• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Rafter thrust control for flush beam

4thorns said:
Who is responsible for determining this information and the required connection? Is this something you would determine and inform the builder?
It is the builder's responsibility to provide this information and our job to check it. We are not designers.
 
"It is the builder's responsibility to provide this information and our job to check it. We are not designers."

Agree.........
 
OK. Let's say that the builder has provided you with all the info and has chosen a strap that he feels is adequate.

Would you be willing to explain to me how you would prescriptively determine whether or

not his fix is acceptable?
 
By the manufacturer's rating of the strap and the information that he provides. There are plenty of easy calculations that can be performed to verify this. In addition, through conversations with structural engineers in the past, we have an idea what works in our area(snow load may vary) based on the size of the roof and the direct comparison to the nailing requirement VS the specifications of the strap from the manufacturer.

We can always tell them to go to a PE and get the non-prescriptive fix specified. Please don't forget that not everything is in the IRC and we are sent to the IBC and NDS which has much of this information prescriptively.
 
4thorns said:
OK. Let's say that the builder has provided you with all the info and has chosen a strap that he feels is adequate. Would you be willing to explain to me how you would prescriptively determine whether or

not his fix is acceptable?
It is called flying by the seat of your pants.
 
jar546 said:
It is the builder's responsibility to provide this information and our job to check it. We are not designers.
You could offer guidance, everyone needs to learn.
 
Simply provide equivalent to table R802.5.1(9) footnote e.
 
MASSDRIVER said:
Beam is probably larger than the joist, you just can't see it from the camera angle. doubt seriously you can strap on top.Great minds and all... :)

Brent.
couldn't they use something like a simpson VB brace over the top? I have not seen it done or looked much into it, but have seen it in the catalog and seemed reasonable.......
 
steveray said:
couldn't they use something like a simpson VB brace over the top? I have not seen it done or looked much into it, but have seen it in the catalog and seemed reasonable.......
That was my thought............

VB Knee Braces
 
I just read the catalog page again and the VB brace requires the members being connected to be a minimum of 2-1/2" so that's out if those are 2x joists; strapping on the bottom and blocking to pick up where the gyp. bd. can't be nailed as suggested above would be quick, good, and easy.
 
DTT2Z%20Inst%20Deck%20to%20House.jpg


Would make the drywall guy happy. Probably only needed every 2nd or 3rd rafter
 
The main problem with the VB brace is that when thrust is applied it would tend to lift the joists as they seperate from the beam unless there were something like a ledger or upside down hanger above the joists to keep the joists from rising. Used as simpson specifies the hanger is in the correct orientation for the load to pull the joist down into the hanger.
 
"Don't let Glenn see that. His eyes will burn and catch on fire. :wink:"

For sure.................
 
I would build it with rafter ties like Mark said in post #13 that's old school.
Have to agree in this case. You have existing joist hangers. Lay another piece of steel over them and now you have a huge bump

in the ceiling that you will never hide without a lot of work by guys that may be P@#$ed off!

I noticed that the ceiling joists don't line up from one side of the main girder to the other. Strange. Rafters appear to line up at the ridge.

The main problem with the VB brace is that when thrust is applied it would tend to lift the joists as they seperate from the beam unless there were something like a ledger or upside down hanger above the joists to keep the joists from rising.

Used as simpson specifies the hanger is in the correct orientation for the load to pull the joist down into the hanger.
Is it possible to prescriptively determine whether or not the fasteners in the hangers are adequate to resist the uplift created by

Knee Braces?
 
4thorns said:
Is it possible to prescriptively determine whether or not the fasteners in the hangers are adequate to resist the uplift created by

Knee Braces?
Most joist hangars are rated for uplift in pounds. Uplift is not the issue, however.
 
I agree that uplift is not an issue as it sits. I was referring to DRP's post:

The main problem with the VB brace is that when thrust is applied it would tend to lift the joists as they separate from the beam unless there were something like a ledger or upside down hanger above the joists to keep the joists from rising. Used as simpson specifies

the hanger is in the correct orientation for the load to pull the joist down into the hanger.
If the uplift created by the Simpson Knee Brace can be restrained by the existing ceiling joist hanger fasteners then this detail is a viable option.

If not, a ledger above the joist could be installed (per DRP) above the joists. A little more work for the guy swinging a hammer as

opposed to a lot more work for the hanging the rock. In the end it should come down to a satisfied home owner. You're gettin paid either way.
 
Top