# Self Leveling Underlayment Nightmare: Help Needed



## Nealtw (Jun 22, 2017)

You said the joists are 22 ft with a wall in the middle or at 12 ft. There is a reason we don't do that anymore. If the floor in one room flexes down the floor in the next room flexes up


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## carpdad (Oct 11, 2010)

https://thefloorpro.com/community/topics/hairline-cracks-in-self-levelling-underlay.6256/


I think, based on this discussion, test for adhesion by sound, if sounds solid enough, patch the dips, fill the cracks with caulk and install your vinyl. Luxury vinyls are thicker, so they may bridge across hairline cracks too, without telegraphing. I used cheaper floating vinyl over less than absolutely flat masonry filler over concrete slab. New vinyls don't show anything beneath. Check with the manufacturer. You should get a straight edge and a level. Box stores have 1x pine. Sight along the edge for a straight line. Check this edge against a plywood edge. All can be done in the store. Then cut the 1x to inch less than 5' and check your current floor. If you must reapply the leveler, screed the leveler and let it settle down. Skip over the toilet flange and trowel over or use the image tool for spreading the compound. I think this tool can be used to push the leveler around as well as breaking the surface tension for easier application? Maybe it limits sticking or breaks the leveler to smaller sections? Guessing, though.


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## Learn2Build (May 28, 2010)

Nealtw said:


> You said the joists are 22 ft with a wall in the middle or at 12 ft. There is a reason we don't do that anymore. If the floor in one room flexes down the floor in the next room flexes up


 No wall. The house is a split level ranch with a finished garage and utility room underneath the bathroom and bedrooms. Beam that stretches the width of the garage, just past the garage door opener.

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## Nealtw (Jun 22, 2017)

Learn2Build said:


> Yes. The house is a split level ranch with a finished garage and utility room underneath the bathroom and bedrooms.
> 
> Sent from my SM-G975U using Tapatalk


Usually the joist don't go full length. But i think the vinyl flooring will be much more forgiving than a tile floor.


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## Learn2Build (May 28, 2010)

carpdad said:


> https://thefloorpro.com/community/topics/hairline-cracks-in-self-levelling-underlay.6256/
> 
> 
> I think, based on this discussion, test for adhesion by sound, if sounds solid enough, patch the dips, fill the cracks with caulk and install your vinyl. Luxury vinyls are thicker, so they may bridge across hairline cracks too, without telegraphing. I used cheaper floating vinyl over less than absolutely flat masonry filler over concrete slab. New vinyls don't show anything beneath. Check with the manufacturer. You should get a straight edge and a level. Box stores have 1x pine. Sight along the edge for a straight line. Check this edge against a plywood edge. All can be done in the store. Then cut the 1x to inch less than 5' and check your current floor. If you must reapply the leveler, screed the leveler and let it settle down. Skip over the toilet flange and trowel over or use the image tool for spreading the compound. I think this tool can be used to push the leveler around as well as breaking the surface tension for easier application? Maybe it limits sticking or breaks the leveler to smaller sections? Guessing, though.


Thanks for replying. I have a 4 ft level and a 6 ft level as well as the 1x6 premium pine board. I have checked for dips and high points. My floor came out fairly level lengthwise along the partition wall which I am okay with a slight pitch. Now lengthwise on the other wall where the vanity and toilet will sit it was not flat, nor did it come out very level width wise I assume because I lost product at those two areas. 

So after being intimidated at the thought of trying to use SLC again, I bought TEC PerfectFinish from Menards to try and level up, build up, or at least get in the same plane when checking with a 5 ft pine board width wise with the room. It was at this time when I was troweling that I started to notice the hairline cracks. The unfortunate circumstance when getting it flat one way it now eliminates the flatness lengthwise. It is making the whole thing worse.

So if I go back to self leveler as you mentioned do I caulk the cracks we concrete crack filler before hand or polyurethane caulk? Also the cracks are so fine I not sure how much I could get in there even with tooling it in. Lastly, I dont want to go thick where it comes out level in all directions, I really just want flat in all directions; do you know if this achievable with SLU at a slight pitch? 
I will have to get pictures When I am back home.
Thanks again.

