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Old 02-14-2018, 03:32 AM   #16
ONC_ben
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So this project has seen some delays.. Got my CBU thinsetted and screwed into place.

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This picture is before I taped the CBU, but it is now all taped.

Since installing the CBU, I borrowed a 10' aluminum 2x4 bar and a 4 foot level from a buddy that does a lot of concrete work, and checked the floor for level and flatness every one foot on both axes.

The outside walls (in front and on left in this picture) rest on house foundation, and floor is essentially level within a few inches of both walls.

Problem is, it slopes down about 3/8" going from the far wall towards the camera in the picture, and 5/8" from left to right in the picture.

There are some humps and valleys between far wall and camera (joists run left to right,) and I have marked the depth of variations from level every foot in both directions.

I now realize with back of envelope calculations that my 4x 50 Lb. bags of SLC will not level this floor.

The SLC specifies it can be poured up to 1" in single application.

But I am beginning to worry a bit about:

a) the total weight of the amount of SLC I will need to apply to level this floor;

b) the transition from the 3/4" hardwood floor I will install to the edge of tiled kitchen floor.

Only the very edge on the right side of picture is 5/8" from level, the vast majority of the floor is 1/4" or less from level.

But on the right hand side, there will be a strip of 5/8" SLC over the 1/4" durock and i guess about 1/8" of thinset under that..

add another 1/8" of thinset and 5/16" of tile, and total height of floor on right side will be 1 7/16" inch thickness, a difference of 11/16" from the future 3/4" wood flooring.

That is close to a 3/4" difference between height of about 1' strip on right edge of kitchen floor and height of future abutting hardwood flooring.

I can perhaps shim up hardwood floor installation a 1/4" around there, but that still leaves a 1/2" difference.

This space will eventually be occupied by kitchen cabinets up to edge of tile floor, so it wont be a tripping hazard, but I can't think of any way to make it look pretty. Even with a metal edge, the metal will be visible rising above the wood flooring.

So I am stymied what to do.

Would it be feasible for me to rip out a 6" to 8" strip of the durock along the left and far walls, then use SLC to fill that space in and level rest of floor?

That would cut down a tremendous amount of the differential between wood floor and tile on right side of this room. But it would mean pouring SLC partially on plywood subfloor (would need to install lathe) and most of it over the CBU.

Would that result in crack in SLC (and tile) along border between CBU and plywood substrates under SLC ?

I have seen a youtube video of floor installer using sheets of ply to fill in very deep areas of a larger floor before putting in SLC, pointing out that by doing so he saved having to purchase a bunch more bags of SLC. But he doesnt have video of the floor 1 year after installation.

Now that I have access to a 10' aluminum bar, I really would love to just get some mud I can screed in to match the slope of the floor to make it flat instead of flat AND level.

But I just haven't been able to figure out what product I could use to do that.

What to do in this situation?? Please Help!! I need to get this floor done so I can cook again
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Last edited by ONC_ben; 02-14-2018 at 03:41 AM.
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Old 02-14-2018, 08:22 AM   #17
ONC_ben
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Beginning to think;

1) rip out new CBU

2) place 1/4" ply in deepest troughs

3) pour SLC

4) put down Kerdi-Ditra

5) set tile.

Ouch. $ and time lost. Plus additional time and money putting in new substrate.

But better than losing more $ and time removing cracked tiles, CBU and starting all over again? And maybe lesson learned?

Gonna build a Sketchup of floor and crunch some numbers.

Sure would be nice to get some advice from the pros
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Old 02-14-2018, 09:01 AM   #18
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There's no need to get the floor level, you just need it to be flat for tiling. So now that you've surveyed the floor on a 1 foot grid, how far out of flat is it?

Cheers, Wayne
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Old 02-15-2018, 02:11 AM   #19
ONC_ben
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Yes, I do realize I only need flat but not level.

I started this thread because I want to know what products I can use to make it flat. Only advice I've gotten so far is DON'T use thinset.

