Concrete deck

[JStructsteel]

Starting some prelim design on an elevated concrete deck in the back of a walk out basement. Contractor thinks it should be separate from house and total independent structure, perhaps they than footings

I agree, but was thinking of threshold at doors….just have a gap and caulked?

It will be enclosed but not whether tite. No architect involved so trying to advise contractor as best I can.

 

[KootK]

- How big is the deck relative to the house? A basic plan would be helpful.

- Concrete basement walls or block?

For some situations, I'd favor tying the two structures together given that I see the biggest, real world risks here being:

1) Differential settlement and;

2) Water getting the joint between structures unless you intentionally mean for that to be a drainage path.

 

[JStructsteel]

KootK, Attached is plan for covered porch/deck.

Basement below is walkout, so framing is wood/brick.

I see the brick being an issue. Pour stop at the brick?

Differential settlement and lateral movement would be my biggest issue.



[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1677002923/tips/Covered_Porch_dkbizc.pdf[/url]

 

[KootK]

Thanks. With the wood + brick existing, the independent structure does sound like the way to go.

Basement below is walkout, so framing is wood/brick.

"Walkout" means different things in different places. Many places it means wood. Some it just means concrete with a door.

What have you got in mind for a drainage strategy for any water that lands on the roof of this thing or makes its way to the floor?

An elevation would also be helpful if you're feeling generous.

 

[JStructsteel]

KootK

Here is a rear elevation. You can see the porch is all glassed in. To complicate more, the roof is coming over and the outside of the porch is load bearing.

Perhaps the walkout being concrete allows for me to have a place to tie in my slab, beam bearings.

We talked about water getting in, with the windows my thoughts are a flat slab. Its more that its part of the house than a outside deck/porch. Just not a conditioned space.

Thoughts?
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1677076259/tips/rear_elev_ykcvwv.pdf[/url]

 

[KootK]

To complicate more, the roof is coming over and the outside of the porch is load bearing.

Thanks for the elevation. This was just what I was worried about. I'd have to think that, from an envelope perspective, the roof of the existing building will be made contiguous with the roof of the porch. And that pretty much implies that the roof will be structurally contiguous from the existing building to the porch. And if the roof is to be structurally contiguous, surely it makes sense for the floor to also be structurally contiguous. So I vote for tying things together. I feel as though the addition is something that you could do successfully in wood which might make it a bit easier to accomplish the tying together.

 

[EdStainless]

Around here if it fastens to the house, it is house.
My neighbor has a walk out basement and wanted to do something similar.
He would have to take the new footings to the same depth as the existing and tie it all together.
With 9' basement, 4' frost depth, and then footings that meant some seriously deep holes.
He built it detached but very close.

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P.E. Metallurgy, consulting work welcomed

 

[dik]

I'd likely separate them... Concrete is a heavy dead load issue and will possibly add to differential settlement. The wall elevation has a bunch of openings in the masonry 'veneer?' This would be prone to cracking. My $.03 (used to be $.02, but due to inflation).

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

-Dik

 

[JStructsteel]

Thanks all
This is a new build all around.

I’m going to suggest the basement walls come up to the top of patio, beams supported on the walls. Plus I can use the wall for stability

I have been asked to design all the footings too at this location.

 

[KootK]

Oh... I just assumed that it was an addition because we were discussion potential separation. For a new build, I would absolutely tie things together somehow.

If you're committed to CIP concrete, a nice system might be intermittent beams perpendicular to your CIP basement wall and a thin, one way slab run over top of those.

 

[JStructsteel]

Thanks
My thoughts are steel with composite deck or form deck

 

[jayrod12]

I would not be doing composite or form deck for an exterior elevated deck. Even the higher galvanized versions are going to corrode in time.

If the building is mostly wood, I'd rather be doing it out of wood as KootK alludes to. But if your sold on concrete, cast-in-place is really the only option without metal deck.

 

[JStructsteel]

Good point on composite deck.

Owner wants steel and concrete

Form deck would be ok, it’s not part of slab capacity, but will be a maintenance item.

 

[jayrod12]

I'd probably just do it all CIP then. Less maintenance than even hot-dipped galvanized steel beams with a concrete slab.