Old home Subfloor

Hello All

So in my kitchen, the tile kept cracking, so I decided to learn how to fix this issue.
The floor is not leveled in the slightest it is an old 1920 home. So far I have taken up some tile and I see the thinset and backerboard.

Throughout some research, I see what is needed to allow the title not to break is a decoupling membrane. Schluter-ditra seems like the product needed to have this ensure tile does not crake in the future.
Please correct me if wrong.

What I planned to do was to remove all tile and the backerboard and add 3/4 obs on top of the subfloor. I know this will not level to the floor but I assume it will give it some more rigidness. I am not too worried about the transition from the kitchen to the living room. I just want it to never crack again and be nice and stiff. Is this the best way to go about this?

​​​​​​​[img]blob:https://messages.google.com/c715735d-55db-447b-b4fd-1bea4a10a073[/img]


Title i have remove so far and lowest spot



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The size and span of joists can also be an issue. If they are too small or span to far the floor will bounce and that's also what can cause tile to fail, decoupling membrane or not. But sounds like you are on the right track.

 

Woot woot, Thank you. That is great to hear I am on track.

so just note: 7/8 in to subfloor (backerboard and thin set and tile)

Doing going forward:
subfloor > 3/4 OSB > thinset > Schluter Ditra 1/8" > thinset > Tile 5/16 thick

~ 1.1875 (1 3/16)

How much higher transaction .3125 (5/16) which honestly is not bad give or take a little
and i go with a nice tile level system I wont have any more lippage like before.

I take all comment, criticism, critique Please enlighten me

XSleeper can you expand on that as what you mean by size and span on floor joist can be an issue.
Floor joist are 16 on center but do span over 20 feet I can see what you me kind of as the length allow the wood to bounce if i am thinking correctly. (I know I am overthinking I'm sorry ) with the addition of the OSB that should prevent such flexing right ?Will Screw and glue down OSB to Subfloor , I know that does not help with leveling for leveling tile wise, I will just build up thinset to have moderate level and tile leveling system should help ensure level





Area under kitchen can see kitchen light from here

Area under kitcchen

 

I would use a premium underlayment like Advantech over plain OSB. Advantech is much stronger and stiffer than OSB and is great at helping stiffen a floor.

You have to look at the size of your floor joists to see if they are sufficient for spanning 20'. There are joist span tables online but 20' is a very long distance to span so I'd want to see 2x12 floor joists at the minimum. Especially since you say your span is "over 20 feet".

 

Pilot Dane Sorry I was incorrect with that statement.
The floor joist span 12 feet long and the joist are I assume 1.5 x 9.5

I misspoken and forgot to joist does not go all the way to the end it meets another joist that then goes to the end.

Are you referring this product :
https://www.lowes.com/pd/AdvanTech-F...4-x-8/50126556

Thank you in advance

 

Just remember, flat and level are not the same thing. And flat is more important.

 

I would not advise you to glue the Advantec to your existing subfloor. Just screw it. Gluing it will destroy your original subfloor (that your walls are built on top of) if someone decides to take it up someday.

 

Will do, will just screw it down.

Thank you all

 

Quick Question for the low spot can I build it up with Roofing Felt

Would you advise this?
with all the tile up the low spot i have seen with my 8 foot level I can pretty much put my whole pinky finger under it.
The Joist them self do no have any deflection when i put the level on the joist I have no rocking but the subfloor just has that low spots.

Is there something else you would advise that i could use to build up the low spots before putting down the OSB?

A lot more tile to go and still have to move cabinets




Thank you in advance

 

Yes, you can use layers of #30 felt to shim minor differences in height before you lay the new subfloor. Some use layers of shingles or 1/8 tempered hardboard to shim (between layers of subfloor) if there are some thicker dips. Typically floor leveller is used for this purpose. You could always go that route too. And any defects that you notice AFTER your put down your Advantec can be fixed with a floor patch / leveller too.

As someone mentioned earlier, you don't "always" have to worry about level. But you do want your floor to be flat. So if there are dips under your level when you lay it down, that is what you want to shim. Or if there are humps where the level rocks back and forth, you usually want to try to sand those high spots down a little to reduce the amount you have to shim.

 

I keep a bucket of "shim material" of different thicknesses. It's flat stuff that doesn't easily compress. VCT tile, tar paper, shingles, plywood, paint stirrers... You can stack shim material up in layers to get the thickness you need and you can even taper it near the edges by using fewer layers.

I like to shim underneath the Advantech. It is very hard to force Advantech down into a dip and can put a lot of strain on the screws trying to hold it down. Shimming underneath allows it to naturally lay flat. And you can still do minor shimming, self leveling if needed on top.