Someone suggested "flashing compound," which I looked up and found is a rubbery stuff used to waterproof around exterior penetrations, and I don't believe that would be proper material for this application.

I have not found any mortar product that specifies it is appropriate for this use. I know people use thinset to flatten wallls for tile installation, but apparently not appropriate for floors.

The only product I have found that specifies it can be used for floor flattening is SLC. Level *is* flat after all.

As I stated in my initial posts, my problem is house is not level, so using SLC means it will pile up thick at lowest point. I now know lowest point is along border with future wood floor installation, so I have a problem.

If there is something I can screed over the durock to make it flat, but which will not then seek level, I would like to know what it is.

Here are some illustrations showing floor flatness and degree it is out of level.

First flatness. I simply laid a 10' aluminum screeding bar across the 10x10 room every foot (without leveling it) and ran gauges underneath to check for low spots.

The first shows low spots when I ran the bar across floor along the depth of the kitchen, the second shows spots when I ran it across width of kitchen:

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Next, checked floor for level. I laid the bar across the room, put 4-foot level on it, and shimmed up the low edge until bar was level. Then I used gauges to measure between floor and bottom of leveled bar.

First, along the depth of the room:

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I need to do the above measurements again. It was first attempt to measure floor, and I realize it does not fit with the next measurement below, in that the right-hand wall above does not show a drop off to 5/8 inches at the bottom.. I suspect I forgot to measure for level against the wall, or did not make sure my starting point was level with the starting point in the next measurement below.

Keeping that in mind... Here is the data for below level along the width of the room:

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I really do not want to use SLC now that I know how much it will require to do the job, AND because I would end up with a 1 1/2 inch floor at the transition to wood flooring on the right side of the room (lower right in above pictures).

But I don't know what else I can do ??
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Last edited by ONC_ben; 02-15-2018 at 03:22 AM. Reason: Picture mix-up.. same picture posted twice with different names
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Old 02-15-2018, 05:36 AM   #20
ONC_ben
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there are a number of mistakes in the pictures in above post.. the color codes are correct, but some of the text overlays show incorrect measurements for the color coding.. anyway, you get the general idea
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Old 02-15-2018, 10:03 AM   #21
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You need a featheredge cementitious patching compound that is rated to go over concrete board. In the past I have heard Henry's Feather Finish mentioned here, but I haven't checked the spec sheet regarding use over concrete board. There are other similar products.

Cheers, Wayne
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Old 02-15-2018, 03:53 PM   #22
jadnashua
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SLC is such a misnomer!

FWIW, if you look for an SLC that says it has thixotropic characteristics, that would work for you. Those types of products 'flow' when you move them, but stabilize when you stop...IOW, they'll stay where you put them, and indeed, can be used to create a ramp if you wished. It's interesting in where the UK Mapei website specifically lists thixotropic characteristics for this product, it is absent from the US spec sheet, but I think they are the same product! Maybe they think the US user wouldn't understand what thixotropic means...when in doubt, a dictionary can help!

http://www.mapei.com/public/US/produ...nipatch-en.pdf
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Old 02-15-2018, 06:07 PM   #23
ONC_ben
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OK, those are both great suggestions

I had read specs on these and other "patching" compounds, and I kind of came to the conclusion they were intended only for small imperfections, like divots and cracks, not for leveling bigger surface.

Also I had written them off because of max 1/2" thickness... but now, looking at my "flatness" measurements the biggest birdbath I have to deal with is about 5 s.f. of -5/16" depth, so I guess either Henry's Featheredge or Mapei Planipatch will work for this job.

There is a flat area of the floor between two depressed areas, so I can screed the area closest to the far wall, then set up for a second screed along the area adjoining the future wood flooring.

It is strange that the term "thixotropic" mortar seems to exist only in other English speaking countries, but not here in U.S. Mapei makes several of them, including one called "Nivolevel" that can go on twice as thick as Planipatch, but apparently marketed only in Europe and Australia.

OK, gotta do the math and pricing, pick a product, return the SLC to the Borg, and flatten this floor...
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