Self Leveling Underlayments – Achieving Level

Carl says:

This thread is great.I am remodeling my basement and planning to lay tile and laminate. I have a floor drain in the center of one room, along with a clean-out. I am planning to raise the floor drain (cast iron) and clean-out using PVC. It’s not actively used as a drain, and the slop toward the drain/cleanout is too large to lay hard-surface floors (tile/laminate) and I don’t want carpet.
The floor has been painted (likely with some type of concrete paint. Is it absolutely necessary to remove the paint? Shouldn’t the primer eliminate the concern about delamination? How would I remove so much paint? The area is prob. 75 sq. feet. Any other advice?

Thanks!

Garth Wood says:

Carl:

You could try what my wife and I have been doing. She got the idea to loosen the paint on the concrete by laying a damp cloth/towel over the areas she wanted to scrape. After a few hours, the moisture goes through the paint and weakens it considerably, allowing it to be taken off by a variety of mechanical techniques. (No dust, either.)

When I saw how well that worked, I said to her “Your steamer would probably work on it too.” She got a light in her eyes and she was off to the races. 😉

And we did finally do a pour of SLC (Mapei) for our new basement bathroom — five bags at $50.00 CDN per bag, all mixed and poured in just under ten minutes. We were flying! It worked so well, when I went to level a cabinet I’d installed later, the side-to-side needed no leveling at all, while the front-to-back was out by a sixteenth of an inch. I leveled it front-to-back just for the Hell of it, but it’s unlikely that I even needed to. Certainly, the pro countertop installers we hired thought it was well within spec without leveling.

Steppenwulf says:

Hi all, this is definitely a helpful chat! But I am wondering…I read somewhere else online that I should use expansion tape around the perimeter of the room (basement bathroom) that I want to level to allow for expansion. Is this really necessary? Does it depend on what material the SLC will contact at the edges (for instance a concrete wall vs. drywall on studs)? Thanks in advance!

Carl says:

Hey all,
Just reporting back on my self-leveling work. Everything went successfully, although the prep work was very time-consuming. I had paint on the floor that needed to be removed. I rented two different pieces of equipment and both failed miserably. I ended up using my 4.5″ angle grinder with the diamond grinding cup to remove the paint. It was really messy.
I ended up putting down 6 bags of LevelQuick RS in three different pours to eliminate the dip that went to my unused basement floor drain. The dip tapered to about 3 inches at the drain. Figuring out how to raise the nearby drain cleanout was also a big chore, but solved through cutting various PVC pieces to accomplish the goal. Thanks much everyone for your help. It was worth the time and expense, in the end.

Steppenwulf says:

Thanks Garth, sounds good! Didn’t think of caulking at the joint of cement and tape, but makes good sense. Went down and pulled up the 80’s sticky tiles on the basement bathroom floor today and found that I have a moisture problem (this was suspected since we found termites down there this past summer–treated in July). Now’s a good chance to mention I have a 1920’s row home. Any ideas about how to handle the moisture? I’m planning on ripping out the studs and drywall attached to the back (poured concrete) wall and painting with the waterproofing basement paint. Can I/should I do this on the floor too? Thanks so much for the advice!

Garth Wood says:

I’m not a fan of metal studs in basements, *particularly* if you’re aware of a pre-existing moisture problem — metal may not support mold/mildew growth, but man oh man can it rust. Your metal studs could easily fall apart in four to five years. (Although I think they’re a good idea for building bulkheads around HVAC components. Light, straight and strong.)

Better, in my opinion, to use pressure-treated wood — certainly for the sill plate (what Carl called the “toe-plate”); that’s what I’m doing in my basement reno, and if you’re concerned about the vertical studs, then for them too; although where I live (Alberta, Canada) it’s building code to keep all studs at least one-half inch away from the concrete wall of a basement, unless the entire wall up to grade has been treated with waterproofing paint (and even then, most of the contractors I’ve talked to still keep the studs away from the concrete). Also helps prevent your insulation (if you’re using fiberglass or rock wool) from wicking moisture. It should also be mentioned that, if you’re using treated lumber, you’re going to need proper fasteners (deck screws designed for pressure-treated lumber, ferinstance), otherwise the chemicals in the studs will eat the fasteners in a few years…

Steppenwulf, when you say “moisture problem,” what *exactly* do you mean? Is there standing water? Is the concrete simply cold and clammy feeling? If the latter, tape a piece of plastic down on that concrete for a day (a one-foot-square should be fine) and then come back and inspect it. Is there condensation? If so, that problem really REALLY needs to be addressed in some fashion before you proceed — otherwise, moisture will just wreck all your good work. It’s astounding how destructive moisture is. A good rule of thumb is: if the relative humidity next to the slab is above 40% or so, untreated wood will definitely start to get dry-rot or some other related problem within a few months or years. Below 40%, and you’re generally good to go. Consider using a product like Dricore, which helps to isolate the concrete floor and its humidity from the flooring above the Dricore (and will also, to a certain extent, provide channeling/isolation for small amounts of standing water should it happen to weep through your concrete floor). Here in Canada, Dricore’s available at Home Depot, and a competitive clone’s available at Rona.