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## Learn2Build (May 28, 2010)

Nealtw said:


> Usually the joist don't go full length. But i think the vinyl flooring will be much more forgiving than a tile floor.


I can't say with certainty that they are because the garage was finished before my time there. I am basing that on how they ran the floor joists in my great room (main level). They ran the whole width which is either 15 or 16 ft spans of 2"×12" without any beams. I have major floor bounce.

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## Nealtw (Jun 22, 2017)

Learn2Build said:


> I can't say with certainty that they are because the garage was finished before my time there. I am basing that on how they ran the floor joists in my great room (main level). They ran the whole width which is either 15 or 16 ft spans of 2"×12" without any beams. I have major floor bounce.
> 
> Sent from my SM-G975U using Tapatalk


15,16 ft 2x10 is pushing the limit we double up for kitchens, Your 2x12s should have been good


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## carpdad (Oct 11, 2010)

I don't think you have to fill the hairline cracks. I think you could even use thin vinyl sheets and not have any problems. I mention a straight edge to measure from wall to wall, since using 4' level, you're using wrong reference points. This is not to get a level plane. Using the level just as a straight edge. Slight daylight, maybe even 1/32, won't matter because once vinyl is installed, such differences will not be seen. But 1/16 may be felt under feet.

First draw lines on the floor where the vanity will go. This part can be fudged or ignored since vanity bottom is covered with a trim. Even if on legs or floating, legs are adjustable and the vanity itself will cover up the mistakes. I'm talking about slight mistakes that could be seen telegraphed through the flooring. Again, thick flooring covers more, but this is on site call, based somewhat on experience using the material.

Even toilet itself can be shimmed and caulked so again, covering up mistakes. 

So use the straight edge to see where it dips. Slight mounding can be ground and sanded against the straight edge. Dips can be filled in with patches. Homedepot bruce floor patch - trowel for trowel size small area to get a flat surface, but can be feathered to zero. If the straight edge says the entire floor is beyond small grinds and patches, then I assume you need to try the leveler again. This kind of patch is strong even when to a feather thickness, but also very sticky. After troweling to fairly flat plane, wet the trowel and lightly go over the surface to fix the trowel marks, drag marks.


Sorry but I have not used the leveler. I researched it for something else I had in mind - ended up not using it. As such, I don't know how the leveler will act on a sloped surface. You can test on 2x2 ply, pitching it to match your floor. Or go to forums such as pasted above. Johnbridge.com is another forum where pros gather. You need a pro who has come across this kind of situations using a leveler. My guess is that leveler does not act like a water across a wide space, it will not flow from one corner to opposite corner and level itself. But it may across a small area such as 2x2 or 3x3'. This is why the leveler is pushed around with tools. This is somewhat experience. Leveler is pushed around for even distribution and when the "mixing" or pushing around distributes even amount across the whole floor, then the leveler settles itself for flat "surface". It is not as easy or fool proof, I assume.



If leveling again, make sure there is no way for the leveler to leak. Hairline cracks will not need damming I think, but the gaps to the wall, gaps around threshold, gaps around toilet, under the tub or shower(?), all need to be caulked shut. In this case, think of the leveler like water or pancake batter.


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## Learn2Build (May 28, 2010)

Here are pictures. You can see at the vent the crack is all the way through, I assume the rest are as well. There are ones the have carved out a bit and filled in.









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## Learn2Build (May 28, 2010)

carpdad said:


> I don't think you have to fill the hairline cracks. I think you could even use thin vinyl sheets and not have any problems. I mention a straight edge to measure from wall to wall, since using 4' level, you're using wrong reference points. This is not to get a level plane. Using the level just as a straight edge. Slight daylight, maybe even 1/32, won't matter because once vinyl is installed, such differences will not be seen. But 1/16 may be felt under feet.
> 
> First draw lines on the floor where the vanity will go. This part can be fudged or ignored since vanity bottom is covered with a trim. Even if on legs or floating, legs are adjustable and the vanity itself will cover up the mistakes. I'm talking about slight mistakes that could be seen telegraphed through the flooring. Again, thick flooring covers more, but this is on site call, based somewhat on experience using the material.
> 
> ...


