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Parapet Bracing for a Strip Mall 8

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vincentpa

vincentpa

Structural
Nov 9, 2005
223
I am designing a strip mall with rather high parapets. The mall is a steel framed building with steel bar joists on steel beams. The roof is a built-up roofing system. The typical parapet height is 5 feet and the parapet at the mall entrance is 10 feet. We need to brace the 10-foot parapet for sure. I haven't checked the 5-foot parapet yet. The parapet and facade is EIFS on 6-inch metal studs. We only can work with 6-inch metal studs for facade and parapets. How do you usually brace parapets on the roof? We were thinking to put metal studs at 45 degree angles and put plywood sheathing on top of the studs. The roofing would go over the sheathing to the parapet. I've noticed on some of the big box retailers that the parapet signs are braced with what appears to be steel pipe. I don't know how the connection to the studs and roof joists is made. Is there a name for this type of bracing? I thought I read of a name or a proprietary product. So the main question is, how do I brace the parapet?
 
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However you hose to do it, and the shed roof configuration is good, just remember that the best solution is to not have any exposed roof penetrations that would require pitch pockets or the ike. That's not only a maintenance headache, but a potential roof leak in the making.

Mike McCann
McCann Engineering
 
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Can you continue the vertical parapet supports down below the roof and then provide a brace on the inside of the building (below roof level).
 
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I have seen a diagonal brace back to the roof below. This was done with pipes, so that the flashing could be done similar to a plumbing vent pipe penetration, but I agree with msquared that penetrations should be avoided when possible.
 
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csd72,
Vertical support will have to be taken by a beam or a joist.

msquared48,
What are pitch pockets? The problem I see with the shed roof is that the horizontal leg will have to be 10 feet long. That is a lot of roof space on a 45 degree slope. Would you still be concerned with the pipe penetration that is flashed like strguy11 suggests? I'm concerned with this detail. The shed roof detail is easy but the 5-foot and 10-foot sloping roofs at each parapet concerns me also.
 
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Both options you present are feasible, although I prefer the shed roof option as well. With the diagonal pipe option, you would need a horizontal girt on the back side of the parapet.

DaveAtkins
 
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A "pitch pocket" is a sheet-metal or rubber boot, sometimes conical, that goes around a roof penetration such as a vent pipe and gets an elastomeric sealant....
If there were just a couple of "pipe-braces", that may be more economical. Perhaps you could stub up a vertical piece of pipe to attach the diagonal brace to. But I think I would lean toward the "shed roof" as well, since it avoids the penetrations. Could the shed just extend ~half way up the parapet (~5 feet up and 5 feet horiz.)?

A couple other thoughts:
1.) If the "shed roof" is built, ventilation of the enclosed attic may need to be considered.
2.) Don't forget to include snow drift behind the parapet.
 
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csd72,
unfortunately we cannot do that. We have to use another hanger detail to support the facade because the architect is using a ribbon window, actually a 12-foot window all the way around the building. The ceiling height is low. The parapet heights are 5 and 10 feet above the bar joists. We can only use a 6" metal stud, nothing larger. The parapet unfortunately needs to be braced.

JKW05, I have included the snow load already. This is a crazy project driven by a developer and a half-wit architect. We even have to support our foundations on helical piers. And of course we have to use moment frames with the top of steel 16'-6" AFF.
 
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vincent,

If there is a developer involved, they are mainly worried about $$.

If you have problems with the architect being difficult, you can often get around it by convincing the developer client that your way is much cheaper (but make sure it actually is).
 
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Can you cantilever the studs or provide a tube every so often and make the studs infill?
 
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We have braced high parapets numerous times in your situation with pipe braces unless it detracts from the architectural appearance. Work with the architect to determine what is acceptable.

I learned years ago not to use pitch pockets. They generally are not maintained and dry out. Use the typical pipe flashing instead.
 
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jike,
what does the connection look like between the beam/joist and pipe brace? What about the pipe to the stud wall? I would assume there is some type of whaler/girt at the top of the brace. How far apart do you usually space the braces?
 
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"half-wit architect" ...seems redundant.

Oops, I didn't say that. :)
 
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vincentpa:

The beam or joist would have a vertical pipe stub welded to it to about 18" high with a sloping plate on top with 4 bolt holes. You would then have the roofer flash to this vertical pipe. The pipe brace would then bolt to the top of the sloping plate on the pipe stub.

Be sure to check the forces into the beam or joist with wind blowing in either direction. If using joists, specify loads to manufacturer. Try to use beams or joists parallel to braces rather than perpendicular.

I have extended the building columns up into the parapet to support a girt (bracing the back of the studs) and then fasten the pipe braces to the columns. When the braces align with studs make sure they and their connections are designed to carry the vertical component.

I would definitely try to minimize the number of braces.... perhaps 10 to 16 foot spacing.

I hope this helps!

 
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If the arch. won't let me use kickers from parapet mid-height to roof structure, I usually cantilever tubes up off the perimeter beam and then brace the bottom flange of the beam back to the top chord of the joists at each brace. Might need stiffeners in the beam as well (or use a tube instead of w-shape).

j
 
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The shed roof option is the best IMO. What we typically do is provide kicker braces back to the flat portion of the roof and sheet it. The roofing is then placed on the sheeting with NO penetrations. Remember, you won't need to take the kicker braces up to the top of the parapet, usually we go ~2/3 of the way up, let the top 1/3 cantilever.
 
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I agree with Einstein.

Sorry I couldn't get back on the pitch pocket definition - I was out all day.

Mike McCann
McCann Engineering
 
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