My basement reno’s proceeding after five years of waiting because we finally managed to wrestle our moisture problems to the ground (spending around forty grand to fix it didn’t hurt, either). I wanted to go earlier, but the consulting engineers and general contractors we talked to who had experience with these problems simply said that, if I didn’t solve the moisture problem, I was going to be throwing my money away on a reno. They were right.

Carl says:

Phew, the Red Head sleeve anchors I used are made of stainless steel, so no rusting…

Garth Wood says:

Oh yeah, almost forgot — you can also use PL400 to glue sill plates to the floor. This method assumes that you haven’t got any moisture issues. You have to get the positioning of the plates *exactly* right, ’cause there’s no second chances with PL400. But PL400’s solved several tricky issues for me in my basement.

Garth Wood says:

Scrape it up now, and then use a new bag to pour the stuff. Mix the whole bag with the recommended amount of water — remember, the ingredients in the bag may not be thoroughly mixed in their dry state because of the method used to fill the bag (ingredients may have been dumped in in a sequence instead of thoroughly mixed from one big batcher). As well, the mixing paddle at my Home Depot was a massive ten bucks, and is a wise investment. If you can’t use the whole mixed bag in one spot, either leave it in the bucket to harden (and then dispose of it) or pre-plan to use it elsewhere where you may have some low spots you’ve always been meaning to fix, but never got around to. Once mixed, you’ve got about ten minutes max, and actually quite a bit less if you plan on getting gravity to do all the work.

Temperature isn’t a big deal — cementitious compounds create exothermic (heat-generating) reactions when mixed with water. There are operating temperature ranges for the pour that’ll be specified on the bag of mix, but it doesn’t sound like you went outside them.

Finally, don’t forget to prep the underlying surface as specified in the directions, otherwise your pour will eventually separate from that surface and start flaking (or chunking!) away.

Good luck.

Garth

Garth Wood says:

That doesn’t appear to be the correct mixer paddle — the one you linked to appears to have a “pitch” to the blades which could incorporate large amounts of air into the mix, because it acts like a propeller blade or a screw. Too many air bubbles in the mix can make the final cement weaker, just like adding too much water (though the flooring pros I’ve talked claim they routinely “overwater” their SLC compound by a couple of percent, to allow for easier leveling via gravity).

You need a mixing paddle more like the QEP Super Mixer, which looks like one of the two blades you normally see on a hand mixer for making mashed (whipped) potatoes (although much larger and sturdier, of course). It still incorporates some air, but much less, making the cement stronger. The one you linked to looks like the kind used to mix drywall joint compound. DO NOT OVERMIX — if the instructions say mix for two minutes, get your spouse or someone to actually time it while you’re mixing. It will start to set up even while you’re mixing it if you wait too long. You’re gonna need the extra minutes afterwards to get gravity to do its magic, so stop when the instructions say stop and get pouring. 😉

Once done, you should be able to walk on the surface within a couple of hours, even if it’s fairly cool. I waited overnight, but by next morning, it was quite solid. It continues to get stronger for about the next 30 days, but supposedly achieves most of its ultimate strength within 72 hours.

Finally, yes, you need to re-prep the surface. You don’t need to remove the old polymer coat — just put a new one right over top of it. It should still be slightly tacky when you pour the new SLC on top of it (though the directions claim it can be as old as 24 hours).

Garth

Ken Kipler says:

Good afternoon everyone,

Wow…what a great site. So much helpful information. I have a question I hope someone can help me with. I am putting in a heated floor but I am not using a mat. I placed strips down and weaved the heating element at 2″ intervals. The squeegee suggestion is going to work awesome here…great idea! The problem I have is that I did not prime the floor before I pt down the hearting element. I have not done the pour yet so I can still prime the floor. My qusetion is can I use a roller and prime over the heating elements or would it be better to use a paint brush and prime in between the elements.
Another question is would one person (me) have enough time to mix two buckets of SLC before it started to set in the bucket?
Last question…is there an easy way or appauratus that prevents the mortar from flowing into the heat register?
Thanks for any info you can provide. Ken Kipler

Ken Kipler says:

Thanks for the help Damoni just finished putting on the primer. I will wait a couple of hours then it’s pour time! Kind of nervous though. My son is home so he is going to help me mix the SLC. That sould go pretty smooth. I will let you know how it comes out.

Would like to hear about the hangover story sometime.

