Guardrail on Brick Masonry Parapet - Connection 1

[bookowski]

Brick masonry parapet that extends 16" above the roof line, with a 26" tall steel guardrail sitting on top of the brick parapet. I have come across this in different configurations. The one that I am looking at now is a two wythe wall with an enlarged grout space between the two wythes and #3 vertical bars in there. The brick parapet section is already built, and now the architect wants to connect the steel rail to the top (would have been nice if I was asked to look at it before they built the parapet...).

I've seen similar rails but have never detailed one. Does anyone have any suggestions? The overall parapet width is 10" (2 wythes with enlarged grout bed between). Adhesive anchors will have minimal edge distance. The posts are at 2'-6" which is the only helpful part.

What is a typical detail for this situation?

 

[dhengr]

Ask the Arch. to show you his code compliant perty pitcher of how he imagined this guardrail would be fixed to the top of the parapet. And, you will tell him if it will work or not, and if he has to go back to the drawing board, or his CAD screen, with your suggestions. Sometimes when they make a mess, they ought to have to step in it, and then clean their own shoes off.

 

[Bagman2524]

Contact Hilti and see if they have any suggestions. Their guide provides for attaching to CMU but I don't know if they anchors can be used on brick or not. Since your rail height is only 2'-6, base moments will be lower than normal and perhaps anchoring to brick parapet will work. I've also had a case where architect showed underdesigned rails and we had to redo the design.

 

[XR250]

Core holes between the wythes and grout the posts in????

 

[bookowski]

yeah I was wondering about the core and grout option... I can't decide if that's going to make it worse or better.

The posts are closely spaced, so 200# controls, and at 26" tall to the brick the anchor forces are relatively low. I also am accounting for load sharing since the posts are at 2'-4" o.c. I think it will probably be ok - just tough to show it. Hilti won't stand by anchors with such little edge distance to brick.

The 2nd question is what is the proper detail for this? Should the short brick parapet be reinforced and grout the posts in? There would not be much resistance to popping the face off the brick with a grouted post.

Attached is photo - there is supposed to be rebar extending from the CMU wall into the parapet. That's what is on the arch. detail, I didn't see it being constructed though. It looks pretty well built from what I saw, and the contractor is competent.

 

[SteveGregory]

Forget about steel posts.

How about reinforced brick piers (2 wythes x 24")instead of steel posts with 24" clear to the next pier. The grout space should allow you to drill deep enough holes (18"-24") to sink some rebar and adhesive. Then cap the piers with precast (guardrail) and anchor them down.

The architect can have fun detailing the space between the piers!

 

[SAIL3]

I would use a 3" wide U-shaped steel strap that would extend down each side of the parapet, a required length and use HILTY anchor bolts to connect the strap to the sides of the parapet, preferably located as close to the #3 rebar as posible...the H/R posts woud be weled to the strap..

 

[concretemasonry]

Borowski -

That wall is a grouted three wythe masonry wall with grout placed in center.

A good structural engineer with a knowledge of masonry would realize that you have a 10" bonded masonry wall (16" high) with the steel in the center.

To many people think you have 3 individual layers rather than a solid bonded structural masonry wall section. It is not a 2" "concrete" wall with edge difference of the grout and does not realize the wall is a 10" masonry wall with the high slump grout filling the void between the brick and the excess water and cement is drawn into the masonry units during construction process. It is a structurally bonded masonry wall that also has reinforcement in the center according to masonry codes. Hilti must have someone that can recognize the actual wall construction (and real edge distance) and the application. They may want a slightly longer product if they do not have enough depth to distribute the loads or they wear both a belt and suspenders, but they may run into an extra horizontal bar in the top portion of the wall.

With a 26" railing height and anchored to 16" thigh 10" thick masonry wall every 24", there should no problem with the parapet. I know of a 12 story apartment building (built under code min 1965) that consisted of a wall section with 4" brick, 4" masonry grout and a 4" brick that has been and is a great structure.

Obviously, the architect and owner will not appreciate a structural steel cap over the wall for appearance and cost purposes when a common parapet cover with proper lips and sealing would perform better.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Ron]

Assuming the grout space is at least twice the width of the post, the better option is core the holes and grout the posts in.