How many Piers?

[kromar]

Been reading this forum for a while,Great info! I'm finaly ready to build my 24x24 cabin in N.Central PA. I will be using post & pier construction. How many piers and how far appart should they be? It will be a one story with either 2x8 or 2x10 floor joists. The piers will be either 6x6 or 4x6.Thanks in advance!
                                                                                      Kromar

[Kodakjello]

Hey kromar! You'll have to use a beam span calculator to figure out exactly what the span should be. It depends on the expected live load and dead load of the structure and the size of the beams you want to use. The beam size is usually more important that the pier size since a 6x6 post can hold up a TON of weight. (figuratively speaking  )

Here http://www.awc.org/technical/spantables/tutorial.htm would be a good place to start!

Kodakjello

[glenn kangiser]

Hi kromar.

John posted this info on post and pier, but unless the calcs are done for your specific loading there is not an easy way of knowing how many are required.  http://countryplans.com/foundation/index.html

The only thing he has in a 24 wide is the Solar Saltbox as I recall.

I assume you would need something like 3 beams and about 6' spacing on piers to be safe but that is just a guess and there are lots of variables.  This may need to be answered by a local professional - architect or engineer if it has permits anyway.  Are you working from plans?  Your plans could influence this also - depending on if there are bearing posts or walls etc.

[John Raabe]

For a post and pier foundation you have to do a load trace from the roof on down accumulating snow. wall and floor loads to determine the maximum lbs per lineal foot that will land on the beams. From that and the spacing of the piers you can size the beams.

I do this for each of the plans I design using standard code loads for the floors and 35 psf (live load) for the roofs - enough for all but heavy snow country. Often the rafters will actually be deep enough to carry more than 100 psf because they are sized for insulation depth rather than the snow load. This is most often true of cathederal ceilings.

The 20' wide 2 story universal cottage plan has foundation plan sheets (basement, crawlspace and P&P) that could be easily modified for 24', 26' or 28' or more of width (each with a centerline bearing beam). The joists and beams would have to be recalculated for those new loads and spans but the basic layout is there. The calculations can be done by a local home designer or a builder with a beam calculation program.