Thanks again

Garth Wood says:

Ken, the instructions should tell you (or you can go to the manufacturer’s website and download their white paper on installation), but usually you’re supposed to re-prime freshly-poured SLC if you’re pouring another layer, otherwise the topmost layer can “peel”/flake off. The bag directions should also give you some guidance on how long before you can tile, or again, the manufacturer’s website. Most SLC attains the vast majority of its compressive strength after 72 hours, but can continue to cure for 30 days and (like all cement) can get marginally stronger for many years. That’s why drilling through old concrete’s so much harder than drilling through young stuff. 😉

By the way, the second layer you’re pouring probably won’t level quite as well as the first (thicker) level you’ve just poured, so you’re gonna have to use a trowel (or similar) to feather it out around its edges. Work fast, and fight the temptation to overwork it. At most, you’ve got mebbe ten minutes. You can increase your working time a bit by using ice water in the mix.

Garth Wood says:

You *can* grind down the high spots, but it’s dusty, dirty work. I had to do it once on a small area. If you’re going to do the same, start sooner rather than later, as the SLC’s still relatively “soft” right now. (If it’s a really small area, you might even be able to do it by hand, which would cut down on the flying dust…)

As for the bubbles — I’d have to see ’em, but I suspect that if they’re relatively small and mostly at the surface, your thinset (when you lay down tile) will probably fill them and give them additional strength. I don’t think I’d worry about them too much.

Garth

Dave says:

Fred:
Not sure this thread is still monitored – it’s been a while since the last post. Your video and comments (and the other comments posted) regarding SLUs were tremendously helpful but I have a project that is going to force me to break some of the rules (like going over existing tile) Project is a 10’x18’ concrete slab with a glass greenhouse room. The old room was leaking and had a non-functioning 6’x6’ hot tub. I took the room down, removed the tub and backfilled the hole with gravel topping it off with about 4” of concrete set in with rebar drilled into the existing slab. My plan was to then remove the old tile but I ran out of time (only have about 8’x9’ clean) before the glazers put up the new room. The rotary hammer is not an option now – flying shards of tile and glass don’t play well together…
Can I use an SLU/C to build up the half of the floor that is down to the concrete or am I better off using mortar/thin set? I only need about 1/4” to level up to the remaining tile. On the outside edge, can I use expansion tape to as a boundary? Unlike the basements or gutted bathrooms, etc where most folks here have sued this, I have a “finished” wall that I’d like to protect from free flowing SLU
Is it possible (I know it’s not recommended) to tile over the existing floor? Am I better off going with a second pour for a fresh base for all of the tile (in other words, is there any way to use the SLU over tile – will it adhere if I belt sand the finish off the old tile? I have about a 2” drop at the room threshold so any build-up would be fine (maybe even a bonus)
Hopefully you or Damon or anyone who stumbles across this has run into something similar and will have some advice –
Many thanks!
-Dave

carl says:

You will want it as flat as possible..try using a floor squeegee attached to a broom handle to spread it out. you may want to.consider two pours to make sure its all flat. you can also use a straight 2×4 and rake it across to get it flat. if not flat in all directions you will have hollow areas.

Tina says:

Easy question?: we have one coat of UltraPlan 1 Plus down (14 hours ago) and we need to follow up with another layer. Do we need to prime it before proceeding? Thanks for responses!!!

Tina says:

Thanks for the reply Garth! The package doesn’t give any guidance and the Mepei tech line was hopeless. I finally found two other leveling product’s spec sheets online that suggested doing it so I did!!

Clay says:

Very helpful comments and advice. My question is a slightly different one.

I have a 12′ x 28′ basement room, concrete, unfinished. Using a laser level, I determined that the height of the floor—at the perimeter at least—had an overall variation in height of 1 inch. This difference in height was across the 12 ft shorter dimension, rather than the longer dimension. I went to the big box store and they suggested I use mortar or quikrete for a rough-in, and then followup with the SLC. Problem is with such a large area , I quickly lose sight of what is level away from the walls. I also know that a good part of the floor is an inch low, and the rise comes near to the highest point of the floor, so I would use a lot of SLC.

So my questions are:

1) Is there a way to use the quikrete/mortar as a first step? If so, how do I do this, considering that I will be transitioning from say 3/4″ to 0″?

2) If you recommend using just SLC, do I need to segment the room given its size? And then, how do I address the seams?

ryan delaney says:

Fred,
Do you have to lay a barrier around the walls when applying the self-leveler?

