Tiling a concrete floor - prep question
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Postmaster
Joined: Aug 2004
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From: North of Boston MA
Tiling a concrete floor - prep question
For my contractor friends out there....I am taking on another home project. I am going to tile my lower level family room floor. It is a concrete slab in good condition. Only thing is that when I pulled up the old flooring (vinyl tiles), most of the glue stayed on the concrete. So, the concrete is now 90%± covered with black mastic. It is a thin layer, very even and isn't even a little tacky. I have tried a couple solvents and some mastic remover but nothing will break it up.
Can I leave it and just tile over it? Planning to put 12x12 and 6x6 in a pinwheel pattern.
Also, should I just tile directly to the concrete or should I put an underlayment like Ditra?
Thanks, guys. Looking forward to the expert advice.
Can I leave it and just tile over it? Planning to put 12x12 and 6x6 in a pinwheel pattern.
Also, should I just tile directly to the concrete or should I put an underlayment like Ditra?
Thanks, guys. Looking forward to the expert advice.
is a BAAAD MAN
Joined: Apr 2005
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From: Winston Salem NC
That's cutback, nasty stuff. It has asbestos in it so at least wear a facemask. I would try a scraper to try to scrape it up it usually will come off that way. As long as you get the high spots off and use a really good thinset you shouldn't have any problems.
Hotshot
Joined: Oct 2003
Posts: 13,011
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From: Here in No. Calif
Your best bet Ray is to get some Sika Primer MB
I come across that (cutback) all the time and some people will say to skim coat with feather finish but I don`t trust that. Primer/sealer costs about $100 and what you do is scrape any excess cutback then roll this stuff on. It`s a simple two part mixture that after you roll it you have 2-3 days to cover it or you have to scuff it up. I get about 400' per bucket
I come across that (cutback) all the time and some people will say to skim coat with feather finish but I don`t trust that. Primer/sealer costs about $100 and what you do is scrape any excess cutback then roll this stuff on. It`s a simple two part mixture that after you roll it you have 2-3 days to cover it or you have to scuff it up. I get about 400' per bucket
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Postmaster
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From: North of Boston MA
Thanks everyone.
I actually had the stuff tested some time ago and the glue tested as clean, no asbestos.
I was hoping I could tile right over it so glad I asked first. The stuff is very hard and scraping it doesn't even scratch it. The solvents I have tried (including a pint of Goof Off which eats anything) did absolutely nothing. Guess I will go with the sealer. Nothing is ever easy in this house....
Thank you all again.
I actually had the stuff tested some time ago and the glue tested as clean, no asbestos.
I was hoping I could tile right over it so glad I asked first. The stuff is very hard and scraping it doesn't even scratch it. The solvents I have tried (including a pint of Goof Off which eats anything) did absolutely nothing. Guess I will go with the sealer. Nothing is ever easy in this house....
Thank you all again.
Senior User
Joined: Dec 2008
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The other option is to rent a concrete grinder from HD or Lowes. Get some aggressive diamond wheels and go over the entire floor. Lots of dust, but you'll have bare pure concrete after you're done.
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Postmaster
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From: North of Boston MA
It will probably turn out to be a waste of twenty bucks but I picked up a gallon of 747 Adhesive Remover at the depot the other day. It is supposed to remove cutback. Mixed reviews online but figured I would try.
I did notice something in the area where I tested the Goof Off....after I wiped it up and it dried, there is nothing left on the surface but the concrete still appears to be impregnated with the black stuff. In other words, I have nice smooth concrete, just black.
I'll probably try to get as much of this crap up using solvents as possible, then use the Sika product to seal it.
Anybody want to come lay this tile for me once it is ready?
I did notice something in the area where I tested the Goof Off....after I wiped it up and it dried, there is nothing left on the surface but the concrete still appears to be impregnated with the black stuff. In other words, I have nice smooth concrete, just black.
