Black glue or mastic on the terrazzo under old vinyl tile

Black adhesive under old vinyl tile has to be tested for asbestos before anyone grinds, sands or scrapes it. If the test is negative, it grinds off with the rest of the surface at the usual $2 to $3 per square foot for removal plus the $5 to $9 per square foot grind. If it is positive, the removal method changes, and so does the price, which is quoted after the test result.

Check this first

1. Stop where you are. If you have pulled up some vinyl and found black glue, do not scrape, sand, heat or sand-blast it.
2. Look at the color and texture. Black or very dark brown, tar-like, sometimes in ridges from a notched trowel, is the kind to test. Yellow, tan or clear adhesive is a different product, but a test still costs little next to guessing.
3. Look at the tiles too. If any of the old vinyl tile is still down, leave it whole. The EPA lists “vinyl floor tiles and the backing on vinyl sheet flooring and adhesives” among materials that may contain asbestos.
4. Note the year built. On the Hillsborough County Property Appraiser record, a house from the mid-1950s through 1970 is the age where terrazzo was standard, and any vinyl laid over that floor could be decades old.

What is behind it

What testing involves

A small sample of the adhesive, and any tile still down, is sent to an accredited lab. The result tells you whether it contains asbestos. That one result decides everything that follows:

• Negative: the mastic is just glue. It comes off in the metal-bond grinding passes along with the dull top skin of the terrazzo. We grind wet or with vacuum shrouds, as OSHA’s silica rule calls for on floor grinders, because terrazzo dust is its own hazard.
• Positive: the floor is handled as asbestos removal under the rules that apply to it. That is a different job with different methods, and we tell you that plainly before anything happens. We do not grind positive mastic.

Why it turns up in Hillsborough houses

Terrazzo floors in the county’s mid-century block houses were covered over the decades with whatever was fashionable. In our pull of 1,103 county property records, 44 of the 464 houses built between 1950 and 1972 list vinyl as their flooring, and on West Reynolds Street in Plant City it was 5 of 19. Some of those vinyl floors sit directly on terrazzo. The property-record guide explains how to read your own house’s record.

Do not make it worse

The worst outcomes start with good intentions:

• Sanding or a floor buffer with a sanding screen puts any fibers into the air. The EPA says not to sand or try to level asbestos flooring or its backing.
• Solvent strippers soften the mastic and wick it deeper into the cement matrix, where it can leave a dark shadow that outlasts the grind.
• A heat gun softens it and can release fumes.
• Scraping with a sharp blade gouges the terrazzo.

Leave it as it is, keep the area closed off and test it.

When to call

Once you have seen the black glue, or before you pull any vinyl at all. Send a photo of the glue with a coin beside it and the area involved. We will tell you what we see and how testing fits into the job. If the test comes back negative, the rest of the work is a normal carpet, tile and glue removal followed by restoration, priced from the pricing page.