16 x 36 block perimeter foundation questions

[jhivy]

Planning a 16X36 house based on the 16 X 28 plans.  I will use a block perimeter foundation.  Per the plans, I see no floor joist  support along the center line of the house.  Am I missing something?  A 16' span seems like a long distance only supported at the ends.  That also calls for long (expensive) framing members.  Can I add block piers along the center and use shorter floor framing members?  Thanks.

[rick91351]

It is easy to go longer just not so easy to go wider.

You can plug in your span in the follow calculator.  Not hard and in fact is sort of fun.

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

Using 2X12s number two and better Doug fir on 16 inch centers I am showing 18 ft and one inch. 

Answer to your other question can you add piers and a center support.  Yes you can.  And you could add a center beam and toe nail your 2X12s to that or you could go with shorter joists.  You can run the dimensions as to what is needed with the handy link above. 

Question is is that a good idea?  I would have to say no.  I would go with the 2X12s simple framing less chances of squeaking, other failures.  Farming is a lot like anything else in life.  Simpler the better the more parts you have the greater failure rate on down the line.  But it is just my opinion and I am not a framer or even much of a builder.

rlr           

[rick91351]

Hey  jhivy

This might help as well the Code is under section R502.3

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_5_par014.htm

and refers to the following PDF

https://docs.google.com/viewer?url=http%3A%2F%2Fwww.awc.org%2Fpdf%2FSTJR_2005.pdf

OPPSSS!!!  FORGOT where are my manors ?      From Idaho

[Squirl]

16 ft isn't a large amount.  If you lay 8" block and a 2x8 sill plate, that knocks off 7.5" from each side.  So the joists are only spanning 14'-9".

2x10 SPF No. 2 16" O/C will can span 15'-5".  If you are worried about stiffness you can upgrade to No. 1 boards in some species.  Around me the 2x8s - 2x12s Douglas Fir have had about every 4th or 5th board as No. 1.  It is a big step up in strength just by picking through the pile and it is the same price.  One shipment almost the whole stack of 2x10x12s was No. 1.

Sure you can add a center girder and piers and most importantly a footing to displace the load(properly sized of course).



I originally didn't plan on it.  I wanted the taller joists just for the insulation value already.  For me by the time I added in the work and cost of the center girder, along with the thicker subfloor I had to buy, it was a wash in cost.  Actually the center girder ended up costing more because since I had to go with thicker subfloor for the wider spacing on the joists, I upgraded to a rot resistant one called advantech.

In building it is usually 6 one way, a half dozen the other in terms of cost.   

BTW