Residential Elevated garage on wood framed walls 1

[BndStructural]

Hello,
I have received a project of a high-end custom home on a sloped lot. The slope is steep downwards from the right of way. The driveway will be used as a bridge to the garage and main level of the home. Finished space will exist under the garage that will be used for storage. I have worked on many elevated garages built directly on the concrete foundation walls, but never another story above or on wood framed walls. The home designer has asked me to come up with the design and has provided no input. I typically would lean towards steel wide flange beams and a one-way slab resting on the stem walls with a sloped bearing pad. Do I still use wide flange beams and a one-way slab, but instead bear on a wood wall? Do I to tell the designer that wood walls are not a good idea? I see wood floor framing used all the time. but I myself have stayed away from it. To add, the owner intends to install a car lift in one corner to be used to store one car in the air on the lift and another underneath that car. What design concerns should I consider here?

 

[BndStructural]

The contractor surprised me as most residential contactors want as little use of steel as possible. He comes from a commercial background so I guess that's why he's comfortable with steel. I think I may have a solution that works well to tie the two systems together. If I run a steel angle ledger on the balloon framed wall lag bolted to blocking and attach the steel decking to the ledger with tek screws I should theoretically be able to transfer diaphragm forces into the wood shearwalls. This would also create bracing for the balloon framed walls. Should I have any hesitation with this design?

 

[SWComposites]

Differential settlement?
Thermal expansion difference between the wood, concrete and steel components? (the areas might all be at different temperatures)

 

[ALK2415]

Can you alter the steel frame [columns] to be inclined ? to make your structure much more stable and reduce the bracing elements as much as possible.

 

[BndStructural]

Can you alter the steel frame [columns] to be inclined ? to make your structure much more stable and reduce the bracing elements as much as possible.

This is not desirable since the space below the garage will be used for storage and they would like to have the columns as close to the perimeter as possible to maximize useable space.

 

[XR250]

Can you alter the steel frame [columns] to be inclined

How does that make it more stable?

 

[BndStructural]

I have been working through this to come up with a suitable beam and column layout. The garage shape not being symmetrical in nature makes this a bit more difficult. With a 6.5' max span between beams I have come up with a one-way slab design using a 6" thick slab. The slab is aided with the use of 18ga non composite metal decking, although the slab is designed without the decking. I have a couple of unsupported areas that I have not been able to come up with a solution along walls. I am using steel angle ledgers along the wood walls the long direction of the garage, but do not feel comfortable picking up the slab loads at these other locations using an angle ledger (see highlighted areas). Beams and posts are positioned in a way to have some consistency in spacing and maximize the useable space/ not block doors or hallways. Any ideas how to support these areas?

 

[XR250]

If I run a steel angle ledger on the balloon framed wall lag bolted to blocking and attach the steel decking to the ledger with tek screws I should theoretically be able to transfer diaphragm forces into the wood shearwalls. This would also create bracing for the balloon framed walls. Should I have any hesitation with this design?

Might want to consider shrinkage in the wood frame over two stories versus none in the steel frame. This could cause an issue with the hybrid approach.

 

[BndStructural]

Might want to consider shrinkage in the wood frame over two stories versus none in the steel frame. This could cause an issue with the hybrid approach.

This is certainly a valid concern and goes back to my hesitancy of using two different structural systems of different materials. I keep coming back to disliking the entire design. The homes designer was surprised when I sent him this layout as he thought there would be less beams and posts. I get a feeling these guys don't understand the complexities of what they have designed architecturally (what's new).

 

[jayrod12]

I truly don't understand the resistance to concrete walls from foundation to underside of garage. It is so common in this area that I wouldn't of even entertained another solution. Where I am, the high end houses use hollowcore with a topping slab and traffic membrane for garages over basements. The hollowcore bears directly on concrete walls and/or steel beams.

 

[BndStructural]

I truly don't understand the resistance to concrete walls from foundation to underside of garage. It is so common in this area that I wouldn't of even entertained another solution. Where I am, the high end houses use hollowcore with a topping slab and traffic membrane for garages over basements. The hollowcore bears directly on concrete walls and/or steel beams.

It's purely a limitation of the GC.

 

[XR250]

This seems like a really bad idea... Garage slab on i-joists...

https://lsc-pagepro.mydigitalpublication.com/publication/?m=23705&i=811009&p=32&ver=html5

This is my favorite part...