Second floor bath remodel, 1925 house, room is gutted to the studs. Previous floor was about 1-1/2″ mortar bed topped with mosaic tiles. The floor boards were set on cleats nailed to the sides of the floor joist, so they are flush with the tops of the joists. I am adding a layer of 3/4″ ply on top of the joists/floor boards.
The floor is definately out of level … drops about 1/2″ in 3 feet at the middle. At the highest point, there is still room for 1/2″ ply. What’s the best way to level the floor? Two thoughts: add the 1/2″ ply, and use the thinset to make up the difference, or leave off the 1/2″ ply and put in a mortar bed. Or third, add the 1/2″ ply then a thin layer of mortar. Can mortar be feathered to zero? Is 1/2″ thick enough?
On the right side of the pic, you can see where the commode leaked and rotted the floor boards. Two of them were down to less than a quarter inch thick. And it rotted a portion of the celing boards in the pantry.
Whenever you are asked if you can do a job, tell’em “Certainly, I can!” Then get busy and find out how to do it. T. Roosevelt
Replies
put your 2 layers of ply down. If I read you right, it's a depression in the middle of the floor? You can use ardex at that point and just screed it if the edges are all the high points. Did I misunderstand?
"If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man." - Mark Twain
Ed:
I do this type installation all the time. The floorboards that are attached to the ledger board are fine. They provide strength at an elevation lower than was there originally.
The problem I have with this type of installation is that the structure itself has to be strong enough to do any tile. Please supply me with the size of the joists, the unsupported span and the size of the underlayment.
Assuming the structure and underlayment is fine, the best way to proceed from here is a mud bed. After all, that was what was there from the beginning. And you are better off now, because you've lost about 3/4 inch in underlayment to save elevation. Add tar paper, diamond lathe, and float an inch and a quarter mud bed.
The next best thing is to add some half inch ply and use SLC to level the room. Any depth over about three quarters will require diamond lathe.
The third best thing is not to level it at all. Just add some half inch ply and membrane it--Ditra, NobelCS, or PVC membrane.
Me? I'd use an inch and a quarter mud bed. My mud beds determine elevation of the flooring, not the other way around, e.g., elevations ought not determine heights of the setting bed. Elevations can determine what products are best to use, e.g., mud beds, membranes, etc, but only within the limits of the products.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Comrade - the floor joists are about 2x12 @ 16. It appears that the first and second floor walls align, so the span is only about 9 ft ... however, the previous wood butcher ... I mean the plumber ... has made some significant notches for the drain pipes.
I chose to add a layer of 3/4 ply on top of the floor joists cuz some of the old boards and old ledgers had water damage. That new layer is gonna stay. The question at hand is ... what do I add on top of that.
Your third choice ... not leveling at all ... is not gonna happen.
So the choice is a somewhat thin mud bed ( thickness from 1/2 to 3/4") or a layer of 1/2 ply and SLC, probably with a layer of NobleCS over that.
Or ... new thought ... SLC over the existing/new 3/4 ply, then a second layer of 3/4 ply, then NobleCS and tile. That would put the new tile about 1/4" above the adjacent floor, not the best choice cuz the floor I took out was flush. The thought on the SLC between the ply layers is that the top layer would be fully supported, not spanning any distance.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
This floor is L1626 which if fine for either stone or wood. Very sturdy floor.Thin mud beds are out of the question. Minimum mud bed is about an inch. My strong preference would be a thick mud bed, but alas, I am old and generally in the minority.So, lets concentrate on SLC and plywood.I would smear about a sixteenth of roofing cement over the floor, add tar paper or Aquabar 500 then staple 3.5 diamond lathe. Then add about a half inch or so of SLC, membrane it with Ditra, NobelCS or PVC and call it a day.If you've never used SLC, get some helpers. You can mix 2 bags per 5 gal bucket and cold joints are not allowed, so all SLC has to be dumped on the floor at once. If you are doing about 100 square feet, you'd need about 6-8 bags of SLC (check the back of the bag for precise details) which translates to 6-8 buckets, 6-8 drills, and 4-6 helpers. Don't over mix--follow the instructions. After 2 minutes of mixing, the stuff starts to set up and will be nearly solid in about 5 minutes. Dump all the SLC onto the floor at once. Push it around with a squeege a bit then LEAVE IT ALONE. If you want to have fun, bring a thermometer and watch the temperature rise as the chemicals start to work. Oh, and make Dams for the doorways and fill all perforartions. Wait a day or two, and membrane the top and tile away.Regards,
Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
If you don't mind, let's go through this one more time ...
I measured today ... joists are 24" oc. Is that still a good number?
I removed the 3/4 ply I had laid last week, and shimmed the tops of the joists level, then re-laid the ply. Tomorrow I plan to PL and screw a layer of 1/2" ply over that, then a layer of Nobel CS and tile.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
removed the 3/4 ply I had laid last week, and shimmed the tops of the joists level, then re-laid the ply.
How do you shimmed the joists?
Thanks
YCF
I put a long level across the room and measured the gap at each joist, then ripped strips off a scrap 2x4 of the needed thickness. I tacked them in place with a brad nailer, and when I screwed down the ply they were fixed in place. Fortunately the joists are almot level along their length, so I didn't have to level in two planes at the same time.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
It pay's to think some times.
Good job.
YCF
You are still good--L1084 which is good for either tile or stone.Here is a nice deflection meter:http://www.johnbridge.com/vbulletin/deflecto.plEd, I still think a mud job is the best way to go, but, I am a mud guy and like playing in the mud.That being said, I'd just membrane the ply (Ditra, NobelCS, PVC) and lay your tile. The membrane ought to have fleece on the sides if it is PVC or Nobel--Ditra is an orange waffle type. Whatever. Chevy or Ford.Regards,
Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Thanks for the info. I will be using DalSeal-something, which I learned from John Bridge is a Nobel product made for DalTile. It is orange and fuzzy on both sides.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
DalSeal is fine.Good Luck.Regards,
Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
I will (tapered) rip strips from a 2x8 or 2x10. 16 oc. (is easier to cut few leveling strips from wide lumber with a circular saw.
YCF? Dino