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Old 07-28-2014, 12:38 AM   #1
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Help! Need to remove uneven self-leveling compound from backerboard


Hi, I need help...

In attempting to level out unevenly applied Hardi-backer (1/4" hills and valleys) on our bathroom floor (5' x 12'), we did our research and decided to go with self-leveler. On the Internet we were advised to use a primer over the backer board prior to pouring the leveler, so we requested to buy primer at several different hardware stores. But... each time we requested it (and between my husband and myself we ended up speaking to about half a dozen people at 3 different hardware stores) we were told we don't need primer, just go ahead and pour self-leveling compound straight over the Hardi-backer. I guess my first mistake was not to go with my gut to ignore what they all said, and just prime the damn floor.

Anyway, long story short, we poured the self-leveler this morning over unprimed backer board and it immediately started solidifying without leveling out. I saw what seemed to be imminent doom approaching but (and this was my fatal mistake) I didn't have the heart to ask my husband if we could scrape it off--while it was still not set--and start over, as we had already gone through 2 prior batches of self-leveler that came out lumpy and weird and had to be scraped off; I guess I was hoping, or deluding myself, that this time it would actually level out as it set because the consistency at least looked good. Well of course not. We now have self-leveler that is between 1/8 and 1/2 inch thick with stripes and canals going all over the place. Clearly we need to scrape it all off and re-level, or just lay the tile on the Hardibacker without bothering to level.

Thus my questions are:

1) What is the best way to remove self-leveling compound off of Hardi-backer (if that is possible)? As an FYI we have 1/4 in plywood under the Hardi-backer, and the ply is screwed onto solid 2x6 lumber--this is a house built in 1950 and it really has good bones.

2) Once we hopefully are able to remove the self-leveler, what should we do? Prime the surface and try the self-leveler one more time? Or just try to adjust the tiles with back-buttering the tiles with thinset (mortar) to various thicknesses, and doing our best to achieve a flat surface--using a level or something?

By the way, it is likely that I will be the one who will have to do the bulk of the work removing the leveler, as my husband is having to spend a lot of extra hours at his job. I'm a pretty big/"husky" reasonably strong gal, but I probably will need a tool that is 30lbs tops, or I probably won't be able to continue working with it for very long. We've seen some Makita pneumatic hammers that seem somewhat promising and if anyone has any experience it would be wonderful if you could share.



Thank you!
HaywardGal


Last edited by HaywardGal; 07-28-2014 at 12:38 AM. Reason: Forgot to include size of bathroom
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Old 07-28-2014, 05:39 AM   #2
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Help! Need to remove uneven self-leveling compound from backerboard


You have a couple of issues---

I feel bad telling you this--but the 1/4" underlayment is to thin--1/2" BC exterior glue is the proper thing---the dimensional lumber (2x6) move,cup and flatten with changes in humidity---1/4" will not isolate the movement very well.

A question about the cement backer board---did you set that into a bed of wet thinset before you nailed or screwed it down?

Next---the self leveler---that product is soft and easy enough to sand or grind down the high spots---most tile setters use a diamond cup grinder on an angle grinder--

A 36 grit sanding disk will also work.

If the self leveler bonded to the cement board,you should be all right.

How big is the area? Would removing the board be an option? If not--this will be a risky installation.

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Old 07-28-2014, 07:25 AM   #3
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Help! Need to remove uneven self-leveling compound from backerboard


Just a note to all--read the instructions---call the technical help line for the manufacturer when you need confirmation----

A store clerk is seldom a good place to get spot on information---if they knew how to install tile--I bet they would not be a store clerk--

I was at a large tile store last week and asked what bridge saws they had for sale--
Three salesmen--not one of them knew what a bridge saw was---
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Old 07-28-2014, 08:42 AM   #4
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Help! Need to remove uneven self-leveling compound from backerboard


Hi Mike, thank you for the quick reply. I've added my location to my profile now.

Bummer about the 1/4" being too thin... sounds like we likely need to remove everything down to the 2x6 then right? No use building on top of a shaky foundation. Anyway here's how we got to where we are:

The 1/4" plywood was screwed down, I think with sheet rock screws.

We troweled the thinset mortar onto the back of the Hardi-backer with a tool--I can't remember what it's called, my husband knows--that's flat, metal, has a handle, and has 1/4" square teeth on it. I think it's a pretty standard tool for applying mortar to tile etc. Anyway the backer board was screwed into the wood with the recommended screws that are sold along with the Hardi-backer, e.g. specific to that application, and when drilled it went through not only the backer and the thinset and the 1/4" plywood, but also a little bit into the 2x6 lumber underneath. So removing the plywood would involve dealing with both the Hardi-backer screws and the screws used to attach the plywood to the 2x6s... somehow... Ugh I don't even want to think about that.

