I am planning to tile 3 bathrooms and have used various deflection tools. One outstanding question is the grade of wood for my joists.

Joists are marked as follows:

ILMA S-Dry

135 3

S-P-F

SPF is Spruce-Pine-Fur

ILMA is The Independent Lubricant Manufacturers Association

S-DRY is surface dried.

What is the 135 for and the 3?

Is 3 possibly the grade?

My joists are 1.5 by 9" (some ~9 1/8"), 16" oc, and 13'4" span.

Everything so far indicated that using the L / 360 deflection rule, they will not support porcelain tile. Arg!

Are there any alternatives for tiling? I can not sister the joists since there is a full celing beneath each bath.

Thanks

JD

Why would a lubricant manufacturer be grading framing lumber? More likely, it's the Interior Lumber Manufacturers Association. If your joists are truly #3, their maximum span for 40 PSF Live Load is 11'-9". If they are #1 or #2, their maximum span is 15'-5", according to the table in the building code.

I can't find an explanation of their grade stamp, but if your joists are truly #3 SPF, there is no hope. If they are #1 or #2, which they should be, the deflection for your span is 0.4345 inches, and 1/360 would be 0.4444 inches, so you should be OK, by a hair.