Wood Parapet Detail with Straps only

[JKJohn]

Hi everyone, thanks for reading.

I am working on a residential project with a flat roof and a wood deck on top of it. One side of the deck has a parapet that also serves as rail to the deck. Balloon framing is an option but with a high ceiling and a few feet of space between the deck and the roof, the stud length is becoming too long.
Both the deck framing and roof framing are 2x10@16”O.C.
Does the attached detail work? I am only using two straps, one on the outside face and one on the inside face of the studs.
It works on my paper and I found no issues with it. I just want to see what you guys think of it since I have not seen it before.

The detail is attached.

Thanks again

 

[driftLimiter]

What happens when the straps are put on tight enough or what happens as they deflect? Not a fan of this detail. I would try to get a continuous post spaced maybe 48" o.c. then use the double top plate to span between them. The cont. would be strapped back into the diaphragm to get the shear reaction at the top.

 

[phamENG]

Hard pass on that one. Even if they put them on tight, what happens when the wood finishes drying and shrinks?

 

[JStructsteel]

I agree with drift. From the top plate at the ceiling, cantilever some posts up above the deck and then span horizontally.

Or, just cantilever every stud from the ceiling. So stud to ceiling top plate, then studs from top plate to top of rail.

 

[JKJohn]

Wouldn't the argument of straps not installed tight or wood shrinking be the same for shearwalls strapping? We use metal straps all the time.

 

[phamENG]

We do. I've also seen lawsuits over shear wall straps installed incorrectly.

Nail slip in a shear wall strap is accounted for in the deflection equation. Try applying it to your wall and you'll get an idea of how far it'll move. It won't be pretty.

 

[SJBombero]

Have you looked at using threaded rods with a 2x6 or 2x8 parapet to restrain the overturning? I've been able to make that work before.

 

[dik]

I'm not big on wood, but this is what I did for a Church about 3 years back...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[JKJohn]

Dik - In principle this is the same concept I have provided. Two straps one on each face.

phamENG - The nail slip in shearwalls is mainly due to plywood nailing. The nail slip formula is (v*h)/(1000*Ga). Ga is a product of plywood. Is there another way to calculate the nail slip?

SJBombero - How would you attach the rod to the studs? Would you use a hold down bracket?

JStructsteel and driftLimiter - I like the idea. Extra water proofing around the deck joists connection to the vertical studs. Will have to run it by the architect

 

[manstrom]

I think your detail works on paper, but may be a little wiggly in practice. The straps will have some sack in them. Probably ok for a parapet, but not for a railing.

Another option is to nail the parapet studs to the side of the 2x10s. L shape.

 

[kipfoot]

I'll join the dislike your detail chorus. How about something like this:

 

[HouseBoy]

I like kipfoot's idea as it provides some stability to the deck platform.
Still, I would want more "positive" horizontal anchorage of the rail posts (near the top of the deck joists). Maybe a 4x6 every 4 ft that would be anchored to the deck joist with a Simpson DTT2Z using a 1/2" bolt thru the 4x6.

I wonder how much slope the roof deck will have (and how that will affect the available space for the diagonal brace).
Also wonder about flashing the whole thing....

 

[SJBombero]

This is generally what I have done.

https://files.engineering.com/getfile.aspx?folder=ee310ba1-3e78-468c-99cd-7dbf5ce70fef&file=

[Untitled]_2022111707582117.pdf

 

[dik]

My detail worked fine, and was not a parapet; it was designed as a guard. It was constructed as designed and is a solid as a rock.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Brad805]

I have used the connectors below for short walls needed for roofing or below windows, but not as a railing. This is a railing. Comparing the use of the straps to a shear wall does not track for me. People will stand up against the railing and lean against it. The wall will not perform well long term. I too prefer kipfoots detail.

 

[DoubleStud]

Frame multi pack studs between rafters and do some kind of a fixed connection with blocking. Framers do this all the time to install posts for handrails. Same concept can be done. Or maybe something like this.

https://seblog.strongtie.com/2015/10/deck-guardrail-update/

https://www.youtube.com/watch?v=lTRquLcL6Jo