Self Leveling Concrete Catastrophe

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David Wilson

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So this will be lengthy and detailed but here goes. I’m remodeling a small bathroom (80 sq.ft) and wanted a heated tile floor. My old floor was ripped to the joists which are 2x10’s spaces on 16” centers. I blocked every few feet and screwed down 23/32 subfloor plywood sheathing. I screwed in every 8” with 3 1/2” t-25 screws. It is very level and very solid.
Next, and this is I believe my huge error, I rolled on a basic oil based primer. It was just some stuff I had left over- primer is primer was my reasoning. I then proceeded to caulk all edges and seems with silicone. The primer dried and sat for about 4 days.
I purchased 4 bags (55 lbs each) of SLC from The Tile Shop, which I divided into half to make easier to handle and mix in 5 gallon buckets. They were stamped 9/17 date. Following the instructions verbatim, I mixed the dry SLC into the water using a paddle type bit on a heavy duty drill at low to moderate speed. Each bucket was mixed for 2-3 mins and then remixed just before I poured. The entire process took me 20-30 minutes. The final 2 buckets I added about an additional 1 cup of H20 as it seemed a bit too thick.
The pour went fine. I poured each one into and towards the last. It appeared consistent and smooth. Two areas leaked just a bit into the basement. Very minimal- about a cup or two.
It was dry within 24 hours and I knocked on it and heard that devastating hollow noise. I could also see a small variation in hue from pour to pour. Now that a week has passed I’ve developed several cracks that traverse from edge to edge and intersect like a cobweb. These cracks will move vertically and I’m starting to hear a disgusting crackling noise. So obviously, it’s a catastrophic loss.
I’ll be taking it all up. My questions are: what went wrong? What can I do on the next pour to prevent this issue from happening again. Should I use a different product? Is that date a use by date or a production date? Can I put the appropriate primer over my oil based primer or should I sand it off? My heart can’t take another failure like this. I’m only out $200 with cement and heating coils but worse is the time invested. Luckily I hadn’t put down my marble tiles yet.
Please be as specific as possible.
Thanks
Burned
 

jadnashua

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SLC requires a special, bond enhancing primer...it's not a sealer, and it is best to use the one specified by the manufacturer of the SLC. Also, most of the SLC products over a wooden subflooring require a minimum depth and lath to help reinforce it. WHile most of them can be tapered to a feather edge over say a slab, over a wooden subfloor, they often want a minimum depth of 0.5" above the highest point. There are a few that can be installed without a primer, and will allow use without lath, but not many. When installed with the proper primer at at least the minimum depth, I can tell you from experience that the bond can be quite tenacious. Sounds like yours has debonded. It may be a total loss at this point. You'd have to either cover or remove the existing primer as well, then install a compatible one on a clean surface. You also cannot pour the stuff tight up to rigid surfaces like walls or cabinets...it needs some room to expand and contract. Often, people will use something like foam sill seal (some have adhesive to help hold it in place against the wall)...you can cut off the excess once the SLC has cured.

Depending on the products used, there is often a min/max time between applying the primer and then installing the SLC over it. Some have a fairly short time-window, some allow 24-hours or so. When pouring SLC, you always want to pour from the wet edge out...

SLC does not really self-level! It needs help, and you do not have a lot of time to make that happen. Just like a pancake doesn't flow to fill the pan, SLC doesn't either...it will have a meniscus or bead at the edges unless you move it around. ANd, once it starts to setup, you will never get it flat if it wasn't already. IT's strange stuff that has a learning curve or a lot of careful study before use for a successful end result.
 

David Wilson

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SLC requires a special, bond enhancing primer...it's not a sealer, and it is best to use the one specified by the manufacturer of the SLC. Also, most of the SLC products over a wooden subflooring require a minimum depth and lath to help reinforce it. WHile most of them can be tapered to a feather edge over say a slab, over a wooden subfloor, they often want a minimum depth of 0.5" above the highest point. There are a few that can be installed without a primer, and will allow use without lath, but not many. When installed with the proper primer at at least the minimum depth, I can tell you from experience that the bond can be quite tenacious. Sounds like yours has debonded. It may be a total loss at this point. You'd have to either cover or remove the existing primer as well, then install a compatible one on a clean surface. You also cannot pour the stuff tight up to rigid surfaces like walls or cabinets...it needs some room to expand and contract. Often, people will use something like foam sill seal (some have adhesive to help hold it in place against the wall)...you can cut off the excess once the SLC has cured.

