Your comments make me think there are specific reasons that the GC isn't coordinating this?

Well, if the inexperienced GC is only giving you "loose directions", did you at least read this before you proceeded?

Prior to using any slc, you really need your ducks lined up. You need all your prep work done, especially sealing any crevices that the slc could flow through. You need to contain the slc to get a level finished area.

You also need to have your helpers lined up and they need to know their roles in the process. Who is mixing the next batch, who is transporting, who is placing, who is leveling, who is cleaning.

The key to placing slc is to do it in one "continuous" pour, you want to be placing the second batch before the first batch is past its open time.

If the floor is so out of whack that you have an excessive thickness of slc to be placed, then it can either be done in separate lifts, or you can ditch the slc and do a mud floor.

From your post I don't know what the scope of the project is - are you just leveling the area under the shower base, or are you leveling the entire bathroom floor?

Were this my project, and the floor was really nasty, I'd consider pulling the subfloor and leveling the floor joists (new joists sistered to the existing or tapered shims on top of the existing). Presumably it's not too bad since you're going the slc route.

For slc I'd prep the existing floor. Re-nail what's there, and if needed, add another layer of ply.

Then add a rim to contain the slc. Rim the drain so the slc doesn't flow down the drain hole. Seal any cracks in the underlayment/subfloor.

Prime the underlayment/subfloor if required with an slc primer.

If needing several batches and doing this DIY, try to have a 3-person crew. One to mix, one to transport the product from the mixer to the placer and clean the buckets after the product is placed, and a third person to place the slc.

At a minimum you need two people, one to mix, another to place.

You need to be a well-coordinated crew as you don't want cold joints from one batch of slc to another.

As far as placing the terrazzo base, as long as the subfloor is level, the drain holes line up and the area is properly framed, it's not that difficult.

Mongo

Thanks for the reply -- please bear with me!

I see you noted my attempt at diplomacy....

Just to add to my misery, a non-pro over at JB is saying he thinks we shouldn't have installed Hardibacker over plank subflooring (as we were instructed to do), we should have used plywood. Exploding head time.

We are just attempting to level the base area -- room from end to end is fairly level, we just have some very low spots ( ~ 1") at front of base area. We didn't think to check for that, and well, no one else did either.

I'm hoping we're not screwed by *not* getting the area leveled in one go? [we ran out of product, it being 11 pm and all.] We split the bag into 2 (dry) batches, and poured second out pretty quickly after 1st. Maybe not quick enough, though, as I wasn't mixing as he was pouring -- I will follow your advice next go-round. The hope was to do another pour today and end up with a level area.

>Then add a rim to contain the slc. Rim the drain so the slc doesn't flow down the drain hole. Seal any cracks in the underlayment/subfloor.

Rims were done, drain was sealed, self-leveler's accompanying primer was used on Hardibacker. We used plastic under the Hardibacker to contain excess/seepage.

And we did read directions -- hence my waving red flags at Mr Vix's desire to overwater with next bag of 86. He feels to get the self-leveler to self-level it needs to be more liquid, and while I see his point I'm thinking there's a reason for the ratio.

Re the base install -- the crew seems unsure of how to lower and wedge in the 500 lb beast. Additionally, would you rec "back buttering" the base vs putting the mortar down 1st?

TIA

Just a couple of comments. First, concerning the consistency on the SLC, Mongo's right. Read the directions and stick to them religiously!! If you mix it too tight, it won't flow properly, and if you mix it too loose, you'll get cracking, or you'll get a yellow haze on top which will allow the thinset bond to break pretty quickly after the tile's set. When mixed properly, you should still need to help it flow to a point.

Secondly, who ever told you over in John's forum that you need to put plywood down first over the planking? They're right. You CAN NOT lay backerboard down over dimensional lumber, it must be engineered wood products (i.e. plywood, OSB, Advantec, etc.).

Bill, from your text to Mr Vix's ears....

Just to clarify, this is NOT for tile, but for a 500 lb terrazzo base. Don't know if that changes your opinion re what's on top of our seasoned (100+ year old) plank? I know for tile it's absolutely not the done thing!

Thanks to you both.

If it's just for the base, then you just want whatever stops the SLC from running through the planks!

Yes, it's just for the base! We aren't doing a tile floor, just wall tile.

Which I stated on the JB thread but still got the "plank + plywood + SLC ( + mortared-in terrazzo base)" recs from several.

So you and Mongo think I'm good to go as-is? Plank + Hardibacker + SLC + mortar/terrazzo? No SLC ran through last night, so we seem to be safe there.

Please say yes so I can fully breathe for the first time in 2 days....

[Until having to stay on top of the tile-in window and walls, anyway.]

I posted a follow-up earlier this afternoon but had to abandon it mid-sentence. Isn't it terrible when real life interferes with cyber life?

What I wrote earlier was that while yes, your installation is "incorrect", since it'll be sitting under 500 lbs of footprint compression, I'm not terribly worried about the hardie over the planks.

If it were tile I'd tell you to tear it all out and start over.

I also highly recommend that you read the manufacturer's installation instructions for the remaining materials you use.

Most materials have fairly straightforward instruction, but many builder and homeowners often overlook the obvious. There can be incompatibility issues with thinsets, etc, that can lead to problems down the road. Finding out things now will help you help your installers do it right.

A little reading now can save a lot of aggravation later.

Best, Mongo

Thanks, Mongo. Architect buddy got back to me and agrees with you (and Bill, if I've got his rec straight).

And we will definitely double-check the specific type of mortar-to-terrazzo-to-SLC compatibility issue before they put that sucker down.

Guess I know what I'm doing after mixing up SLC...and suggestions taken, of course.

Thanks again for the help in my hour(s) of need.

Don't think Mr Vix and I will be hiring out as concrete experts anytime soon, we -- mostly he -- got it good enough that the terrazzo install went fairly well. Couldn't believe it took a total of 75 lbs of SLC for a ~ 3 x 5 spot!

After two significant, time-wasting screw ups we switched from using an Acorn base to a Creative Industries one -- and it was my bad that I didn't get a sample from the latter or ask about finishing.

So I had to sand down the base to get some random arrived-with blobs and honing marks off, then seal it with 511's Enhance and Seal (still high on life from the fumes drifting through the house!)...but despite the journey I think the terrazzo was a good choice for us and the more matte finish works better with the (future) lino floor.

Someday I may even get to USE the shower!