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Old Posted Jan 16, 2012, 8:20 PM
PhilGArch PhilGArch is offline
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Flooring Design Question

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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Old Posted Jan 17, 2012, 3:44 AM
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Tony Tony is offline
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Typical residential construction is approximately 3 metres (10') per floor.
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  #3  
Old Posted Jan 17, 2012, 7:16 PM
Rizzo Rizzo is offline
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I'm no engineer so maybe someone more qualified can speak but since this is for a studio project, just do a 6" slab concrete. Your thickness depends on alot of things, but you can get some decent spans between typical residential unit sizes without beams dropping down into your space.

If you want to do a steel low-midrise building, use hollow core concrete planks for your floor decking. You can run conduit through them, and get some decent spans. Use around ~6-8" for 20-30' span.

You'll find 7'6" between finish floor and finish ceiling, but it's not all that desirable. Do like 9' floor to floor minimum so you can get an 8' clear minimum after you add in slab floor coverings, and a finished ceiling.....that is unless you decide to expose it.

Remember alot of your HVAC and plumbing can be run between walls and in chases. It doesn't have to cross through living spaces.
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Old Posted Jan 17, 2012, 9:00 PM
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scalziand scalziand is offline
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In general, concrete is going to get you the thinnest slab, so you should probably go with the 6' slab that Hayward suggested.

The thinnest steal beams that are practical to use are often 8'' and up, plus they have a thin 2-3'' concrete slab on top of the beams.

With wood, 2x8 or maybe 2x6 joists could be used, although that will require an extra inch or so for the subflooring.

With wood and steal, sometimes you can have the utilities go through the beams.

Last edited by scalziand; Jan 19, 2012 at 8:11 PM.
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Old Posted Feb 18, 2012, 1:12 AM
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scalziand scalziand is offline
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This month's Modern Steel Construction has some interesting articles on flat plate floor systems using hollow precast panels resting on beams embedded in the slabs.

http://www.modernsteel.com/Uploads/I...flat_plate.pdf

http://www.modernsteel.com/Uploads/I...el_support.pdf
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  #6  
Old Posted Feb 25, 2012, 1:27 AM
JohnMarko JohnMarko is offline
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Quote:
Originally Posted by PhilGArch View Post
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!
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".

Last edited by JohnMarko; Feb 25, 2012 at 1:50 AM.
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