deflection question? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-19-2007, 10:52 AM

I haven't seen this mentioned here before. I know deflecto should always be followed. But what about the case when a small bathroom is near the outside wall as opposed to being in the middle of the house. Wouldn't the joists below have less deflection at the ends where they rest on the outside wall than in the middle section of two supports (outside wall and a beam in the middle of the house)? Can this be considered in calculating deflection?


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jay f
08-19-2007, 10:55 AM
No. Deflection happens down the entire length of the joists (between supports), regardless of placement of rooms.

08-19-2007, 10:58 AM
Gabe, the number that the deflectometer gives is a measure of stiffness. The actual amount of deflection is not important, but rather, the relative stiffness of the structure is important.

08-19-2007, 10:59 AM
I might consider it in my house, Gabe, but not in yours. Technically, I shouldn't consider it in mine. Load the middle of that joist system and the ends are gonna move some, too. :shades:

But, as we've said repeatedly hereabouts, it's the between-joist deflection that's most likely to get your tile installation, anyway. So if you're fixin' to cheat, don't cheat on the subflooring and don't use the substrate manufacturer's minimum requirements if you can help it.

My opinion; worth price charged.

Looks like I agree with them fast guys, too. :)