Porch connections to walls
Porch connections to walls
(OP)
I recently ran into a design that requires me to connect a wrap around porch to a wall. The architect wants a wrap around porch and part of the wall the porch wraps around has 2-story full height studs.
Per the code, I'm supposed to have an out-of-plane lateral connection to the wall. That's easy when connecting to a rim board or concrete wall. With this situation, I am using an angle for attachment as all I have are wall studs. Anyone have any better more cost effective ideas? I haven't ran the calc on the angle yet, this is just what I'm thinking of doing.
Also, where in the code does it say what you are supposed to use for an out-of-plane load for wood to wood deck connections? Concrete is an easy straight forward 200 plf...does the same apply for wood in this situation?
Per the code, I'm supposed to have an out-of-plane lateral connection to the wall. That's easy when connecting to a rim board or concrete wall. With this situation, I am using an angle for attachment as all I have are wall studs. Anyone have any better more cost effective ideas? I haven't ran the calc on the angle yet, this is just what I'm thinking of doing.
Also, where in the code does it say what you are supposed to use for an out-of-plane load for wood to wood deck connections? Concrete is an easy straight forward 200 plf...does the same apply for wood in this situation?






RE: Porch connections to walls
RE: Porch connections to walls
It is a lot of connection. The deck screws are for in-plane shear to transfer into the ledger and from the ledger to the blocking, the lag bolts for vertical, and the angles are for out-of-plane loads. The way I interpret the 2012 IBC "Section 1604.8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal." is that you have to have connection for both planes of shear...in and out of plane...similar to what you would do if connecting a ledger to a concrete or cmu wall...thus the angles @ 48" o.c. to positively anchor the porch to the house.
Could I use the lag bolts to take care of the out-of-plane loads? Yes. But, in order to do that I would have to put the ledger in a Cross-Grain bending application which all literature I have (and my previous mentors) says to avoid this.
RE: Porch connections to walls
RE: Porch connections to walls
RE: Porch connections to walls
RE: Porch connections to walls
I may be misunderstanding this issue, and if so, I apologize.
RE: Porch connections to walls
The IRC R502.2.2.3 requires two hold-down devices (one each end of deck) with a design capacity of 1500 lbs, horizontally anchored. So 3000 lbs per deck.
For decks we use Simpson DTT2Z deck tie, one at each end. In your case the DTT2Z are too long for 2X6 studs. You angle solution seems sufficient, I would probably double the studs at the angle location.
The out-of plane force for structural walls is defined in ASCE 12.11.1 as 0.4*Sds*I*W or 0.10*W.
RE: Porch connections to walls
As for loading usually you have wind and seismic or some use a person/activity lateral force which I won't get into. You then get your Tension=Compression = M/d. As for seismic I have seen an interesting approach where you actually calculate the seismic force for the building then use a simple F=ma to see what force the deck 'sees'. Basically your derive the EQ force on the building at the level of the floor the deck is at. Then knowing the floors mass, solve for acceleration. Then apply this acceleration to the deck x deck mass = EQ force on deck.
As for cross-grain bending I'm not sure what you would use for an allowable bending stress. This really is not weak-axis bending this is - looking at a cross section say 2x10 the 10" being vertical dimension you clamp/fix the bottom then apply a lateral (left/right) force to the top. Unless I'm misunderstanding.
EIT
www.HowToEngineer.com
RE: Porch connections to walls
As for Cross-Grain bending...I attached a page out of Breyer's text book. The same concept applies to what I'm doing, the only difference is that his example shows a concrete wall and mine is a wood wall. The only way to get any out of plane force for my situation into the wall is via an angle (or at least I think so) so that you avoid cross-grain bending.
It's easy when attaching to a floor system.
Maybe I'm wrong and completely over analyzing this scenario?
RE: Porch connections to walls
http://www.fairfaxcounty.gov/dpwes/publications/de...
RE: Porch connections to walls
RE: Porch connections to walls
If yes - I'm not aware of one except for the minimum created by Wind/EQ (or once again created by moving people).
What's the difference?
EIT
www.HowToEngineer.com
RE: Porch connections to walls
It then progressed to discussions about "Out-of-Plane" minimum loading requirements...which I still don't have an answer to so I will base it off of weights of materials and ASCE-7 12.11.1
RE: Porch connections to walls
What would you be using for you're minimum if it were attached to the floor? Why are you treating this differently? Maybe I am missing something...
EIT
www.HowToEngineer.com
RE: Porch connections to walls
In the past, I have used weights of materials for seismic calcs as there is little to no wind for out-of-plane loading...I was just kind of curious if there is some "Minimum" out-of-plane standard to use as I haven't seen or heard of anything in the code.
I do have some disagreement with the IRC (and its language) though and it's suggested use of the hold-down tension ties. When your decks get long, you have to add more tension ties to meet your diaphragm length to width ratios and it doesn't necessarily say that in the code...at least if you are treating your deck as a true diaphragm.
RE: Porch connections to walls
EIT
www.HowToEngineer.com