DIYbanter - View Single Post - continuing saga of my floor and a couple questions

wrote:

Ok now the questions

1) This floor is by no means down to clean concrete. There are remnants of
some sort of building paper they decided to put down in some places (and
oddly enough not in others, this is only a 12x12 room...) and there is old
adhesive etc.

Pretty sure I don't want to tile directly over this stuff. I have to level
the floor a bit anyway. What's the best way to prep this floor? Skim coat
it with leveling compound? Nail or glue hardibacker to it? I'd like to
keep the added height to a minimum. Do I have to sand all this crap off?
(god, please no)

Hardibacker is not put down over slabs. Have you tried using a razor
scraper on the paper and adhesive? As for the adhesive if it's stuck
good and next to impossible to scrape you can use modified thinset over
it. Read the bag and it will advise if it can be used over cutback and
other adhesives. But the adhesive can not be loose and chipping. Razor
scraper ad elbow grease. Buy a pack of blades with the tool.

As for level, being flat and even is more important so lay a
straightedge on the floor to check for flatness. In many cases you can
make some adjustments for minor low and high spots as you tile by
backbuttering etc, if the elevations are not to pronounced. Extreme
high points on the slab should be ground off. fwiw, floor levelers are
generally a pia for the beginner and if their use can be avoided, do so.

2) Before I was told I didn't have to use the fiberglass membrane for
keeping slab cracks from telescoping to the floor. This was due to the
vinyl tile being in place. Well it's gone now so I assume I have to use
this membrane product. Should I install that underneath or on top of
whatever flooring prep (leveler or hardibacker or whatever) I use.

Elastomeric membranes work and worth every penny. Especially helpful for
new slabs that are in the 'process' of curing. I'm partial to the ECB
product, but it must go over a clean floor. It would go down after you
use a self-leveler, if you do.