On Wed, 24 May 2006 14:40:49 -0300, John van Gurp
wrote:


Hello,

Can someone give me a simple way to determine the spacing for concrete
posts under a cottage?

I am planning a 28' x 22' gable end cottage with loft, on 10" concrete
posts set below frost line.

How about the beams? Someone said to space the posts roughly every 8' and
use tripled up 2x8 for beams, glued and nailed to the full 28' length.

Any guidance in this will be appreciated. Thanks,


If you're supported built-up beams of trippled 2x8s spaced 8' oc,
then each beam mid-floor is supporting 480 PLF.
If you web-search on "built-up beam span table" you
eventually find that a 3-ply 2x8 beam spanning 8 feet
is good for 548 PLF, and one spanning 10 feet is only
good for 351 PLF. (3 ply 2x10 spanning 10' is 491#)
http://www.raisedfloorliving.com/spantables.shtml

So every 8' in both directions, internally.

The beams under the walls are only supporting 4' of floor,
but you'll also have to figure out the total of the
expected live and dead-weights of the walls and roof,
(Probably around 20PSF + snow loads) And if there's
a ceiling, around 10 PSF for that, and figure out
where that weight is applied. For a simple gable,
that's usually the side walls, unless you have posts
within the house holding up the ceiling and/or roof.
(This is a 1 story building right?)