suspended slab vs. hollowcore for residential drive

[gopherwood]

I am designing a slab for a suspended garage and suspended drive/parking area for a custom home I am building.

Here is what the details are. The garage span is 24. Length is about 38 feet (3-car garage). The parking area is about 40 feet deep and is split into two spans 16' and 24'. Parking area is also about 38' long. I am using 160 psf live plus dead load and am planning on using 2" metal decking with underneath girders 6' on center (5 " slab). I am confident in my girder and decking calcs; however, is 160 psf low, medium or heavy?

Also, I am only vaguely familiar with hollowcore. Does it offer a lot of advantages?

Thank you! I am a new visitor to this website from South Carolina.

 

[JAE]

Parking garage live load capacity in most all building codes (and ASCE 7) is 50 psf.

 

[jaspax]

Hi guys...
I have a similar question. I am building a custom plan as well with a suspended 3 car garage. The design of my home has a small kitchen pantry (4ft x 8ft) that would poke out into the garage. My builder is telling me we can't build on a suspended slab, but has no technical reason other than you just can't.
What do you guys think?
Thanks,
Jason

 

[JAE]

Ask him why not...as long as it is stiff enough, and as long as it is strong enough - why not....

Also - may have thermal issues (insulation) but that can be detailed properly to control.

 

[jddoe]

Using 50psf live load for a residential garage would be considered light by most designers involved in providing commercial products for residential construction. It is true that cars parked bumper to bumper, door handle to door handle will not approach 50psf (more like 37psf), but you never know what kind of storage facility a residential garage may become. In our office we use 125psf live load.

 

[astructurale]

Hollowcore installation is quick and easy, and they may be topped or untopped. For these size projects the slab would be finished in just one days work. You most certaintly can build on a suspended slab. It is done all of the time. As JAE said you may need to add some insulation.

As for the loading 160psf does seem high. 50psf is correct for garages, but many do use garages for storage so jddoe has a good point. For light storage 125psf agrees with ASCE requirements.

Some producers may think your projects are too small, but that is not true of all manufacturers.

Here's a list of all PCI certified Hollowcore producers.

http://www.pci.org/find/precaster_search.cfm

For 125psf load you'll likely be needing a 6"+2"topped or 8" untopped for a 24ft span.