Deflection

[CaliGrown]

House is older; want to check deflection before considering tiling.

Joists are in good condition, 5 1/4" H by 4" width. 48" on center between joists. 5' span between joist supports. 5" by 1 1/8" Tongue and Groove planks spanning perpendicular to joists.

What deflection am I looking at? (Deflectolator only goes up to 24" o.c so I'm thinking the deflection rating won't be adequate for tile)

Thank you in advance everyone.

[CaliGrown]

Forgot to mention, if tile is an option I will be putting down at a minimum 1/2" plywood over the planks. After removing the existing particle board and vinyl. Along with setting Ditra on top of the plywood.

[cx]

That's a pretty typical Left Coast floor framing, Chris, with the exception of the thickness of your car-plank subfloor. Those are usually closer to a nominal 2x6 and about 1 1/2" thick. Our former engineer has determined that those floors, with the addition of the half-inch plywood, were suitable for a ceramic tile installation. With the reduced thickness of your boards, I can't really say where your would rank in between joist deflection. If I were gonna fly by the seat of my pants and tile over the floor anyway, I think I'd at least wanna increase my plywood thickness to 3/4" or better.

You can run your joist structure through the Deflectolator. Simply reduce the joist width by half and reduce the spacing by half and you'll get what you need. That part's linear.

My opinion; worth price charged.

[CaliGrown]

Okay thank you CX, I wasn't sure how to accommodate the measurements to account for 48" o.c.

With the accommodations, the deflectolator gives a value of L693 which is well beyond L360, so I should be good to go with a ceramic.

I will plan on using 3/4" or 1" plywood.

Would it be best to run the plywood perpendicular to the planks or in the same direction perpendicular to the joists?

[cx]

Originally Posted by Chris

...the deflectolator gives a value of L693 which is well beyond L360, so I should be good to go with a ceramic.

That provides for the deflection of the joist structure only, Chris. The between-joist deflection is generally the more critical factor and I am not equipped to tell you that what you have is or is not adequate to your application.

The difference in subfloor thickness between 1 1/8th-inch thickness and 1 1/2-inch is substantial, but I'm not engineer enough to tell you just how substantial. See my warranty information below.

All layers of structural subflooring must be oriented with the strength axis perpendicular to the joist structure. Here is a good article from our Liberry showing what I think is the best way to install that second layer.

My opinion; worth price charged.

[CaliGrown]

Thanks for the good information CX. Could you resend the link, I'm getting a 404 Not Found Page.

I'm guessing a structural engineer would be the one to say what the between joist deflection is?

[cx]

Dunno why that would be. Izza only link I have for it.

If that doesn't work, look in our Liberry at the bottom under Wood Framed Floors, post 11.

[CaliGrown]

Will do, thank you. Might just be a problem on my end.