Removing tar adhesive from slab


  #1  
Old 01-10-03, 08:57 PM
tskoglund
Visiting Guest
Posts: n/a
Removing tar adhesive from slab

I'm planning on putting down ceramic tile on a slab that was previously covered with vinyl tile (probably about 50 years old). It appears that a black adhesive/mastic was used to set the old tile. I wanted to do the job right and planned on removing the black mastic adhesive, so I attacked about 20 sq. ft. of it with adhesive remover and a sharp edged heavy duty scraper. This effort proved to be extremely unsuccessful as the mastic became tacky and tar-like but virtually impossible to scrape up. I tried quadruple coating a small area and then using mineral spirits to clean it up with moderate success, but this approach is entirely impractical since I'd need ten years and a truck load of remover and mineral spirits to do the 500 sq. ft. of area I'm hoping to tile.

Perhaps this stuff is best removed mechanically rather than chemically, but I have no idea if there's any kind of machine (motorized sander/wire brush) for this approach that I can rent or buy.

Any suggestions?

I could leave the mastic adhesive and tile over over it, but I'm very uncomfortable about the prospects of tile prematurely coming loose and losing my $2000 investment in the project. The old tile came up rather easily and it's not hard to imagine the ceramic doing the same after a short while.

Thanks for the help.
 
  #2  
Old 01-11-03, 02:43 PM
brickeyee
Visiting Guest
Posts: n/a
Older mastics may contain asbestos.
 
  #3  
Old 01-11-03, 04:08 PM
Bud Cline's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: Central Nebraska
Posts: 1,296
Received 0 Votes on 0 Posts
You are right to be concerned but this can be done.

Use a 3-4 inch razor blade scraper. The one with the long handle (18"maybe) and go after the adhesive scraping up as much as possible. The chemicals don't work and could cause even deeper penetration of the black adhesive. The adhesive is known as "cutback" by the way.

Once you have removed as much cutback as is humanly possible then you can use a modified thinset rated for use over cutback adhesive to install your tile. Not to worry.
 
  #4  
Old 01-11-03, 05:45 PM
tskoglund
Visiting Guest
Posts: n/a
What precautions should I use if it happens to have asbestos?

Thanks for the hint on the modified thinset for application over cutback.
 
  #5  
Old 01-12-03, 08:22 AM
Bud Cline's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: Central Nebraska
Posts: 1,296
Received 0 Votes on 0 Posts
The asbestos thing is greatly overblown when it comes to flooring issues I think. Asbestos is only a threat when it is airborn and that ain't gonna be the case here.
 
  #6  
Old 01-12-03, 09:24 AM
hy
Visiting Guest
Posts: n/a
removal of black asbestos basedd mastic

There are chemical products made specifically for doing this job. There is Sentinel Products (Minneapolis) and Dumond Chemicals (New York) that make these products and they can be available to you at local outlets. A gallon will usually do about 100 square ft. and they are not that expensive. Time frame for removal is usuallu about 45/60 minutes and they are water washup
 
  #7  
Old 01-12-03, 11:42 AM
T
Member
Join Date: Aug 2000
Location: USA
Posts: 15,817
Received 1 Vote on 1 Post
Adhesive Removal

Some forum members report that a heat gun expedites adhesive removal with the scraper. As Bud recommended, don't forget to use the thinset for use over cutback adhesive. The Resilient Floor Covering Institute recommends wet scraping of cut back adhesive. If there is a chance of disturbing asbestos fibers, do not sand because, as Bud stated, it's only a threat if fibers are airborne.
 
  #8  
Old 02-11-03, 06:41 PM
tskoglund
Visiting Guest
Posts: n/a
Follow up

Here's my followup story: I ended up getting some Sentinel stripper since the concrete slab was rough and dulled my scraper very quickly. The stripper certainly did the job, but took a couple applications and some hard scrubbing with a wire brush, followed by detergent and TSP scrubbing to clean up the residue (Sentinel makes a clean-up product which I didn't buy) and a couple of rinses. I found that a 12" floor squeegee worked really well for gathering up the liquid tar that the stripper makes as well as the detergent and rinse water. You can spend your life savings using paper towels to absorb the liquid tar or you can buy a 40 lb bag of absorbent at an auto parts store for $5/bag. A shop vac works well for taking up the detergent and rinse water (saves time over a mop), but I wouldn't use it for the liquid tar.

The slab looked very clean after this process, but it took several days for the scent of the stripper to subside. The tile installer did not need to use a modified thinset.

The Dumond chemical stripper was about 50% more per gallon, but seemed to be a different type of product. I'd give either of them a shot. Sentinel's product certainly worked, but you've got to be willing to put in the time and to deal with the black tar mess. I used painter's masking plastic to cover the bottom 2 feet of the walls and caulked under the baseboards. If the stripper gets under the baseboard and walls, the odor of the stripper will persist a lot longer.
 
  #9  
Old 02-11-03, 07:07 PM
Bud Cline's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: Central Nebraska
Posts: 1,296
Received 0 Votes on 0 Posts
Thanks for the detailed report on using chemical stripper, sounds like it did a good job and also sounds like a lot of work.

One thing bothers me though....

"the tile installer did not have to use modified thinset"

OH-oh!!!
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: