Debunking the bitumen myth

by Madelein
Debunking the bitumen myth

A little is ok, right?

Strangely, one of the most pertinent challenges has been correcting the misinformation about bitumen. Some believe it does not need to be removed before installation, but this is not true. We are not quite sure where this myth originated, however, as a team of seasoned flooring specialists, Polyflor can assure customers that it is never a good idea to leave any amount of bitumen behind when refurbishing a floor.

It must be completely removed!

Bitumen can cause issues with the new water-based adhesives available in the marketplace. As vinyl creates an impermeable barrier once installed, any moisture trapped within the screed will look for an escape route and, in the process, create a reaction with any adhesives, self-levelling compounds and moisture barriers in the vicinity.

Bitumen acts as a moisture barrier as well as an adhesive. Moisture can therefore be an issue so a moisture test must always be conducted when removing bitumen. An old installation doesn’t necessarily mean a dry screed and we often encounter very wet screeds when old floors are lifted.

To help you understand some of the key issues, Polyflor has compiled a list of frequently asked questions.

Q: What is bitumen?
A: Asphalt, also known as bitumen, is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or be a refined product and is classed as pitch.

Q: What is bitumen used for?
A: In the past, many types of flooring including semi-flexible tiles, sheeting and wood floors were installed using bitumen-based adhesive. It is also a reasonable waterproofing agent and, as a result, quite successful as both an adhesive and a moisture barrier. However, modern products are more effective and less harmful to the environment.

Q: Why is bitumen not used anymore?
A: Bitumen is still used in flooring but over the years there have been many advancements in the field of flooring, including with adhesives that are used in the process. Bitumen is a challenge to remove and makes future renovations difficult due to the effort that must be put in to ensure that your floor is clean of this substance prior to new applications.

Q: I have removed my existing floor and found bitumen, what do I do now?
A: When removing an existing floor, bitumen is easily identified as a black substance that is firmly adhered to the screed, remaining behind after the floor covering is removed. Due to the nature of bitumen, it seeps into the screed and is therefore very difficult to remove.

Q: How do I remove bitumen?
A: Bitumen can be a challenge to remove and over the years many methods have been tried. Sanding it off, using a scraper or grinding can introduce several challenges; however, with modern technology, two methods are recommended:

• Method 1 for removing bitumen from floors
The first method requires the screed topping to be hard so that a scabbling machine can be used to remove the top layer of the screed surface, which contains the bitumen. However, if the screed topping is soft, this method could destroy the entire topping.

• Method 2 for removing bitumen from floors
The second method involves using an HTC grinding machine. These machines are available in different sizes for purchase or for hire and leave a very clean, smooth surface. If neither of these is available, the manufacturer of the screed preparation products should be contacted for further advice and assistance.

Q: Can vinyl sheets be laid over bitumen?
A: Unfortunately, modern self-levelling and smoothing compounds as well as acrylic adhesives are unable to bind to bitumen. It is therefore essential to remove the bitumen before commencing with floor preparation for installation of a new floor covering.

For expert advice, contact Polyflor SA:
Tel: +27 (11) 609 3500 (speak to Blythe or Wendy)
Email: marketing@polyflor.co.za
Website: www.polyflor.co.za

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