When we put down the Hardi-backer, we had a lot of problems drilling through, broke tons of bits and so forth. The result was that the Hardi-backer did not get applied evenly flat. We're guessing the thinset got mashed down more in some places than others as we screwed down on the board? Anyway when we put a level on the floor with the backer on it, it tilted this way and that about 1/4" (and this across the short dimension in a 5-ft by 12-ft bathroom). From what we could read, it sounded (and looked, if you saw the floor) like we needed to level or else the tile floor would have rolling waves. Thus began our horrible saga with the self-leveler.

Hayward, California is across the Bay from San Francisco. The weather here is fairly dry and it's been in the 80's lately but in the mornings it's about 55-60F. I'd say at the time we applied the leveler it was about 70F.

Anyway... does this give you enough information for additional insights? I think the lesson is to contract out floor work, as just thinking about all the work that will need to be done to remove everything and start over is exhausting...
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Old 07-28-2014, 11:12 AM   #5
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Help! Need to remove uneven self-leveling compound from backerboard


I'm sorry to say this as well, but Mike is right. You just have a mess there.

Sheet rock screws are not really appropriate - decking screws should be used for plywood - but that isn't your real problem. Also, it's best that you screw the Hardibacker into the plywood, not through into the joists. Therefore the proper screw length depends on the thickness of your subfloor.

Your real problem starts with insufficient subfloor. I know you are saying the house has "good bones", but 2x6 lumber is not really considered solid enough to even start with nowadays. You will have to do some research about what joists are usable for which span lengths of floor. If you start with weak framing, there's not much you can do to fix it.

Assuming the floor joists are OK (either the 2x6 joists spaced close enough together and over a short enough span, or new or sistered joists), then the next step is getting a solid enough subfloor. Most people prefer 3/4" plywood or OSB, with 1/2" plywood on top of that for 1 1/4" total. Hardibacker instructions specify a minimum of 5/8" plywood or 3/4" OSB, and most of us would like to see a little more than that. But the main thing is the L/360 deflection they specify (and which is standard in the tile industry). That really trumps everything, but the thicknesses we are recommending will probably get you there.

1) But in the meantime, your issue is going to be getting that Hardibacker/leveler up. Since the Hardibacker is screwed and the screws are all covered with leveler, you have a mess on your hands. You could use a multitool with a scraper blade, or a demo hammer (http://www.harborfreight.com/power-t...8148-8068.html), or perhaps a Spyder scraper on your reciprocating saw (http://www.spyderproducts.com/toolpages/spyder-scraper/) to remove the leveler.

2) Then you need to search for the screw heads, gouge out the leveler from the heads, and unscrew them. (If anyone knows a faster way to do this, I'm open to suggestions.)

3) After that scrape up the thinset from the plywood subfloor, and search for the screws for that, and get that up.

4) Evaluate the joist situation and reinstall subfloor.

An alternative to 3) is evaluating the joist situation from a crawlspace or basement, and then just adding another 3/4" to 1" of plywood on top of the existing 1/4" and going for your L/360 deflection standard from there.
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Old 07-28-2014, 11:18 AM   #6
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Help! Need to remove uneven self-leveling compound from backerboard


I like Mapei products (there are other good ones), but here is a link to their self-leveling primer line.
http://www.mapei.com/public/US/lined...terials_EN.pdf
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Old 07-28-2014, 11:21 AM   #7
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Help! Need to remove uneven self-leveling compound from backerboard


Quote:
Originally Posted by HaywardGal View Post
We troweled the thinset mortar onto the back of the Hardi-backer with a tool--I can't remember what it's called, my husband knows--that's flat, metal, has a handle, and has 1/4" square teeth on it. I think it's a pretty standard tool for applying mortar to tile etc.
It's called a trowel, and there are many sizes depending on the application. It just so happens that Hardie recommends a 1/4" trowel for installing Hardibacker, so you are good there. Your trowel size for your final tile installation may be different depending (mostly) on the size of the tile, so research the recommended trowel size for your tile before installing.
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Old 07-28-2014, 11:34 AM   #8
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Help! Need to remove uneven self-leveling compound from backerboard


I've been there on the "not priming" issue - it's a nightmare.

