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#### BlueBSH

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I am trying to figure out if I can tile this floor or not.

I measured the deflection of the actual floor with point loads and a deflection gauge, the most I have deflection wise (max out of all readings) when on joist or between joists is 0.40" across a 15' span, L/360 says .5" is max, so it appears to be in spec... all the span charts and the deflect-o-later tells me no though...

joists are 2x10 unknown species, assuming SPY 16" O.C.... all have cross bracing multiple times across the span length... decking is 1" OSB which is glued and screwed down.

the area that would be tiled is 12 ft of that span long and 9 ft wide.

So is it in spec based on the gauge readings? or still a no just because?

#### Daniel Holzman

· Civil Engineer
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5,832 Posts
The deflection in the L/D formula refers to the total deflection at the center point of a joist or beam, based on the combined live and dead loading. The dead load is simply the weight of the framing, and is commonly taken to be between 5 and 10 pounds per square foot. The live load is a code driven input, and is typically either 20, 30 or 40 psf depending on the type of room you are analyzing.

#### JazMan

· Tileguy
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Excellent explanation Daniel.

BlueBSH,

I'm I to assume your span is 15' 0", 2x10 unknown species and grade, 16" oc. in good condition. Built in 1996.

I believe your floor absolutely meets min. specs for general flooring at 40/10 load. I use 50/20 when consulting the charts for ceramic. So I say you should stiffen those joists up to be safe. Did I use the right numbers of your floor's framing?

Jaz

#### BlueBSH

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Excellent explanation Daniel.

BlueBSH,

I'm I to assume your span is 15' 0", 2x10 unknown species and grade, 16" oc. in good condition. Built in 1996.

I believe your floor absolutely meets min. specs for general flooring at 40/10 load. I use 50/20 when consulting the charts for ceramic. So I say you should stiffen those joists up to be safe. Did I use the right numbers of your floor's framing? I can only see a small area where I have access holes for plumbing runs without pulling the drywall down in the room below. a stud finder also seems to indicate this since I am getting a start and end about 3" apart on joists.

Jaz
yes, framed in late 1996 with 2x10's appears to by SPY wood but not sure at 16" O.C., from what I can tell the joists under the area (a bathroom) appear to also be sistered when framed almost like they expected it to be tiled?

The flood feels like it has no bounce to it, I'm sure there is some though... had a tile guy look at it in the past and he said it seemed ok to tile based on what they checked.

But like everything else you go online find a deflection calc and boom a big no for ceramic (the deflect-o-later calc says that)

How I did a quick test was like this, laser line across the floor from where I know it's supported on one end across to the other, measured the height on both ends where the support under is at one end (outside wall) was about 1/4" lower then the other end, but that's a framing issue... where I knew there was a joist at I put 300 lbs of weight and had minimal deflection from the floor to the laser line (About 1/4"), moved the weight to different spots along the floor and measured the deflection, not much different across the floor on joist and off joist.. I know it's a point load basically that occupied 1sq ft of space when loaded. it was just a simple test with what I had to work with at the time. I also tried the old jump test to feel for movement, felt solid, not as solid as concrete, but didn't feel like it moved much at all. At dead center I got the ~3/8" drop when loaded

#### JazMan

· Tileguy
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Did you mean to say the species is SYP, Southern Yellow Pine? Do you know their grade? See any stampings? What do you mean the joists "appear to be sistered"? If you look at them and there's two bolted together, then there's no question. Have you been able to look yet?

The Deflectolator also suggests what I said. Your numbers are marginal for tiles and good sleeping. But the new info you mention may change all that. I am not confident I know the specs of your framing.

Jaz

#### BlueBSH

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Did you mean to say the species is SYP, Southern Yellow Pine? Do you know their grade? See any stampings? What do you mean the joists "appear to be sistered"? If you look at them and there's two bolted together, then there's no question. Have you been able to look yet?

The Deflectolator also suggests what I said. Your numbers are marginal for tiles and good sleeping. But the new info you mention may change all that. I am not confident I know the specs of your framing.

Jaz
found one stamp hard to read by says SYP NO2 S DRY 1996

They appear to just have two joists side by side cant tell if nailed or bolted from where I can see in the access holes, they cut out a part of the subfloor right over two joists for the tub plumbing.

#### JazMan

· Tileguy
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I guess you're saying only one set of joists are sistered or at least next to each other. That does not make the floor joists sistered.

So, SYP #2 @16" oc spanning about 15'. I'd try to stiffen them up if at all possible. But from the lack of info you've supplied, it sounds like you are not able to see the framing very well. The good thing is that your 1" OSB is stiffer than what most floor are built with and the joists' deflection is not as critical as the subfloor deflection. So you may be ok for ceramic/porcelain, but you're on your own.

Another thing you could do is to try to find a mortar made by Hydroment/Bostik that claims it'll work well even at L240. It's called Reflex. There's a distributor in Johnstown PA that has or can get it for you.

Jaz

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