Deflectometer (or whatever it was called)

[Andrew Pitts]

Just used the deflecto-----what a great tool you've provided here. I was staying awake trying to be sure that my floor would be ok for ceramic tile. Kept thinking, maybe I'm not truly understanding how this calculation is done but fell into your "deflecto" while reading on your site again. Thanks for providing such an easy to use tool.

[bbcamp]

You're very welcome! Stick around and talk about your project!

[RobC]

I am guessing that the deflecto assumes a total floor thickness of 1 1/8".

What if your subfloor and underlay are actually more than this? For example, I have engineered 2x10 (2.5" flange, 9.5"h) I-joists @16" o.c. (15' span) with 5/8 TG subfloor and 3/4 spruce plywood. My plans did not call for any blocking, but I put some in anyway.

The deflecto gives me L/530 but I am wondering if the extras give me enough to support natural stone. Anyone know?

Thanks!

[Andrew Pitts]

Originally Posted by bbcamp

You're very welcome! Stick around and talk about your project!

OK Bob, just submitted my project as a thread.

[bbcamp]

RobC: The deflectometer doesn't assume anything about the subfloor, and it doesn't do I-joists. We have to know the manufacturer and model number and look 'em up. My experience is that your will not be stiff enough for stone.

[RobC]

Bob,

My joists are made by Alljoist, model AJS 20, 9 1/2" high by 2 1/2" wide flange.

There is a section in the manula for Maximum Floor Spans, allowable stress design - 100% load duration 'glued and nailed subfloor'. Under that heading is a table indicated Live/Dead Load (psf), the largest section is 40/30, at 16"o.c the maximum span for L/360 is 16'11". This is the same value found under the 'improved performance' section for L/480 as well.

So, in addition to everything I posted above, my subfloor is glued and nailed, then I screwed it to the joists each 6". The underlay was screwed down every 4".

I suppose that I could always jerry rig a black spray paint can on top of a ladder about a 1/2" away from my ceiling, then jump on the floor above it. If I have black paint everywhere I will know that my floor deflected 1/2". You don't need an engineering degree for that!

[bbcamp]

Is there a website? I collect those things, you know.

[davem]

Googled,found this: http://boise.bc.com/ewp/install_alljoist.jsp

[cx]

Originally Posted by RobC

I suppose that I could always jerry rig a black spray paint can on top of a ladder about a 1/2" away from my ceiling, then jump on the floor above it. If I have black paint everywhere I will know that my floor deflected 1/2". You don't need an engineering degree for that!

Very creative, Rob. Potentially messy, but creative, no less.

Only problem with your test is that for natural stone you're only allowed a maximum of a quarter-inch deflection in the center of that floor. And you gotta have a couple friends help you do the jumpin'. Well, unless you got you some really big friends.

My opinion; worth price charged.

[greg ziegler]

boise I-joists did them for the first time in the last house we framed: we liked we liked that floor will never move easy to install whole system but be careful with which size fasteners you use real careful different sizes for different I-joists if some-one would be building and erecting there own I strongly suggest to use this system. very happy with whole system