Bathroom Floor Remodeling Advice Needed

June 04, 2019, 10:39 AM

Rev. A. J. Forsyth

My bathroom is in need of a new floor, badly. The floor now consists of Douglas Fir tongue and groove over a 1" by 12" subfloor. Over the past 111 years, someone cut a massive access panel in the fir to get at the plumbing below. Repairing, refinishing of the fir is not an option.

My question is should I rip up the fir and subfloor, make a new subfloor out of the appropriate modern material and cover with cement board before I lay the tile, or should I just put the cement board over the existing 1" X 12"s? The gap between the 1' X 12"s is roughly 3/8".

June 04, 2019, 10:54 AM

arcwelder

If it were my house I'd replace the subfloor with Advantech, glued and screwed to the joists. Then go schluter.

Arc.
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June 04, 2019, 10:56 AM

Skins2881

If you are laying tile, I highly recommend heating it.

June 04, 2019, 11:10 AM

MattW

quote:
Originally posted by arcwelder76:
If it were my house I'd replace the subfloor with Advantech, glued and screwed to the joists. Then go schluter.

All day every day and twice on Sunday.

More work, but it’s done right. Chances are the 1”x12” is brittal as hell and you’ll fall through it once the wood floor is up. Wouldn’t chance laying tile on a compromised sub floor.

June 04, 2019, 11:24 AM

Rev. A. J. Forsyth

quote:
If it were my house I'd replace the subfloor with Advantech, glued and screwed to the joists. Then go schluter.

Those products look great. Thanks for the info guys.

June 04, 2019, 11:31 AM

arcwelder

PL400 is the glue, stainless are the screws. Sister as needed to level the floor, use PL and Headlok lags on the sisters. 2x4 sisters if it's out a lil, more if it's real bad.

June 04, 2019, 03:41 PM

08 Cayenne

What Arc said but calculate deflection in the floor.

June 04, 2019, 03:51 PM

arcwelder

quote:
Originally posted by 08 Cayenne:
What Arc said but calculate deflection in the floor.

Uh, no one does this.

What people do, is look at the tables in the code book, or get an engineer if necessary. Which, unless the joists are grossly undersized, damaged, or have chunks cut out, isn't needed. But nobody calculates deflection in a bathroom floor just cuz. It supported a load before, and if you glue and screw Advantech or another plywood product, it'll be stronger than the joists alone.

Fixing any structural deficiency, leveling the floor, and using a decoupling membrane, you can do it all without calculating the deflection of the floor.

June 04, 2019, 06:22 PM

ridewv

quote:
Originally posted by Rev. A. J. Forsyth:
My bathroom is in need of a new floor, badly. The floor now consists of Douglas Fir tongue and groove over a 1" by 12" subfloor. Over the past 111 years, someone cut a massive access panel in the fir to get at the plumbing below. Repairing, refinishing of the fir is not an option.

My question is should I rip up the fir and subfloor, make a new subfloor out of the appropriate modern material and cover with cement board before I lay the tile, or should I just put the cement board over the existing 1" X 12"s? The gap between the 1' X 12"s is roughly 3/8".

I assume they cut entirely through the flooring, 1"x12" subfloor too right? If done properly, the cut joint over joists and it's solid, and and additional 5/8" finished floor height isn't a problem, you could simply leave everything and overlay it with 1/4" Hardiboard. If the added height is an issue do what was already suggested and take it all up and install Advantech, then thin-set down cement board over.

June 04, 2019, 06:58 PM

bigdeal

quote:
Originally posted by arcwelder76:
Then go schluter.

Uncoupling membrane (Ditra)?

June 04, 2019, 08:49 PM

08 Cayenne

You need L360 for most times. Simple calculation, takes about a minute.

June 05, 2019, 10:11 AM

arcwelder

Yeah guy. Nobody does that.

June 05, 2019, 10:22 AM

shiftyvtec

quote:
Originally posted by arcwelder76:
Yeah guy. Nobody does that.

Well I do. In my case, second floor bathroom with existing carpet. Going in with 18"x18" travertine. My floor trusses were on 24" centers and would not support the weight of the travertine, being a natural stone there was the potential for cracking. Removed subfloor and installed 2x4 ledgers and perpendicular 2x6 supports every 16", 3/4" ply then Schluter.

It has held up great and I'm glad I reinforced the area.

June 05, 2019, 10:34 AM

Rev. A. J. Forsyth

quote:
I assume they cut entirely through the flooring, 1"x12" subfloor too right?

They cut through the fir, carefully. Then they cut "access panels" in the subfloor to get at the supply lines and drains at some point. No damage was done to the joists.

The joists in my case are true dimensional lumber. They measure 2" X 10" and are rough hewn Douglas Fir. They are 16" on center, and could most likely take the weight of a small car.

After researching Arc's suggestions, I think I'll go with the Advantech and Ditra.

June 05, 2019, 11:03 AM

arcwelder

quote:
Originally posted by shiftyvtec:
quote:
Originally posted by arcwelder76:
Yeah guy. Nobody does that.

Well I do. In my case, second floor bathroom with existing carpet. Going in with 18"x18" travertine. My floor trusses were on 24" centers and would not support the weight of the travertine, being a natural stone there was the potential for cracking. Removed subfloor and installed 2x4 ledgers and perpendicular 2x6 supports every 16", 3/4" ply then Schluter.

It has held up great and I'm glad I reinforced the area.

I'm not saying no one reinforces floors.

I'm saying no one just does equations for "deflection," and not without a reason. Paying attention to loading and structure, and using the tables is what happens. If you're going to use structural equations, you do it once for the loading and then again with the weight of your structure and make sure you have a safety factor.

There is a time for equations. It's not all the time.