 I got a floor installer (a pro) out to look at my situation. He said he wouldn't go any further. Whether it was his job or his own house it would get torn out. It may be bonded well but also could continue to crack, and no telling what it will do in 6 months to a year. 
He suggested busting it up and starting from scratch. He also frowned at TEC Skill Set brand saying it is at the bottom end of quality products. He perfers Mapei or another brand that I never heard of.
I guess that is where I am at. I'll probably do the tear out and pay him to do the rest. Try to save time and money and end up paying twice as much and taking 4 times longer to be done, somethings are beyond DIY. Lesson learned.

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## carpdad (Oct 11, 2010)

Sorry to hear you may be giving up. But I can say that because I have more failures in my history.:smile: Meaning I would usually consider fix options.

But not without some reasons. Leveler is a cement like a driveway or patio concrete. But high strength and high adhesion cement, so the cost. AS such, where is it going to go for the crack to widen? Your leveler is not on shifting ground or slippery gravel. It is contained. Also your vinyl planks are thick enough to bridge some spaces. I'm not trying to insult your contractor, he may be zero deviance kind of guy. But taking first guy's, with self interest, opinion is not what I would do.


I see absolutely nothing wrong with those cracks as far as would they show up through the flooring?. Maybe a photo of the whole floor with 5' straight edge with light behind the edge? Take a straight edge readings every 2- 3". Make a mark where there are equal or more than 1/16. Whole area level or patch could depend on how many marks you have and how steep those dips are.


Base on the discussion (floorpro.com), even the pros can end up with hairline cracks. Guesses why were suggestive but not definitive. Meaning even the pros can have the material run away from them.


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## Learn2Build (May 28, 2010)

carpdad said:


> Soory to hear you may be giving up. But I can say that because I have more failures in my history.[emoji2] Meaning I would usually consider fix options.
> 
> But not without some reasons. Leveler is a cement like a driveway or patio concrete. But high strength and high adhesion cement, so the cost. AS such, where is it going to go for the crack to widen? Your leveler is not on shifting ground or slippery gravel. It is contained. Also your vinyl planks are thick enough to bridge some spaces. I'm not trying to insult your contractor, he may be zero deviance kind of guy. But taking first guy's, with self interest, opinion is not what I would do.
> 
> ...


If I did move forward and did another self leveler application. I am also concerned about using the self leveler over the Perfect Finish feather patching material. I know they are both cement based products but wonder if making it a self leveling sandwich is a recipe for failure?

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## MTN REMODEL LLC (Sep 11, 2010)

I don't know with certainity....BUT

Yes, I would have used lath/screed well stapled over plywood.

Yes, SLC is a good product, but as you experienced will leak very easily, and is not entirely "self-leveling". That roller above looks neat, I use a hard tine rack to assist leveling.

BUT, as the *homeowner, not as a contractor,* I might level any signiicant dips maybe with Ardex which can be featherd or other flooring product. As you note, you used the primer and have a* good bond* to plywood.

And, as you have a small area, and assuming you are not putting your LVT under your cabinets, and assuming you do not have excessive cost for your budget in LVT costs, AS THE HOMEOWNER, I'd go ahead and lay down your LVT.

Seems to me, what do you have to loose really...verse having this contractor redo your underlayment.

One, I think you have a good chance of no problem considering LVT/LVP and a good bond. The spider web does not scare me considering your product.

And if it should fail in the future, not much more difficult to then go back and redo, as it is a small room.

I'd gamble....when I think the odds are in your favor. (That is as the homeowner, not as a contractor).


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## carpdad (Oct 11, 2010)

Again not a pro. But cement is cement. Fresh cement to fresh cement. These are made for adhesion and strength. Prime again and that much more insurance. I would definitely post the photos and the leveler to patch question in pro forums. More heads are better and hopefully the consensus would go your way.:smile:



I think you can definitely benefit from buying a sheet of 1/4" ply and cut 2 straight edges. 6" wide. One 4" shorter than 5', another 4" shorter than 8'. Check for flat plane both ways. Cut a slot to go over the toilet flange. This creates a picture in your mind and a plan of attack. Make sure you use the factory edge.:smile: Sorry for the jokes.


