Roof addition to existing CMU Wall
3

Question

Roof addition to existing CMU Wall

reverbz (Structural)

(OP)

20 Aug 24 22:17

Hey Guys,

I'm trying to add a wood roof to an existing cmu wall enclosure. The CMU wall is 8" wide and 6' tall. My initial idea was to add steel HSS columns along the top and weld a saddle to them For anchors I was going to add an epoxy anchor each side of ea. column. I've attached a sketch.

For what it's worth the roof isn't all that heavy, I can rely on the bond beam to span it between the verticals as long as I check it right? As long as it spans with the column in the middle I don't need grout directly below the posts? That was my initial thought so let me know if I'm incorrect. Do epoxy anchors seem like the best choice here or would you guys recommend a different fastener? Anything else you guys see as a potential issue with my idea?

Thank you!!

https://files.engineering.com/getfile.aspx?folder=7d6a9e46-9e46-44fe-b97f-a

DoubleStud (Structural) · Answer 1 · 2024-08-20 23:49:47

Let the numbers be your guide. You will have uplift and lateral load on these HSS. Use open building Cn from Figure 27.3-4. Your HSS will be bending to resist lateral load.

reverbz (Structural) · Answer 2 · 2024-08-21 02:14:42

@doublestud thanks for the response.

Would that just mean to check the HSS in bending and the anchors in tension from a moment couple then? I'm a little confused on that part of it.

XR250 (Structural) · Answer 3 · 2024-08-21 11:06:30

You will have a tough time making that calc out. Lot's of stability issues there.

reverbz (Structural) · Answer 4 · 2024-08-21 14:47:00

@xr250 I'm gonna go through the process and just check since it's so light I thought I could get it to work. Are you just worried about the anchors and the HSS itself checking out in bending?

DoubleStud (Structural) · Answer 5 · 2024-08-21 15:09:03

Yes light. The gravity load is not the problem. I know that will work. The wind load is what is concerning.

phamENG (Structural) · Answer 6 · 2024-08-21 15:22:04

yeah, the out of plane moment connection between the base of the HSS and the CMU will be dubious at best.

Is there a reason not to extend the wall up to roof bearing? Or do you need that open space for windows or an open air pavilion?

reverbz (Structural) · Answer 7 · 2024-08-21 15:28:35

@phameng yeah I'm a little concerned with it the whole thing seems a little finnicky. It's an open air pavilion unfortunately so can't extend the wall up. I don't have any other ideas at the moment besides adding enough columns to make the loads light and calling it a fixed connection at the base.

phamENG (Structural) · Answer 8 · 2024-08-21 15:36:36

Probably easier to put full height columns inboard of the wall.

reverbz (Structural) · Answer 9 · 2024-08-21 16:07:33

@phameng yeah that's the idea if the architect will go for it, but it's a big if at the moment. Thank you for the suggestion

phamENG (Structural) · Answer 10 · 2024-08-21 16:12:42

if they don't like the look, suggest wrapping them in 4" CMU to create false pilasters. Just make sure you detail enough room for the thing to sway inside the pilaster.

JStructsteel (Structural) · Answer 11 · 2024-08-21 17:39:12

are you using a ridge beam? Whats your horizontal reaction?

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Roof addition to existing CMU Wall
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