Depending on the products used, there is often a min/max time between applying the primer and then installing the SLC over it. Some have a fairly short time-window, some allow 24-hours or so. When pouring SLC, you always want to pour from the wet edge out...

SLC does not really self-level! It needs help, and you do not have a lot of time to make that happen. Just like a pancake doesn't flow to fill the pan, SLC doesn't either...it will have a meniscus or bead at the edges unless you move it around. ANd, once it starts to setup, you will never get it flat if it wasn't already. IT's strange stuff that has a learning curve or a lot of careful study before use for a successful end result.
Great info! Thanks. When you say cover or remove existing primer, what exactly would you recommend? Can I simply sand it off? I’d rather not add to the floor height. You don’t think the new primer would adhere to my already primed subfloor?
What method do you suggest to move the slc around? Could I use a thick textured paint roller?
Last one, the Tile Store product suggests lathe only if over 1/2” thick. Does this sound ok? Again, I’m reluctant to re-use the product that failed once but if it was all my fault (wrong primer, no foam perimeter) I’d be willing to try again. I’m not super keen on lathing.
 

David Wilson

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I sanded off the oil based primer and then put down the recommended primer. No problems this time.
Use the right stuff!!!
 

jadnashua

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Glad it worked out for you. Sorry, I did not see your questions, or I could have added some additional comments for you.

SLC is a fantastic product, but can end up making a real mess if you don't understand its capability and installation requirements. Unfortunately, it's also expensive, so remedial efforts are both costly and time consuming.
 

David Wilson

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Try posting your request to the general group.
I’m no expert! Moving it around is one way to get it to settle. You could also use a level and draw a line, in the wall, around the perimeter of the room. Say at the 1/2” mark.
You could also buy some cheap levels at harbor freight and float them across the top just after pouring.
Good luck!
 

ScottLarmr051

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So this will be lengthy and detailed but here goes. I’m remodeling a small bathroom (80 sq.ft) and wanted a heated tile floor. My old floor was ripped to the joists which are 2x10’s spaces on 16” centers. I blocked every few feet and screwed down 23/32 subfloor plywood sheathing. I screwed in every 8” with 3 1/2” t-25 screws. It is very level and very solid.
Next, and this is I believe my huge error, I rolled on a basic oil based primer. It was just some stuff I had left over- primer is primer was my reasoning. I then proceeded to caulk all edges and seems with silicone. The primer dried and sat for about 4 days.
I purchased 4 bags (55 lbs each) of SLC from The Tile Shop, which I divided into half to make easier to handle and mix in 5 gallon buckets. They were stamped 9/17 date. Following the instructions verbatim, I mixed the dry SLC into the water using a paddle type bit on a heavy duty drill at low to moderate speed. Each bucket was mixed for 2-3 mins and then remixed just before I poured. The entire process took me 20-30 minutes. The final 2 buckets I added about an additional 1 cup of H20 as it seemed a bit too thick.
The pour went fine. I poured each one into and towards the last. It appeared consistent and smooth. Two areas leaked just a bit into the basement. Very minimal- about a cup or two.
It was dry within 24 hours and I knocked on it and heard that devastating hollow noise. I could also see a small variation in hue from pour to pour. Now that a week has passed I’ve developed several cracks that traverse from edge to edge and intersect like a cobweb. These cracks will move vertically and I’m starting to hear a disgusting crackling noise. So obviously, it’s a catastrophic loss.
I’ll be taking it all up. My questions are floor leveling atlanta: what went wrong? What can I do on the next pour to prevent this issue from happening again. Should I use a different product? Is that date a use by date or a production date? Can I put the appropriate primer over my oil based primer or should I sand it off? My heart can’t take another failure like this. I’m only out $200 with cement and heating coils but worse is the time invested. Luckily I hadn’t put down my marble tiles yet.
Please be as specific as possible.
Thanks
Burned
I had a contractor come in to do some leveling with self leveling compund called Pro Set 200. Unfortunately, this guy over watered the mix and when it dried it left a dusy mess, that just keeps kicking up dust and erroding. I sweep, I mop and it just keeps rubbing off. This is an underlayment leveling for what is going to be a floating floor with a cork sound barrier in between. I cannot glue down this cork in the areas where the defective leveling is taking place. I also cannot shot blast this area up (as the product tech support suggests) due to the noise factor of what that would probably be. Does anyone know of a sealer type product to just get the dust to stay sealed down to the floor. I am desperate for a solution.
 
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