Focus on floors: your questions answered

We've picked some of the most frequently-asked questions from the hundreds answered by F. Ball’s technical team in the past few weeks.

Q. I’ve smoothed a calcium sulphate screed with F. Ball’s Stopgap 1100 calcium sulphate based levelling compound. Can I now skim with Stopgap 300 HD?

A. Although there isn’t an advantage to doing so (Stopgap 1100 will provide a perfectly smooth base for the receipt of floorcoverings), you can, providing it’s dried sufficiently. You’ll first need to apply a primer to help the Stopgap 300 adhere to the previously applied levelling compound. F. Ball recommends the use of its Stopgap P121 primer, which is specially designed for use over calcium sulphate screeds. It should be applied in two coats; the first coat should be diluted with one part primer to one part water. The second one should be applied neat. Once dry, you can apply Stopgap 300 HD to finish if preferred.

Q. Can I apply a levelling compound over a waterproof surface membrane that was installed six months ago?

A. In order to be an effective barrier preventing excess subfloor moisture rising up to the level of floorcoverings and potentially causing complete floor failure, the waterproof surface membrane will need to form an uncompromised layer over the subfloor. Therefore, it’s advisable to inspect the waterproof surface membrane for damage ahead of the application of a levelling compound. And don’t forget to prime the waterproof surface membrane to promote the adhesion of the levelling compound to the waterproof surface membrane. F. Ball’s Stopgap P141 primer for use over non-absorbent surfaces is ideal for this.

Q. Can you recommend a water-based adhesive for installing carpet?

A. F. Ball’s Styccobond F3 is a water-based rubber/resin flooring adhesive, which is suitable for securing most types of carpet, hessian, felt, secondary latex and rubber foam-backed carpets and cork tiles up to 3.2mm thick. It offers excellent wet grab, which quickly builds to a high bond strength. It is also suitable for use over normal underfloor heating installations. You can check the compatibility of particular carpet floorcoverings with F3 by consulting F. Ball’s Recommended Adhesives Guide (RAG), which lists over 6,000 adhesive recommendations for floorcoverings from over 200 manufacturers. The 2019 version of the guide is available as an app to download for your mobile device and an A5 printed booklet. Access an interactive version of the guide online here.

Q. I’m applying Stopgap F77 waterproof surface membrane, followed by P141 Primer, followed by Stopgap 300 HD over a concrete subfloor with underfloor heating. How long should I leave the underfloor heating off beforehand?

A. You should turn off the underfloor heating 48 hours before work begins, and have it turned off throughout the installation and for 48 hours afterwards. Then you should bring the temperature up gradually over seven days. Refer to the underfloor heating manufacturer’s guidelines for instructions on how to do this.

Q. I want to install plywood over a metal raised access floor. What’s the best way to do this?

A. This can be done mechanically, using screws at frequent intervals. For a non-mechanical alternative, there’s F. Ball’s Stycco Flex. The highly versatile tube adhesive can be used to bond almost any two absorbent/non-absorbent surfaces together, including two impervious surfaces, in as little as 60 minutes, so it’s ideal for a quick, easy and effective solution.

Q. I’ve applied Stopgap F77 in a building that is very cold and it is not curing.

A. Low temperatures can cause waterproof surface membranes to cure more slowly. If the appearance is consistent across the surface, and there is evidence it has begun to cure evenly, this is likely to be the case. Allow more time for the waterproof surface membrane to cure. Meanwhile, try to warm the environment inside the building. If this doesn’t work, it’s possible that the two components of the product haven’t been mixed properly. In this case, you’ll have to scrape the surface and reapply Stopgap F77 that has been properly mixed. 

Our technical team are on standby to answer questions about your projects and F. Ball products from 7.30am – 5.00pm, Monday to Friday.

Please note: site conditions vary. Don’t rely on these specific responses for your own project. If you are unsure about any technical issue relating to specific flooring installations, contact the F. Ball Technical Service team on 01538 361633 or consult the product data sheets available from F. Ball’s website.