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## carpdad (Oct 11, 2010)

Also, levelers claim not to shrink but from what I read, that is not universal guarantee. Your photos show classic shrink cracks. Maybe some brands are better, and I think your brand was usually the last choice among some pros, but there were some people who used it with good results. I don't think it's the brand. Somethings just happen sometimes.


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## Learn2Build (May 28, 2010)

Whole floor pictures as requested.









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## Learn2Build (May 28, 2010)

MTN REMODEL LLC said:


> I don't know with certainity....BUT
> 
> 
> 
> ...


I do plan on putting LVT under the vanity cabinet (42"×22" with an open bottom on legs) as well as under the toilet. I would need to glue those planks down.

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## carpdad (Oct 11, 2010)

I can't see what the floor is like from those photos. Need low angle photos with a straight edge as a reference. I think I see little missing slc near the toilet flange and trowel mark also near it? Little missing, I think, will be covered by the toilet. The trowel mark could be scraped with simple paint scraper. All depends on working with a straight edge.


If you're going to level the whole thing, definitely need to seal against the pvc pipes and the doorway. Tape over the whole toilet flange. Set up 1x1 dam around the duct hole. Tape cover the duct hole first. The register cover will be at least 1" bigger than the hole. By covering the holes, you can work quickly without worrying about spilling into them. SLC also is quick setting so you can't take too much time mixing and applying. I didn't read the slc manual but using chilly water may help. Read the manual. It may actually say don't use chilly water. Prepare measuring containers and use accurate amount of the compound to water. I read in that floorpro discussion that the mixing speed should be 1200 rpm. My drill says it is 0-1200 rpm. Search for proper type of mixing paddle. Water in the mixing bucket first, start the drill and add the powder in small amounts. This order as not to burn out the drill. Starting with a dry mix may. Have the proper amount of the slc in a bucket. Don't measure out of the bag.



I don't think you have to glue the tiles around the toilet or the vanity. Let it float. The area is small enough that rest of the tiles will move without opening up joints, I think. The open joint problem comes from many tile joints adding up over a large area.


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## Learn2Build (May 28, 2010)

My drill says 850 Max RPM at no load. The bag wants it mixed at 650 RPM for 3 minutes. But at this point I think I will keep trying to feather it in since it's getting really close. There is still more fill and feather work needed in the general area around the flange as well as lengthwise at far end of toilet flange. But there are also a few slightly high spots that need sanded down before anything gets filled or feathered.

As far as the LVP, I didn't want to glue it, especially in my current situation but the instructions say to do it. It was reaffirmed when I talked to Shaw Flooring support and said it needed to done. What I don't understand why only those planks need to be glued but the rest of the room is okay to float. I think that could cause some seperation issues down the road. But then again I am no engineer. Usually pretty good at following directions when my reading comprehension is on point.

I put a post over at TheFloorPro
Anyway, I am getting ready to go out of town for work this week so virtually no progress will be made. I truly appreciate your help as well as everyone's elses input thus far.

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## Learn2Build (May 28, 2010)

So I was double checking my high spots. All my high spots are where the floor has cracked. This includes the cracks that weren't carved out and filled. So I have a fair number of them. Is it normal for hairline cracks from shrinkage to act this way, or is it something worse?









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## carpdad (Oct 11, 2010)

Appreciate you sticking with this thread. Learning a lot about the slc myself. But more reading is not ending up with definitive answer. Your tile guy may be was right, although his short answer probably came from his experience with failed diy home owners.:smile:
I quickly read mapei and tec ez manuals. Also:




https://www.johnbridge.com/vbulletin/showthread.php?t=44325&page=2


https://www.diychatroom.com/f19/self-leveling-cracking-normal-176130/


https://www.johnbridge.com/vbulletin/archive/index.php/t-122896.html


https://diy.stackexchange.com/quest...d-to-level-old-thin-set-over-plywood-subfloor


Last link is about slc over old thinset. 3 different confident answers.:smile: This shows that nobody may have definitive answer because slc is still new to the industry, that goes triple for diy-ers. These answers are not about how, but what slc is. 3 different descriptions of one elephant.:smile:



Among all the talk, "lathe" comes up often. That is metal lathe, probably using flat head roofing nails. For wood frame floor, some pros are saying that lathe is a must. Primer alone may still end up with delaminating slc from the wooden floor. But the same people say that if lathe is used, slc should be 3/4" thick. Manuals don't say this. So what if all I need is far less than 3/4"? There is no answer.


