Vinyl flooring and protection solution specialist Polyflor South Africa marketing director Tandy Coleman recommends two modern technology methods of removing bitumen from floors during floor removal.
“Bitumen can be very difficult to remove. Over the years many methods have been tried, some with success and some without,” she says, explaining that it was previously used as an adhesive and moisture barrier during floor installation.
She points out that a scabbling machine should be used to remove the top layer of the screed surface which contains the bitumen, provided the screed topping is hard enough.
Scabbling machines have a variety of uses but are predominantly used to remove stains or marks in concrete. It is ideal for use when removing material that is in excess of 1 mm thick.
The second method involves using an HTC grinding machine which can grind off the bitumen.
“These machines are available in different sizes for purchase or for hire and leave a very clean, smooth surface to begin floor preparation,” she adds.
Meanwhile, she points outs that modern self-levelling, smoothing compounds and acrylic adhesives are incapable of binding to bitumen.
“It is therefore essential to remove the bitumen before you can begin floor preparation for your new floor covering. If you do floor preparation over the top of bitumen, you face the risk of delamination and a failed installation,” Coleman warns.
“Chipping it off with a paint scraper is extremely difficult. Some success can be achieved grinding with a carborundum machine and using silica sand as a grinding medium,” she says.
In the past, various semiflexible tiles, sheeting and wood floors were installed using bitumen.
“Bitumen is inherently a waterproofing agent, which may have impeded the upward ingress of moisture. Bitumen is less affected by moisture than any other adhesive product and can therefore give a misleading impression that the original flooring was dry, which can give a misleading moisture reading when doing a surface moisture test,” she explains.
Owing to this, she notes that a below-surface moisture test is imperative and done by drilling at least 40 mm to 50 mm into the screed base.
“This is done to get an accurate reading of what is below the surface. A meter with probes or electronic sensors must be used to judge the moisture situation below the surface,” Coleman says.
Failure to do a proper moisture test may cause adhesion problems after the new flooring is installed, and will be difficult and expensive to rectify.
According to Coleman, a moisture barrier should be applied if necessary.
“Once the moisture barrier has been applied, the surface should then have a blinding layer of screed or cement material applied over the dampproof membrane. Because bitumen seeps into the screed, there will always be an invisible trace of bitumen left behind, therefore, this blinding coat is advisable to block out the effect of any bitumen leaching into the newly applied adhesive,” she notes.
It is advisable to remove dust and surface contamination before applying a primer coat of bonding liquid from the same product range that you will use for the blinding or blocking coat.
Coleman says a suitable and approved screed or cement product should be used, as not all screed compounds will be suitable for this type of application.
She advises consulting product manufacturers about their recommended mixing instructions.
Screed preparation should continue after the blinding coat has been applied.
“When planning a building renovation, be sure to check if bitumen was used to ensure adherence of previous floor coverings. That way you can allow for sufficient time, budget and preparation for removal without any nasty surprises or delays in your project,” Coleman concludes.