As other people have noted, your first problem is really the sub floor. Here's what I would do... get a cheap 3 inch hole bit for your drill and cut out a circle. The self leveler will ruin the bit, so don't use a good one. Once you have a "core" out, use a coat hanger to find the two closest joists. Now, use a circular saw to cut near both joists, effectively cutting a "strip" out of your floor. Get a saw blade that is made for cutting cement. It will be very dusty, dirty work. Next, use a reciprocating saw to cut the screws that are attaching the plywood and cement board to the joists. Now, use the circular saw to cut along the next joist, so you can lift out another strip of plywood/cement board/ self leveling. Repeat until all of the floor is gone.

Alternately, use a magnet to locate screws, then dig them out with a cold chisel and hammer, then unscrew the cement board from the plywood. Then do the same thing to find the screws that are attaching the plywood to the joists.

I feel for you!!!
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Old 07-28-2014, 11:43 AM   #9
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Help! Need to remove uneven self-leveling compound from backerboard


The floor cutting would work, but as said is extremely tedious and dusty. I like the magnet idea, which could eliminate the need to remove the leveler. You could use this
http://www.globalindustrial.com/p/to...Q&gclsrc=aw.ds

Or even try an app
https://play.google.com/store/apps/d...udfinder&hl=en
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Old 07-28-2014, 02:13 PM   #10
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Help! Need to remove uneven self-leveling compound from backerboard


Hello All,

Thank you so much for your kind responses!

Just one clarification--the 1/4" plywood was just meant to be a smooth coat over the actual subfloor. Our house has 2x8 joists spaced 16" apart, on top of which is a continual subfloor composed of 2x6 lumber laid vertically against each other. There's maybe a 1/8" gaps between the vertical 2x6's where you can sometimes get a glimpse of the crawl space underneath but for the most part you'd be lucky to be able to slide a sheet of paper through.

My understanding was that the floor was built to be stronger than what is required these days... But as you can tell I really don't know much about this stuff at all.

And thank you to the person who told me the to is called a trowel! I knew that word as a verb but didn't know it was also the noun referring to the tool used to act out the verb! I feel like such a doofus, LOL

Anyway thanks again for the responses. I'm going to talk it out with my husband since he'll probably understand more of this than I do!

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Old 07-28-2014, 02:19 PM   #11
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Just to clarify, so I think our subfloor is six inches thick supported by 2x8 joists spaced 16" apart. The 2x6 lumber is attached to the joists at a 45 degree angle.
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Old 07-28-2014, 05:28 PM   #12
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Help! Need to remove uneven self-leveling compound from backerboard


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Just to clarify, so I think our subfloor is six inches thick supported by 2x8 joists spaced 16" apart. The 2x6 lumber is attached to the joists at a 45 degree angle.
Well, your subfloor is certainly not 6" thick - not sure what you meant by that! But 2x8s are OK. On top of that is most likely 1x6, not 2x6. And a 1x6 is usually about 3/4" thick. So it would be nice to have 1/2" plywood on top of that. But at least this isn't the 1/4" plywood over 2x6 joists that we thought.
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Old 07-28-2014, 05:54 PM   #13
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Help! Need to remove uneven self-leveling compound from backerboard


I only skimmed through all of the responses--so I may well cover the same ground---

When you peal off the old stuff---nail--screw or even staple down the 1/2" BC plywood--then buy 1/4" wonder board or Durrock--I dislike hardibacker and do not use it--use your 1/4"x1/4" trowel and lay down a bed of thinset--

Set the cement board on top and nail it down with 1 1/2" roofing nails--about 6" apart.
A roofing gun is a time saver if you can borrow one--but hand nailing that room is very doable---

Got to run--a friend is moving and wants to give me some odds and ends---Mike---
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Old 07-28-2014, 07:09 PM   #14
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Help! Need to remove uneven self-leveling compound from backerboard


The best way to install a tile floor is the old way. It is called a wet set. ASTM D-226 Type 2 felt is installed, typically over 23/32 BC Plywood. Wire lath is then installed over the felt, then about 1.5 inches of Portland rich and sand is mixed and placed damp. Your tile is then set on the mortar bed and wet grouted. The water in the grout goes down into the portland mix. WHen this sets up, you have one hell of a floor. Yes the sub-floor MUST be sound. ALL plywood has been made with exterior glue since about 1968.
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Old 07-28-2014, 09:33 PM   #15
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Originally Posted by jagans View Post
The best way to install a tile floor is the old way.
How can you know that? And how do you know it is better than an uncoupled system? After all, the true "old way" dates back to Roman times, and is an uncoupled system. The monolithic approach you mention is actually relatively modern, and strikes me as quite American.

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