Does he want you to put rafter ties in ???

Who uses 2x4's for rafters ????
WTF

 

[The Cobbler]

ok, I get it now, I think
so he suggested blocking at the ridge so the new rafters can't "twist "
would he be open to strapping the bottoms of the rafters at the ridge with 2X to achieve that? otherwise cut a notch in the end of a 2X and toe nail them in is all I can see

 

[readhead]

Everything was already in place before the new ridge. I don’t see a potential for the rafters to roll over. I presume the design was engineered and plans provided to the building department for review. Was blocking indicated on the plans? If not you don’t need to do it. If so then they need to be installed. Don’t let the inspector bully you in to doing something that isn’t required unless he is ready to pay for it. On the other hand, maybe he is just making a suggestion.

 

[GMCGarage]

Put it at mid span, thats the area of most lateral torsional buckling.

 

[strutaeng]

Sure, just rip whatever 2x fits in there. Cut bevel and nail and add adhesive to the plywood.

In the old days carpenter always added block at this location, but rarely do so now, probable because it takes time.

That blocking does in fact prevent lateral rotation at the ends. Also transfer the shear from rood deck across the ridge beam. At the low condition it transfers shear to exterior walls, and down into the foundation.

 

[curiousB]

Just use 2x4 blocks on the flat side. Stagger them on alternate sides of the center span line so you can get a nail gun in to shoot them.


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[The Tool Tyrant]

I assume your goal was to remove the bottom chord of the truss, thus adding the Glu-Lam ridge beam to carry the roof load. Judging from the nail penetrations thru the plywood, I also assume the roof is dried in / roofed.

If the blocking is REQUIRED by code and/ or shown on your plans, simply cut 2x6 blocks to fit between the 2x6 on one end and the 2x4 at the other end (no need to notch for the 2" offset) place them tight to the Glu-lam, toe-nail into the rafters, and also nail into the glu-lam. That's it, nothing too difficult.

 

[Samh]

Am I wrong in thinking that blocking near the ridge would obstruct air flow if there is a ridge vent? Then making it pointless?

 

[scottydosnntkno]

The building official did a walk through and advised adding blocking between the rafters to prevent lateral movement.

The original trusses were cut and a ridge beam was added. Then 2x6 were sistered to the 2x4 from the original trusses to provide the load strength required locally.

If he’s worried about lateral movement, then the best best would be to put your insulation baffles in, and then block (4-8’ apart) with a 2x4 ran on the flat on the ‘new’ rafter so it’s below the baffle and your insulation can run behind it.

Or, if it was just ‘advised’ you don’t HAVE to do it. With most new trusses, 5/8” drywall OR blocking is required on the bottom chord for horizontal support. So if your drywalling the ceiling you don’t need it.

 

[scottydosnntkno]

I don't see any trusses there,you have rafters.
Does he want you to put rafter ties in ???

Who uses 2x4's for rafters ????
WTF

The dark wood is the original truss top chord 2x4 which is extremely common size wise.

I imagine OP opened up the ceiling, cutting the webs, installed a ridge beam and sistered 2x6s or 2x8s rafters/joists to the original top chord.

So the inspector is advising the use of horizontal blocking to prevent the new rafters from twisting under load. Which if your near the span limit (17’ span on a 18’ approved span) for 2x6 for example it wouldn’t hurt.

 

[rathersmart]

Great advice! Thank you guys!

It wasn't in the build plans, but after the plan review they added solid blocking in as a requirement. So now I will be adding the blocking.

Thank you all!

 

[ssrobzoom]

Just measure the distance and stagger the blocks