# Basement span without support?



## Russell8 (Nov 30, 2010)

Hi there

I am thinking about doing a basement, and just wanted to know how big I can go before I need to put supports in? 

Thanks Russell


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## jklingel (Dec 21, 2008)

Over 100', if you want to. The longer the span, the higher/beefier the supporting member needs to be. It all depends on how much height you are going to sacrifice for the beam, truss, or whatever it takes for your load. You will need to specify what loads you have, first.


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## jlhaslip (Dec 31, 2009)

I've done floor systems at 40 feet wide with no basement supports, but the Owner works at a Mill that build LVL, so he supplied them.
The house was single floor only. No point loads on main floor.


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## ENGINEER10 (Oct 10, 2010)

*No limit*

The limiting factor is cost, otherwise any span without supports is engineering-wise feasible.

To come up with cost first you need it designed and then ask contractors to give you cost estimates on the design. If it doesn't fit your budget go back to drawing board and redesign it with smaller spans.


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## Russell8 (Nov 30, 2010)

Hi there

Well the span is going to be 12x12 metres and the ceiling is about 8 foot high,


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## mrgins (Jan 19, 2009)

Get it engineered or call your building supply and see if there's a take-off person that can calculate the loads. I used to be that guy many years ago and it's not rocket science


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## ENGINEER10 (Oct 10, 2010)

Russell8 said:


> Hi there
> 
> Well the span is going to be 12x12 metres and the ceiling is about 8 foot high,


This is a 40' span.

12" or 14" Light-Gauge steel joists will easily and economically work with no intermediary supports.


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## jklingel (Dec 21, 2008)

... or standard roof trusses, if you don't want steel. 12 metres is no big deal. j


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## ENGINEER10 (Oct 10, 2010)

A basement does not have a roof, therefore trusses are ill advised.


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## jklingel (Dec 21, 2008)

ENGINEER10 said:


> A basement does not have a roof, therefore trusses are ill advised.


 •• Sorry for not specifying. A flat truss is essentially a BCI/TJI. Yes, a typical A-shape would make the second floor navigation a bit awkward. :laughing:


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## Joe Carola (Apr 14, 2006)

jklingel said:


> •• Sorry for not specifying. A flat truss is essentially a BCI/TJI.


Those are I-joists, not floor trusses.


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## ENGINEER10 (Oct 10, 2010)

jklingel said:


> •• Sorry for not specifying. A flat truss is essentially a BCI/TJI. Yes, a typical A-shape would make the second floor navigation a bit awkward. :laughing:


These would have to be 3 feet deep trusses spaced 12" on center.

That's much more expensive than 14" metal joists.


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## jklingel (Dec 21, 2008)

Joe Carola said:


> Those are I-joists, not floor trusses.


 Yes, a flat truss is not a I-joist, but they are essentially the same animal. Rectangular, set "on edge", etc. I have no idea of the relative expense of a flat truss, nor do I know what he is putting on top. Just another option to look into.


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