I also remembered that cement can curl as it dries (mike haduck - youtube). So, your floor: hairline cracks are fine. But one side may be curling up. That probably means loss of adhesion. If sounding alone is not sure, my guess would be to grind cut a 3-4" piece along the crack, remove it and see if there is some space under the slc.
Another test may be put a block of wood along the crack. Then give the block a good hit and see if new cracks appear in the area. Since you're away and giving the slc more time to cure, hitting it shouldn't just crack the slc.
Another is 6" piece of 3/4 ply or 2x4. Screw this along the crack and see if the floor goes back to flat plane or new cracks appear.


I'm also wondering if your slc was poured as one or in batches and small separate areas. Manuals say that all of the bag must be mixed. Work time for slc is about 15 minutes. Those minutes begin as soon as slc hits the water. Every second you use for anything else is that much time removed from actual application.
My take from all this is that slc needs several people and several mixing containers. When first bag hits the water, there must be secong person mixing second batch. A third person should be waiting for the first batch ready to distribute. As such, slc is one tricky material to work with.
For large area, first batch should be distributed and probably not touched again if 15 minutes have passed. As such, the distributer must have some experience and must have prepared the area for level, dips and bumps.


To summarize, I think you should check the slc to see if it separated from the floor. If not, patch the cut out, prime and pour a repair layer. 



Your tec ez is 5000 psi and good to zero feathering. I think you should continue to use it. In one of those threads above, there was one mention about low density foam around the perimeter. This is so the foam can give to slc expansion. I said that the concrete shrinks, but maybe slc is more like expanding cement? Such as cement plugs that expand to plug up holes in foundation.


I think I'll avoid slc as much as possible, for myself. Or practice on my parent's house.:smile:



If all of this is too unsure for yourself, you could remove the slc. Rental demolition hammer-drill with scraping bit should make it easy enough. Then flatten the floor with plywood or concrete board set in thinset. Predrilled holes, screws and straight edge should give you flat enough surface.


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## Learn2Build (May 28, 2010)

Went ahead and grabbed some scrap wood and gave it a whack nothing appeared. I decided to sand down along the cracks with an orbital sander to get rid of the humps. Had to wet sand since dry sanding just polishes and burnishes the concrete. 
Using a spray bottle to keep the areas wet, I noticed small lines that were drying quickly. They were cracks so small I couldn't see them when dry. I wetted the areas again, grabbed my block of wood, and gave it a rap of the hammer. More lines appeared. So this is where I am at today:









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## carpdad (Oct 11, 2010)

Finally got sick of it, huh?:smile: It looks like there was adhesion problem. Plus the plywood floor bounced. Chalk it away to a learning experience. Also post that photo to other pro forums for more opinions. It's not bad to learn post script.


After geting down to the plywood, consider using 1/4" hardiboard (cement/wood fiber board, smoother and resistant to water). You may want a grinder with a diamond blade to cut around the toilet flange. Masonary drill bit for predrilling screw holes and cheap countersink bit (2-3) for screw heads. Then coat 2x with redguard. Patch over the joints if joints are not even. 

Check your ply floor with a straight edge for how flat it is. You probably wanted absolute flat with slc, but I personally could live with even 1/8 dip in the middle across the width and lengths. Layers cover over small imperfections. Another underlayment and vinyl flooring will make small defects disappear.


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## Learn2Build (May 28, 2010)

Ended up with belt sanding high spots at some of the joints and underlayment after. Turned out nice and any imperfections were unnoticeable as you mentioned. Old thread but appreciated the help.


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