Focus on floors: your questions answered

F. Ball’s technical team answers hundreds of questions about F. Ball products and specific projects every month. We pick some of the most commonly-asked questions in the past few weeks.

Q. An electric underfloor heating system needs to be installed over a new screed and a waterproof surface membrane is required beforehand. What should I use?

A. F. Ball’s Stopgap F77 is suitable for use over new sand/cement screeds where relative humidity levels in the subfloor are between 75% and 98% RH. Just make sure that the screed is suitably sound, smooth and free of contaminants beforehand. Prime the membrane with Stopgap P131 or P141 and then use Stopgap 300 HD to encapsulate the wire underfloor heating system.

Q. I’m installing wood floorcoverings over a newly installed sand cement screed, how long do I need to allow for the screed to dry?

A. The screed must be at least seven days old before the application of any floor preparation products. Then a moisture test should be conducted. Where the relative humidity (RH) levels in the subfloor are above 65% and wood floorcoverings will be installed, a waterproof surface membrane will be required.

Q. How should I prepare a calcium sulphate screed with underfloor heating ahead of the application of a levelling compound.

A. The screed should be given sufficient time to dry before removing any laitance and dust and priming with Stopgap P121 – F. Ball’s primer for calcium sulphate screeds. Finally, the underfloor heating system should be turned off at least 48 hours before, during and after the application of a calcium sulphate-based levelling compound, such as F. Ball’s Stopgap 1100 Gypsum.

Q. I’m installing LVTs in a glass-sided building. What’s the best adhesive to use?

A. Styccobond F49 is recommended for installing vinyls in areas exposed to extreme temperature fluctuations, such as areas with floor to ceiling windows. Its pressure sensitive characteristics also make it ideal for installing LVTs as the strong initial tack holds floorcoverings in place during installation. Don’t forget to check compatibility with floorcoverings by consulting the floorcovering manufacturer’s guidelines and F. Ball’s recommended adhesives guide (RAG).

Q. After removing old carpet tiles ahead of installing new floorcoverings as part of a refurbishment, tackifier residues are present. What do I need to do?

A. Traditionally, contractors would have to remove old adhesive residues completely. This can be done using mechanical means or by sand or grit shotblasting. Alternatively, there’s F. Ball’s Stopgap 1200 Pro levelling compound – developed especially for use over old adhesive residues, with no need to prime.

Q. I’ve used a digital hygrometer to check the moisture levels in a concrete subfloor that’s six months old. The reading fluctuates between 92–98% relative humidity.

A. The reading on a digital hygrometer can vary depending on ambient temperature and humidity. In this case, the floor’s still damp enough to cause problems. To ensure against floor failure, use Stopgap F77 waterproof surface membrane to impede the passage of residual construction moisture up to 98%RH.

Q. The subfloor is contaminated with oil and antifreeze. What can I do to prepare it ahead of the installation of floorcoverings?

A. F. Ball’s Stopgap Isolator Membrane is ideal for subfloors that are contaminated and cannot be prepared by traditional methods. Otherwise, you’d need to replace the screed.

Q. What temperature tolerant adhesive should I use over underfloor heating systems for installing carpet.

A. It’s not necessary to use a temperature tolerant adhesive over normal underfloor heating systems. For your installation, you can use F. Ball’s Styccobond F3. You just need to turn the heating off 48 hours before the installation, and 48 hours afterwards.

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

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.