Kerdi Board Mud Extension - Too Much?

[effex80]

Good evening everyone.

To begin, I just want to say I did search for this quite a bit and wasnt able to find a thread that addressed specifically what I was looking for - so here I am posting a new one.

I am doing a Kerdi pre-sloped pan in my basement bathroom remodel, and am working on getting the self leveler poured.

I did my first pour of the entire bathroom with (2) 50 lb bags of "Akona® Self-Leveling Floor Underlayment Cement" from Menards. I got out the 4ft level and sure enough I saw some low spots - maximum being about 1/8th of an inch.

Reading the label on the self leveler it said I can apply another application after 24 hours without needing to prime.

This time, I blocked off where the Kerdi curb will be and poured another 50 lb bag on the pan area.

Come back an hour later and IT STILL HAS LOW SPOTS!!!

Here's my question - Should I wait another 24 hours and try yet another 50 lb bag in the shower area? Should I try to use a different brand of self leveler that might have better flowing qualities? Im concerned there may be adhesion issues if that's the case. Or, should I just get out some mortar and do it by hand?

I am hitting a wall with this bathroom rehab already and I haven't even laid a tile... I have another issue with the drain placement but im going to wait and see what I can find on an existing thread..

Any help is very, very much appreciated.

[Davy]

Thinset mortar isn't designed for this but I've done it many times to fill areas less than 1/4 inch. Force thinset into the low spots and use a straight edge to screed it off. After it sets, rub it down with a rub brick. Vacuum, mop it and check it again.

[jadnashua]

As you've found, SLC doesn't often completely self-level without some help along the way. It's worse when the depth is minimal because of surface tension (think of pouring pancake batter in a pan...it doesn't fill the pan in a thin layer, it stops) and around the edges, you might get a slight curve like what's easy to see with a bead of water on a freshly waxed surface. You have to break the surface tension on the material, and then, sometimes use a smoother to get it to then self-level to a better result.

Some SLC are a bit more fluid than others, but don't use excess water, or it just doesn't work well making for a less than hard result where the sand and cement can separate as well.

[effex80]

@ jadnashua

I tried my best to move it around and work it into corners, clearly I didnt do a good enough job. Id like one of those spiked rollers but I think they are $$$

Do you think I can add another layer of self leveler on top? Its built up about a half inch at this point, so I think I have some room to go before it starts going crazy

I am thinking of getting a better brand from Floor & Decor - any concerns with laying that on top or should I stick to the same brand

[cx]

Welcome, Jack.

I'm not familiar with that brand, but we've heard the same sort of complaint from folks using SLCs of many well known brands over the years. Changing brands is not likely to improve your success, although having tried to install such products several times might.

But let me be the first to recommend you stop fooling with the stuff at all, divest yourself of the foam shower tray, and make your shower floor with deck mud/dry-pack/floor mortar/etc. You'd already have installed your direct bonded waterproofing on that floor by now. Seriously.

My opinion; worth price charged.

[jadnashua]

When I took a class, after the spiked roller, they used a smoother (sort of like a huge float on a pole) to further smooth and flatten the surface. When I used some SLC, I used a snow rake because it had a long handle that let me reach the whole room without walking around in the stuff. Some use spiked shoes to try to stay above the majority of the stuff when working a room.

Another coat if it's recent, probably will work regardless of the brand as the curing process does take some time. But, if it's only a very slight depression, I might seek out something like Ardex's Liquid Backerboard that is designed to be applied in smaller areas rather than flooding the surface. Or, if you have smaller peaks, a rubbing block to rub them down. If it's really slight, while not an approved method, thinset can work. Hassle with that stuff is that it doesn't screed well, as it tends to be sticky.

[jonchicagoland]

How long is that level? The last photo appears from across the internet to be within spec, I'd just want to fix the deeper spot.

Since you have low spots rather than high, I think you'd be better off using a patch product rather than another pour. (at F&D, nxt patch or skim from Laticrete are such products). Read the datasheet, use cold water and expect to move pretty fast. You'll trowel it into the SLC and then screed it off with a straightedge. Doesn't need to be absolutely perfect, just get it to within 1/16" and you're golden.

[effex80]

@ jonchicagoland - its a 4ft level. I would say the largest depression is about 1/8" across 4 feet. Its really only in 2 areas.


@jadnashua This is good advice, thank you!


I might drop another bag in there because after tearing out the sil seal, I noticed it actually worked against me and dammed off the leveler in some areas against the wall. - so there are some rather larger gaps now. Ugh.

@cx I might call around today and try to find a mud man who can help me out. Everyone is so booked out for this stuff. We have a baby due in 4 weeks and really need a functional bathroom!

Thanks everyone - you guys rock! (no pun intended?)

[cx]

Get Mrs. Jack to help. Hell, she got nothing scheduled for a month, eh?

[effex80]

@ CX - Hahaha! Ill run it by her this afternoon.

You may not hear from me again

[redlude97]

Another great patching product is Henry/Ardex feather finish. Doesn't require primer and as the name implies you can blend the edges to a feather. I had to do this with my self leveler as well as I had a couple dips and waves from maybe working the leveler a little past its optimal flow time. It will end up better than trying to pour another layer of self leveler, as most self levelers need to be poured at least 1/8" thick over the previous layer at the highest spot

[Tiger Mountain Tile Inc]

Having a reference for the height of your self-leveling is very helpful too. You don't have to use the special pins they make for slu's but screws or cut up spacers work fine too.

I also think you could buy an inexpensive spiked roller from Amazon and that could help a lot with the thinner pours. Run it over the whole floor for longer than you'd think.

Mixing the slu for the full time called for is a must as well. What are you using to push the leveler around?

[effex80]

Quick help needed here on what my options are.

Our initial plan was to build a small bench from 2x4's and wrap in Kerdi board, waterproof the seams and move on.

I also have the thick kerdi foam I could use to build a bench, but that is quite expensive.

My wife has changed her mind on a built in bench, and would prefer a larger shower base. Is this too much to do a mud extension to the pan?

The plan would be to match the existing slope, then cover with Kerdi membrane with a 2" overlap to the existing pan. From there, do all the corners and seams as normal.

Is this OK to do? I know Kerdi says you can modify the pan size with mud base but Im not sure if they meant nearly a foot.

Thanks,

Jack

[cx]

You could make the entire shower floor with mortar, Jack. Adding more horizontal distance to a foam tray just exacerbates the lack of a level perimeter. Doesn't otherwise change Schluter's recommendations.

You a new papa yet?

[effex80]

LOL you found me again. Yes we had a healthy boy on Dec. 18th!

I actually had a guy come out and quote a mud pan - but he was booked a few months. Couldn't locate anyone else who was willing to just do the pan.

My GC came out set the drain threw the Kerdi pan in this week.

But here I am now I guess I know I know