Number of subfloor plys

[efsolomon]

I am beginning a 28x64 cabin and wondering how many layers of subfloor to install.  My 2x8 joists on on 16" centers.  I had a similar house built years back and the builder installed 2 layers of 3/4 plywood.  The first before the walls were erected and the second layer afterwards.  Everything I read and see has only one layer.  I plan on using 3/4 Advantech. Should I use 2 layers running perpendicular to each other as he did?  What are the advantages/disadvantages of doing so?  Other than cost of course.

[MountainDon]

With joists on 16" centers 3/4" Advantech makes for a pretty solid floor. If you wanted greater stiffness I'd suggest checking if you can get the Advantech in a thicker panel. They make 7/8", 1" and 1  1/8" thicknesses. That would be preferable to two separate layers.

What kind of finish flooring are you going to install?

[efsolomon]

Thanks so much for the quick response!!!  As this is a build-as-I go project, I'm not sure exactly what the finished flooring will be, perhaps an assorment.  I would like to build the structure to handle whatever may come up in the future though if that matters.

[MountainDon]

If there's any chance you might want to use ceramic tile or natural stone you should run the joists numbers through this calculator to see if the floor will be stiff enough.

http://www.johnbridge.com/vbulletin/deflecto.pl

[Bobmarlon]

  I think 1 layer or 3/4 inch sub-floor is usually sufficient  But I have seen an extra layer of plywood in bathrooms and kitchens I guess this is because the floors in these rooms support more weight.     You'll have lots of time to research this since you wont need the extra layer till the roofs up.   

[texasgun]

I dont know if you already did your floor but on my current house that I built I used 3/4 t&g plywood and after everything like sheetrock and mud was done I did 1/2 on top. The 1/2 (non t&g) covered everything I could not clean off of the first floor and covered a little water damage from exposure on the 3/4. The 3/4 went under the walls and the 1/2 was fitted up to the sills and 30# felt went in between the two layers. I sealed the edges with silicone calk and used all my scrap 2x material all the way around for blocking for baseboard trim. In areas I wanted tile I ommited the 1/2 plyood and used tile backer. Dont know if it helps anyone but its the way I did it plan on the same for my cabin if it is a bad idea maybe someone else will chime in. I feel adding the new clean layer saved me lots of time but not sure if it saved me any money.

[dug]

I feel adding the new clean layer saved me lots of time but not sure if it saved me any money.

Time is money!