Quote:
Originally Posted by PhilGArch
Hey All,
So I am doing a project for studio class where we are designing residences and I have been task with looking up typical or minimum floor to ceiling or floor to floor heights for residential structures.
I know 7'6" is the standard minimum and 7" for kitchens and bathrooms.
But as far as floor slab thicknesses I have been having trouble finding anything solid.
So my question is what are the minimum thickness for concrete, steel, and wood floor slab construction in residences.
Thanks for the help!
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We do this in our sleep (major hotel and high-rise structures):
Typical floor to underslab height is 9 feet for residential/hotel high-rise construction; 8 feet floor to underslab is the industry standard for single and two story residential construction, not 7'-6", altho I know of an Architect that used the building codes MINIMUM standards as his MAXIMUM standards - he had 7'-6" floor to underslab. The HVAC and utility servicing was thru vertical chases. For horizontal HVAC utility plenums, add a minimum of 24-30 inches between ceililng and underfloorslab.
For a building about 13-20 stories:
Concrete construction:
20x30 inch columns @20-30 feet on center maximum
8.5"=9" thick slabs for floors and roofs
13 inch slab thickness for usually ground floors with higher concentrations of point loads (think "cash/coin carts)
For same in steel:
W14 columns about 20-30 feet on center maximum
W21 steel beams @ 30 feet on center maximum
4 1/2 inch metal deck w/5 inch concrete topping = 9 1/2 inch total thickness floor slab
We've also used 3 1/2 inch decking with 4 inch concrete topping for roof slabs.
For wood construction: Use the International Building Code (IBC) tables.
Generally follow the column down the middle of the table.
Up to 2 stories (can be up to 4 stories):
2x4 studs @ 16 inches on center for most cases, "western platform" framing.
2x6 studs can be used for exterior walls (but 2x4 is most common). 2x6 studs are generally used for commercial exterior walls and structures taller than 2 stories.
2x12 joists @ 16 inches on center work fine for everything, but you can go less than 12 for some spans. Spans are determined by IBC table.
I've never seen 2x6 or 2x8 joists in the industry generally - maybe for custom homes for special conditions where space is limited and the spans are really close, but no builder would stock different sizes on-site for a project - too much chance to get something wrong and too costly.
3/4 inch minimum plywood decking, altho 1 1/8 inch T&G decking is used for some instances. Again, use IBC tables. 1 1/8 inch decking is used for 24 inch joist spacing and 4 foot rafter spacing. 2x4's can span 48 inch spaced 4x rafters/joists or 24 inch spaced 2x rafters/joists.
I designed a home with the garage on the top floor (house was "downhill") with 1 1/8 inch T&G decking over 2x12 joists at 12 inches on center with specifically designed wood beams to support the floor joists.
For multi-family projects, the 30 foot spacing is ideal, as it allows for two side-by-side rooms/units without a "forest" of structural columns or bearing walls.
If you're designing parking below the units, try designing the spacing for parking spaces first, then allow for the structure to determing the 2-bay unit dimensions. 30 foot spacing allows for 3 parking spaces or two parking access aisles - and it works for the 20-20-20 (19-22-19) spacing for a row of parking spaces on either side of a single access aisle.
Open web steel and wood joists allow for the horizontal location of utility runs, and custom designed wood joists (with a solid wood top and bottom chord and solid 3/4 inch thinck web) are also economical for larger multi-family and commercial projects. And the different manufacturer has span/size tables for each product item. And they'll gladly provide you with project-specific size information FOR FREE if you give them a call!!! These are great guys to talk to - even before this Depression started...
That should get you started.
The "Western Wood Products Association" manuals are really helpful for easy computations for wood construction, especially for cantelevers, and overhanging floors.
Pay attention in Structures class - and if you're like me, I failed until I got together with other "dummies" (like-capable/knowledge deficient students) like me to finally understand the concepts of basic Structures. Those who already "get it" can't remember how it is to "not know" and can't "teach down".