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Russell8 11-29-2010 06:32 PM

Basement span without support?
 
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

jklingel 11-29-2010 11:40 PM

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.

jlhaslip 11-29-2010 11:49 PM

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.

ENGINEER10 11-30-2010 12:07 AM

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.

Russell8 11-30-2010 03:50 PM

Hi there

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

mrgins 11-30-2010 03:55 PM

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

ENGINEER10 11-30-2010 04:08 PM

Quote:

Originally Posted by Russell8 (Post 543107)
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.

jklingel 11-30-2010 04:53 PM

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

ENGINEER10 11-30-2010 09:49 PM

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

jklingel 11-30-2010 11:11 PM

Quote:

Originally Posted by ENGINEER10 (Post 543389)
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:

Joe Carola 12-01-2010 05:43 AM

Quote:

Originally Posted by jklingel (Post 543427)
Sorry for not specifying. A flat truss is essentially a BCI/TJI.

Those are I-joists, not floor trusses.

ENGINEER10 12-01-2010 11:39 AM

Quote:

Originally Posted by jklingel (Post 543427)
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.

jklingel 12-01-2010 03:23 PM

Quote:

Originally Posted by Joe Carola (Post 543478)
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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