help with new home plans, please [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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05-27-2004, 11:40 PM
I have several questions regarding plans for a new home. If it's too much to ask just say so. I want to make sure I do things right... I want to be able to upgrade to natural stone tile in the kitchen (can't afford that now). Also, I want the floor to be stiff in general.

1) What deflection (L/x?) should I aim for if I want "solid" feeling floors. If it's natural stone capable (L/720), will it feel solid? Plans call for 2x10 joists, 16" OC, 10' span with exception of #5 below.

2) What type/thickness plywood subfloor would be the minimum?

3) Plans call for 3" round steel support poles in basement. Stock plans are for 8' walls. I thought about 4" poles for 9' walls. Do these poles that support the beams make much difference for floor stiffness above?

4) Plans call for W8x18 beams with 12' spans (I am increasing span to 12'8" each). Do I need to change beams?

5) My home plans call for the following under the kitchen (which is the only part with a greater than 10' span):
-2x10 joists (every other doubled)
-16" OC
-16' span!
When I calculated this (I assumed every other doubling was approx. equiv. to decreasing the spacing to every 10") -- it was nowhere near sufficient for natural stone.
I then calculated doubling every joist (assuming that was equal to 3" width) with 12" OC and came up with L/716. Is that close enough to L/720?

Are my assumptions correct?

Thanks for any and all help.

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05-28-2004, 06:00 AM
Welcome, Mac!

No, you didn't ask too many questions! And yes, now's the time to get the answers and build your house to accomodate your future plans. :D

1) If it's natural stone capable, it'll feel solid to everyone who's ever lived in a wood framed home. Those who have always lived on a slab floor will be able to tell the difference, but it won't bother them at all.

2) If you are planning for stone, you should have 1-1/4" of plywood. It can (and should) be in 2 layers, 3/4" and 1/2".

3) You won't see any difference in stiffness with either pole diameter. I'd stay with the 3 inch. You only need to increase the pole diameter if you significantly increase the height. 1 foot is not significant.

4) Probably not, but I'd need more information to be sure. How much floor is supported by the beam, i.e. what is the joist span on either side of it?

5) L/716 is close enough if you used our calculator, and you are specifying the proper building materials (don't tell anyone, but there's a little fat in the calculations :D ) However, your framing is going to be very expensive. Consider pre-engineered I-joists or trusses for these spans. Tell the dealer that you are planning for stone and you want L/720 or better.

This sounds like a great project! I do recommend that you have your plans checked by an architect or engineer (this advice board doesn't count in court or at the building inspector's office) just to make sure we haven't overlooked anything.


Steven Hauser
05-28-2004, 06:45 AM
Bob gave you a very good answer indeed.

I only add the following.

Have a nice day!

05-28-2004, 05:55 PM
Thanks for the input - this is a great site.

I talked to my home builder - he said he would use TJI joists (the 11 7/8 by 2 1/16 ones. The only tables (followed link from liberry) that I could find on TJI's site listed L/480 or L/360 configuration. How do I extrapolate to L/720 (ie. what should my spacing be)?

Thanks again.

05-28-2004, 06:05 PM
Hi macdad.

You can't extrapolate out to L/720. Afraid you'll have to call the joist manufacturer for the data. There are just so many different ways these manufactured joists can be engineered and assembled, there are no standard numbers you can use like is the case with dimensional lumber.