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StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7076
Experience:  Structural Engineer
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Need some assistance designing reinforcement and size of

Customer Question

Need some assistance designing reinforcement and size of basement walls and footings for single story residential addition.
Submitted: 8 months ago.
Category: Structural Engineering
Expert:  StructuralEng replied 8 months ago.
Expert:  StructuralEng replied 8 months ago.
I can help
Customer: replied 8 months ago.
Great. The addition is 18'x26' with a full basement, one story wood frame above, 4:12 pitch roof.
Customer: replied 8 months ago.
The grade slopes along the 26' side from about 7' backfill to floor level at the back. So the north 18' long wall supports about 7' backfill along the entire length. The south 18' long wall has no backfill. And the 26' wall supports 7' backfill at the front and slopes gradually to none. The other 26' wall connects to the existing house. Does that make sense?
Customer: replied 8 months ago.
We do not have a soils report, but typical soils in this area are about 2000 psf.
Customer: replied 8 months ago.
This locale uses the 2012 IRC. The basement foundation walls will be CMU. I'd like some assistance sizing the footings and designing the CMU walls. This is what I came up with, but I have no idea if it is right. 18' retaining wall: 12" fully grouted CMU with #5 @ 32" O.C, on a 32"x12" continuous footer w/ 3 #5 bars and vertical ties into wall @ 32" O.C. I would imagine the other two walls could be lighter. Let me know if I can provide more information. Thanks for your help.
Expert:  StructuralEng replied 8 months ago.
Do you have drawings and design loads?
Customer: replied 8 months ago.
I have basic floorplans. The floor above has a live load of 40 psf, dead load of 20 psf, the roof snow load is 20 psf. For the foundation loads, I was starting with the IRC and typical soils. Let me see if I can upload the plans.
Customer: replied 8 months ago.
There will be a 4" lally column in the center of the basement, with a LVL girder running the 18' dimension. 2x8 joists @ 12" O.C. will run the 26' dimension and bear on the LVL girder for an effective span of about 12'.
Customer: replied 8 months ago.
Any update?
Expert:  StructuralEng replied 8 months ago.

Is it a single floor only?

Customer: replied 8 months ago.
single story 2x4 wood frame
Customer: replied 8 months ago.
Vinyl siding
Expert:  StructuralEng replied 8 months ago.

You can use 24" wide footings.

Expert:  StructuralEng replied 8 months ago.

18' is a very tall retaining wall. Is that correct? It's tied into the foundation and first floor, correct?

Customer: replied 8 months ago.
It is tied to first floor, 18ft wide, 8'8 tall (13 courses
Customer: replied 8 months ago.
The "retaining" wall is the basement wall that will be buried, holding back all of the fill. The other basement walls will not be fully buried. I think it's called a daylight basement?
Expert:  StructuralEng replied 8 months ago.

12" block is more robust than it needs to be, but will certainly do the job.

Customer: replied 7 months ago.
5 bar @ 32" O.C. along the wall is overkill? Should I go to 48" O.C, #4 bar?

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