Engineering Question-Widows Walk

[winterdd]

Hey guys, just looking for some opinions. Any structural engineers here in the forum that could suggest a way this would be done structurally? It's a first for me and the client wanted it and also wanted it allow light inside the home. I am very curious how the opening in the vaulted ceiling planes would work. What would what the "tunnel" going thru the attic rest on? Very curious if this is even possible.

 

 

[CharlesVolz]

Howdy Rob,

 

I would use horizontal exposed structural beams across the opening and horizontal ceiling planes before and beyond. (If customer would let me,)

 

I would like the look and feel much better.

 

Best,

Charles

[Doug_N]

The big problem is the outwards pressure from the cathedral ceiling followed by a lack of support under the roof support wall.  

 

The cupola prevents a continuous ridge beam, but there are ways (very expensive ways) to do this with structural steel with moment bracing.  I agree with Charles as a more practical approach.  This would depend on the depth of the pockets of the owner.

[winterdd]

I agree, of course around here I send my plans of to be engineer stamped but I still try to avoid sending anything that is not able to be built or too complex.

[plannedRITE]

Not a perfect example, as it continues to the end walls, but I imagine that it would likely be similar. Though this builder is working on a different one of our projects, this isn't one of ours so I don't have details that I can share. 

https://www.instagram.com/reel/Cn4cUHorowQ/

 

I'm interested to see how you detail it out, share updates!

[CAmichael240114]

In these type of cases I use steel portal frames with concrete base footings

[VHampton]

Flitch plates bolted inside micro-lams can address the roof.

 

They can weld a moment connect at the ridge. They'll do the same welds at the base of the longer walls. 

 

The rafters by the Kitchen have no bearing wall.  They'll need a W section to handle the gravity loads (posted on both ends).

 

There's enough height however to get a tall beam in there. 

 

Engineer will probably size something 14 inches tall and at least 100 lbs per foot. 

 

By the way, even if the vaulted area gets collar tied (which it should) steel over the bar stools is a must have. 

 

 

 

[winterdd]

2 hours ago, VHampton said:

Flitch plates bolted inside micro-lams can address the roof.

 

They can weld a moment connect at the ridge. They'll do the same welds at the base of the longer walls. 

 

The rafters by the Kitchen have no bearing wall.  They'll need a W section to handle the gravity loads (posted on both ends).

 

There's enough height however to get a tall beam in there. 

 

Engineer will probably size something 14 inches tall and at least 100 lbs per foot. 

 

By the way, even if the vaulted area gets collar tied (which it should) steel over the bar stools is a must have. 

 

 

 

That's some good info right there. Something tells me you are an engineer.

[Michael_Gia]

I’m no engineer but have done similar before. 
 

Trusses like the one in my crappy marked up drawing are doubled up on either side of the lookout shaft/steeple. Between those doubled up trusses are lvl’s to close the box. 
 

[VHampton]

20 hours ago, winterdd said:

That's some good info right there. Something tells me you are an engineer.

 

Architect w/ civil engineering background, but don't take my post as anything other than general observations. Your design is do-able in any number of ways, and ultimately the engineer will decide. 

 

For example... They could opt to use a four sided ridge at the base of the oversized cupola. This would allow the upper "cupola" walls to bear down onto the 4 rectangular interlocking ridge beams which would spread the load onto the structural hips.

 

Very much like Michael has shown, and as others have suggested. The use of collar ties as shown in Michael's cross section would help support the ridge by means of posts.  

 

The bottom line is that there are always many ways to approach a structural solution. If truss manufacturing is local to your area, then by all means consider that as a possible cost savings method. 

 

All the best! 

 

 

 

 

[winterdd]

2 hours ago, VHampton said:

 

Architect w/ civil engineering background, but don't take my post as anything other than general observations. Your design is do-able in any number of ways, and ultimately the engineer will decide. 

 

For example... They could opt to use a four sided ridge at the base of the oversized cupola. This would allow the upper "cupola" walls to bear down onto the 4 rectangular interlocking ridge beams which would spread the load onto the structural hips.

 

Very much like Michael has shown, and as others have suggested. The use of collar ties as shown in Michael's cross section would help support the ridge by means of posts.  

 

The bottom line is that there are always many ways to approach a structural solution. If truss manufacturing is local to your area, then by all means consider that as a possible cost savings method. 

 

All the best! 

 

 

 

 

What a perfect example of a pic.

[RL-inc]

Quite possibly the worst attempt in history at an ISO scribble on a screenshot but here is my 2 cents.

 

To piggyback on the truss concept, if you could use scissor or parallel chord trusses similar to what Michale and V are mentioning above, you could look at a multi-ply girder on either end and box girders running in-between.

 

Truss company should be able to manufacture a profile for the girders that will allow for a deep enough box to hang off of it as long as you are willing to provide sufficient depth.

They may be able to design them with enough drag load to handle the lateral requirements.

 

 

[VHampton]

1 hour ago, winterdd said:

What a perfect example of a pic.

 

Indeed. It's quite similar.  That's the (4) sided flitch plate ridge beam which carries the cupola. 

 

They furred-out the load bearing cupola walls with an interior thickness. 

 

This is probably what your engineer will do.  Meaning to place the cupola over the structural ridges.

Then you can frame down the shaft much lower as per your rendering (just as they did in the photo). 

 

Trusses will also eliminate the need for the steel over the bar stools. There will still be a beam, but now there's only "dummy" rafters (sloped interior ceiling framing) which will not be presenting tons of weight. (A glue-lam could probably do all of the work in carrying the sloped ceiling).  

 

Good luck with the project!