I'll probably try to get as much of this crap up using solvents as possible, then use the Sika product to seal it.
Anybody want to come lay this tile for me once it is ready?
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Hotshot
Joined: Oct 2003
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From: Here in No. Calif
I'll probably try to get as much of this crap up using solvents as possible, then use the Sika product to seal it.
Ray, your best bet will be to seal it and don`t bother solvents, besides the mess its like throwing money out the window. Sealer and a cheap paint roller and you are good to go.
Ray, your best bet will be to seal it and don`t bother solvents, besides the mess its like throwing money out the window. Sealer and a cheap paint roller and you are good to go.
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Postmaster
Joined: Aug 2004
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From: North of Boston MA
I do almost nothing outside between November and April. I have to work outside for my regular job...at home, winter is for indoor projects.
Ray, your best bet will be to seal it and don`t bother solvents, besides the
mess its like throwing money out the window. Sealer and a cheap paint roller and
you are good to go.
mess its like throwing money out the window. Sealer and a cheap paint roller and
you are good to go.
I was going to try some solvent from the place up the street but they just raised the price to $3.339.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
Thinning the mastic is just driving the asphaltum into the concrete.
Good that you have time, because it is best that you make sure it has all evaporated before trying to seal with epoxy.
How many square feet is it Ray?
Good that you have time, because it is best that you make sure it has all evaporated before trying to seal with epoxy.
How many square feet is it Ray?
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Postmaster
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From: North of Boston MA
It is about 17.5'x12'.
I read up on the Sika MB and was wondering if it is the right product for this. Sounds like it is for wood floors and for use with Sika adhesives.
I read up on the Sika MB and was wondering if it is the right product for this. Sounds like it is for wood floors and for use with Sika adhesives.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 39
From: EXTREME southwest CT
Ray, I went to the Laticrete website and surprisingly they don't have a recommendation for using sealer over cutback.
"
Can I install tile over existing vinyl or ceramic tile, or cut-back adhesive?
Yes. However, make sure of the following for each specific type of existing condition:
...............
Non-water soluble cut back adhesive (Interior Only) - Verify that the cut-back adhesive is not water-soluble by placing soapy water on the adhesive, allowing the solution to dwell for 10 - 15 minutes and then agitating with a stiff bristle brush. If the cut back adhesive starts to dissolve or soften, then it must all be removed. The flooring structure below the cutback adhesive must be the proper thickness. (e.g. If the cutback adhesive is installed over plywood - see LATICRETE TDS 152 "Bonding Ceramic Tile, Stone or Brick Over Wood Floors" for more information on the proper subfloor and underlayment thickness). Use 254 Platinum, or, 317 mixed with 333 Super Flexible Additive to install the tile."
So, I have to accept that you can probably go right over the mastic with a fortified thinset in combination with a latex flex additive.
"
Can I install tile over existing vinyl or ceramic tile, or cut-back adhesive?
Yes. However, make sure of the following for each specific type of existing condition:
...............
Non-water soluble cut back adhesive (Interior Only) - Verify that the cut-back adhesive is not water-soluble by placing soapy water on the adhesive, allowing the solution to dwell for 10 - 15 minutes and then agitating with a stiff bristle brush. If the cut back adhesive starts to dissolve or soften, then it must all be removed. The flooring structure below the cutback adhesive must be the proper thickness. (e.g. If the cutback adhesive is installed over plywood - see LATICRETE TDS 152 "Bonding Ceramic Tile, Stone or Brick Over Wood Floors" for more information on the proper subfloor and underlayment thickness). Use 254 Platinum, or, 317 mixed with 333 Super Flexible Additive to install the tile."
So, I have to accept that you can probably go right over the mastic with a fortified thinset in combination with a latex flex additive.
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Postmaster
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From: North of Boston MA
Pretty sure the cutback I have isn't water soluble. The first product I tried was for water based adhesives and it did nothing. I will try the soapy water though just to be sure.
Thanks again, Jim.