Expert: Nazim Nice - 7/9/2009

Question
Hello,

I am trying to design a commercial building.
The first three floors (1-3) I would like a lot of open space.
I would also like to have it be ten feet from floor to ceiling for each of the first three floors and very sturdy.
Then, the next three floors (4-6) I would like to be separated into to two floors (4-5), where each floor is a floor and a half tall.
So, floors four and five would be fifteen feet from floor to ceiling.  I would also like a lot of the ceiling for four to be open space.

QUESTIONS:
For the first three floors, how wide and far apart should the support pillars be for a very sturdy floor with a lot of open space?
How thick should each floor (ceiling to floor above) need to be for industrial style ceilings/floors?

Thank you very much.

Kirt

Answer
Hi Kirt,

Are you working with an architect and structural engineering yet?  I think you would be wise to since it sounds like you have some good ideas that could be worked out with some more details.  Things you may want to consider:

Not sure what materials you are thinking of using for the structure: concrete, steel trusses, steel girders and beams, wood (probably not for a structure this tall).  Each have different properties and benefits and disadvantages.  For example, steel trusses can have a long span, but generally won't produce as solid a feeling floor as a full concrete structure will.  Concrete can have longer spans if it's post-tentioned.  So there are many choices that can be examined, but the final choice is usually a balance of what you want to achieve, what makes sense structurally, what is available in your region, what is required by code (especially fire ratings) and what it will cost.  

Regarding your questions, how wide and far apart columns should be will depend on the materials you select and the loads.  I would look at the use on each floor and do some space planning to see what spacing makes sense for your use (like an office use - do layouts with standard office furniture dimensions).  

How thick a floor assembly should be will be dictated by the material choice -- but consider doing a deeper than normal truss so that hvac ducts can run through the truss members.  This might also get you longer spans and fewer columns.  Otherwise you can layer the structure with the hvac ducts below, but the total dimension may be more than if you integrate them.  

Hope this helps get you started.  Good Luck!

Nazim Nice
Principal / Architect
http://www.motion-space.com
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