Basement room below garage

[TopagnaOverlook]

This is a new construction project.  Due to lot size constraints, I'd like to put a home theater in the basement underneath a 20x20 2-car garage.

Structural engineering needed for the "ceiling" weight capacity, and waterproofing.

I don't know how to approach this with Chief.

 

 

 

 

 

[Doug_N]

Do a model of the house in Chief Architect and make a basement under the garage.  The garage floor will be a suspended slab, probably with at least one steel drop beam under the slab.  The ends of the beam can bear upon the foundation stem wall or on pilasters.  More than likely you will need one column in the center of the beam if the garage is a double width.

 

The beam will probably be 8" deep so make sure that you have enough headroom (say 7') under the beams, and then make drawings for the structural engineer.  He(she) will tell you how to change the drawing to suit, and provide a structural drawing along with load calculations.

[TopagnaOverlook]

 Thanks Doug!  I'll go down that path.

[rlackore]

Another solution is to use precast concrete planks, which can easily span 20' without intermediate support.

[Doug_N]

16 hours ago, rlackore said:

Another solution is to use precast concrete planks, which can easily span 20' without intermediate support.

I don't know about your jurisdiction, but that solution for a garage would require engineering to prevent possible fluid leaks from entering the habitable space.  The plans examiner would still require the certification of the design for the building assembly, not just for the pre-engineering slabs.

[rlackore]

29 minutes ago, Doug_N said:

I don't know about your jurisdiction, but that solution for a garage would require engineering to prevent possible fluid leaks from entering the habitable space.  The plans examiner would still require the certification of the design for the building assembly, not just for the pre-engineering slabs.

 

We do plank garage floors all the time. Careful detailing is required, of course, but nothing out of the ordinary - you certainly don't need an engineer to design a waterproof deck. Typically we use a split slab design, much like a plaza deck or protected membrane roof (plank-barrier-insulation-wear layer), so the space below stays warm and dry. Plank manufacturers provide load tables, so it's no big deal to select a size, series, etc. to run your loads for the foundation design. The biggest PITA is ensuring the plank-to-foundation connection is able to transfer lateral loads imposed by adjacent horizontal diaphragms - plank manufacturers don't like to touch that topic, and there is scant testing and research to rely on. You'll need to provide the plank manufacturer with a good drawing that indicates openings, uniform loads, and point loads - their engineers will do the rest. And, of course, review the shop drawings!

[GeneDavis]

Here you go.  Great information here.  http://www.enconunited.com/wp-content/uploads/2017/07/HCM002-Hollow-core-Residential-Design-Manual-Complete-3.23.15.pdf

[lbuttery]

as stated there are fumes issues and fire issues

 

check with your local permit office for their code requirements 

 

I was working on an office above a garage and the permit requirements were so stringent and costly

the client abandoned the project

 

Lew