spf not syp, guidance needed

[msaunders]

My joist (2x8's on a 101/2 foot span, set 18in. apart) are spf not syp what does that mean? My 'Calculate deflection' is 325. I wanted to put ceramic tile down. Am I just out of luck? Is there a solution? What type of sub floor will be best?

[cx]

Welcome, M.

SPF stands for Spruce/Pine/Fir and there are generally two versions of it, Northern and Southern.

It's not the best stuff for floor framing, but it's not all that uncommon.

More uncommon would be 18" on center joist spacing. And not sure how you got L/325 from the ol' Deflectolator without you used 16" in your calculation.

If your house was built to code within the past fifteen years or so, chances are the floor framing met the necessary L/360. And if your joists are #2 or better, I can find you a span table that says what you've got will work with 40lb. live and 20lb. dead load.

What do you currently have for subflooring?

My opinion; worth price charged.

[fn_benthayer]

19.2" O.C. will net close to 18" between the joists.

Just a thought...

[msaunders]

I've pulled up more of the floor. I have a 5 " deep, 8 foot long bathroom. The joist run the lenghth going under the tub. I can see 3 of the joist. The first space between joist comes from a joist under the hall, I'll have to crawl under the house later for the actual space between joist but the next space measure 16" from center to center. the 3rd space measure 16 and1/2 and to that joist a 2x2 has been added to it lenghth wise. The joist does not seem to be damaged, it seems to have been added to secure part of the subfloor to. The next space is 15 and1/2 to center joist in this space fits the toilet. The final space disappears under the wall. On top of the joist was/is a 3/4' piece of plywood. The plywood was nailed and glued to the joist. On top of the plywood was laminate. the plywood is water damaged and needs to be replaced. This section of the house was an add-on built 20 yrs. ago. Any input is greatly appreciated. Thanks.

[msaunders]

Ok, ripped the subfloor out. Scabed 3 of the 5 joist with 8 ft sections of 3/4 by 7 in plywood sandwiched with an 8ft, 2 by 4, screwed in each layer. The one joist damaged by water was also scabed with plywood as well as a new 2x8 joist. A pole jack with 1x6 metal plate was placed under this damaged/new joist. (Found out this Joist was never truly supported it was boxed to the 2 surrounding joist.)
Joist are now 2x8's, 16 in on center, over a 10 ft span.
I believe I can now tile?? as soon as I fix the plumbing

Questions
I plan on using 3/4 " plywood or as close to it as I can get for the subfloor.
Then what do I use???
backerboard or plywood?
Can I screw the backerboard to the subfloor or must I use mud?
Can I simply use 1/8 or 1/4 plywood screwed into the subfloor and mud and tile over it?
Should I put down a water sealer on the backerboard or plywood before I mud and tile? What type should I use?
If I need to use backerboard what type do I use? is 1/8 " ok?

Please help.
I think I'm in over my head.
Michelle

I'm glad I opened it up but what a mess!

[scuttlebuttrp]

Yes. BC sanded ply. 3/4" tongue & groove.
What are you installing? Stone? Ceramic? Pennies?
Don't know yet.
Don't know yet.
Never use 1/8" or 1/4" ply under tile.
Maybe. Are you above grade like a second floor?
Don't know yet.
The thinnest backerboard is a 1/4". Ditra is only an 1/8".
We can help more just as soon as you let us know what your doing.

[jgleason]

Hi m,

I merged your threads. We have a "one project, one thread" system here, makes it easier to follow that way.

[msaunders]

Thanks, I couldn't find my old thread but I'll admit I didn't look to hard.
Sorry
thank you.

back to my saga...
I want to put down 11 1/2" porcelain ceramic tiles.
T&G plywood? I didn't know. I guess I can take the other back.
If not can I use what I have. It's BC sanded 23/32 plywood.
I was going to run 2 sheets the length of the joist, piecing at the joist center and filling with wood putty.
The bathroom sits over a 2 1/2 ft to joist crawl space.

Thanks for all guidance.
Michelle

[bbcamp]

If the sheets meet over a joist, such that the seam is completely supported by the joist, then you don't need the T&G plywood. If the seam crosses the joists, you can install blocking to support the seam, and you won't need T&G.

Do not fill the seam with anything. Leave a 1/8" gap and forget about it. Leave a 1/4" gap at the walls. You can caulk that if you want.

[msaunders]

Learning all the time
The old subfloor was glued and nailed. I was just going to screw down the new subfloor, is that ok?

[bbcamp]

Use construction adhesive between joists and new subfloor. No squeaks, no movement. Life will be good.

[cx]

Looks like there might be some confusion about the orientation of your plywood sheets, too, M. All subflooring sheets must be laid such that the face grain is perpendicular to the joists. You got that part?

My opinion; worth price charged.

[msaunders]

All subflooring sheets must be laid such that the face grain is perpendicular to the joists...

Ok , good to know, so I need to lay the board across the joist. So I will add blocks between the joist where the plywood seams. Then use construction adhesive and screws.