Ryan

Dave says:

Mike:
I did 180′ sq with just my wife and I. I know that most of what you read does not suggest this as the best option but as is often the case, I had no other option. We did not need a 1/2″ so I only used 10 bags but I think if I had 12 bags I would have used them. My floor was less level than I thought. I was using the product to deal with some pocks as you are and also because I had two different materials (a hot tub was removed and back-filled. That slab was about 1/4″ off from the surrounding floor. All we did was mix all of the buckets (bags) at once – I premeasured the water and I poured the bags one at a time as my wife held the drill – went smoother than I anticipated. I also used a cordless drill which everyone says is a no-no. My corded hammer drill (which is ½”) would not accept any of the paddles I tried. So I charged up 4 batteries and started…(never even finished the first battery but I would still make sure you have lots of back-ups if you go the cordless route b/c once you start you’re committed and the stuff isn’t cheap – wouldn’t want to waste it)

To spread it around I used my plastic leaf rake – upside down so I would not catch any of my heat wires – I also hot-glued the heat down – the duct-tape just wouldn’t hold once the cement started going down – at least that was my fear and those few areas around the thermostat where I was afraid to use the hot glue it peeled up – what a mess I would have had if I took the mfg’s advice and used tape….

One caution – if you do go with the “stages approach” be careful how you “dam” the intermediate transitions. I had an outside edge that had a drop-off and I tried using the tallest foam weather-stripping I could find. In a couple areas before it found its level it went over my dam. A couple of spots it also went under and I would imagine using a wood dam would create problems unless it was secured down and sealed along the bottom edge – otherwise the wood might float up and that would be a mess.

Final note- I did call the people that make level-quick (sp?) and there were very helpful in telling me the appropriate specs to calculate how many bags I needed – just, like I said, buy extra – especially if you get it from a HD or someplace where you can return extra. I planned to use 8 and ended up mixing all 10 and like I said, if I had 2-3 more, I would have used them. If I only had the 8 I would have been stuck trying another pour.

Good luck

Fred says:

Fanley, I noticed nobody responded to your comment here and I had hoped someone might. Unfortunately, we don’t have any experience with this. One reader had successfully primed and painted (I believe with some type of epoxy coat) and used it as a wear surface. Quickrete’s leveling product actually notes that this is OK, but I’m fairly certain that LevelQuik doesn’t endorse the method.

James says:

Guys .Thank you very much for the advise. I will update later as the pour commences.

Rob says:

I need a product that is lite weight (with spec’s to show for approval, around 2 1/2lbs per square foot) to cover a floor of 2800 square feet at 1/2 inch thick. A self leveler product that sets enough in a day or two to put carpeting and or tile over it. I am willing to drive to pick up anywhere in the NJ., DE., Pa. NY. area. Products that work are Ardex LP 65, or Prospeck LW 60 which no one seems to have. If you can advise me on anyone that has these products or of and equivlent I would be great full. I need this right away. Thanks

Howard says:

I have a commercial warehouse of about 8,000 square feet. The building is quite old
and the floors are cracked in some areas and have dropped in others. The floor settling seems to have stopped. We have a tenant that wants to run forklifts in the space and has asked us to renovate the floors. Is their a treatment that will stand up to heavy use other than cutting out the old concrete, installing gravel and re-bar then pouring new concrete? If so are there professional installers that work with the product.? Thank you, Howard

Agostinho Carreiro says:

Hi, I just gutted my basement back down to a complete large cement room. Among all the work being done down there to turn it into a livable basement I would like to level the concrete flooring. My question is, should all my stud walls be put up before self leveling the floor or should the whole basement be leveled before the walls are put up. Please email me with the answer or some suggestions. Thank you

Muriel Leko says:

We used Ez leveler on our basement floor and apparently some accidentally went down the drain. We thought we got it all but now the drain is plugged. This is the drain for the runoff from the furnace and air conditioner. Any help would be appreciated!

Amanda says:

Help! I have a half bath that had the old tile thin-set directly to plywood over the subfloor. Once the tile was removed, I attempted to remove the plywood by removing the screws but discovered it is also liquid-nailed to the subfloor. There is still some thinset on this plywood (that I have since re-screwed back in). floor is also slightly uneven in one corner. Advice from HD was to use self leveler over the plywood, then put backerboard on top of that. My issue is that yes, I can thinset backerboard down, if I use leveler UNDER the backerboard, I cant screw the backerboard down to floor. I primed the plywood for leveler, but Im just uneasy as to the next step. Someone has suggested I just use self leveler over the plywood and tile directly to that. As a result of the plywood, then leveler, then backerboard, THEN my tile, my small bathroom floor with be a bit higher than the abutting floor in the hallway. Just want to do it right, but not sure what the best fix is for my issue. Any help will be appreciated! Thanks so much, Amanda

Randy Ellis says:

Can I use this over grace ht ice and water shield? I am using ice and water shield for waterproofing on a porch prior to decking with water proof deck product. I have a few small spots that I would like to level and the water shield has been installed.