AccuRoof Technical Director Daniel Bosworth discusses the key performance and applicational benefits of Remmers MB PUReactive liquid-applied waterproofing membrane for cold concrete balconies with Architecture Today’s Technical Editor John Ramshaw.

Made by Remmers – one of AccuRoof’s preferred partners – MB PUReactive is a liquid-applied waterproofing membrane that is particularly suited to cold concrete balconies (photo: Remmers).

AccuRoof has recently added the MB PUReactive liquid-applied membrane to its extensive waterproofing portfolio. Made by Remmers – one of Europe’s leading manufacturers of construction coatings and repair systems – the company has become one of AccuRoof’s preferred partners, supporting its broad-based, product-agnostic approach to roofing design and specification. AccuRoof Technical Director Daniel Bosworth, in conversation with Architecture Today’s Technical Editor John Ramshaw, discusses why MB PUReactive is particularly suited to cold concrete balconies, and how AccuRoof supports its use through expert technical guidance and national distribution.

What is PU hybrid waterproofing?
PU hybrid waterproofing is a type of water-based, elastomeric coating that combines polyurethane and acrylic resins to create a flexible, water-resistant membrane. MB PUReactive is a hybrid liquid-applied membrane made from a simple one-to-one mix of powder and liquid. Unlike PMMA (polymethyl methacrylate) systems, which generally require precise catalyst dosages depending on volume and temperature, MB PUReactive eliminates that complexity. The standard kit contains a single large tub with a bag of powder and a bag of liquid; smaller TX and + (plus) variants of MB PUReactive include three sets of pre-measured components for easier partial use. Furthermore, the product offers a generous working time (or pot life) of up to 90 minutes, which is substantially longer than PMMAs, which often cure within 30 to 45 minutes. This gives installers greater flexibility and reduces the risk of wasted product on site.

MB PUReactive is made from a simple one-to-one mix of powder and liquid (photo: Remmers).

Why does AccuRoof favour Remmers’ MB PUReactive for cold concrete balconies?
The key advantage is fire performance. When applied to concrete, MB PUReactive achieves an EN 13501-1 fire classification of B-s1, d0. This exceeds the minimum requirement (B-s3, d0) for membranes applied to the face of an external wall under Approved Document B. Most alternative systems either carry no relevant classification or revert to Class E when tested in similar conditions.

Does MB PUReactive have any other key performance benefits?
Yes. In addition to its fire classification and ease of mixing, MB PUReactive is compatible with most mineral-based substrates, including concrete, without the need for primers – provided the surface is clean, sound and level. Cracks or defects can be filled using compatible Remmers fillers, and no separate primer is required for porous mineral-based substrates. It also offers good adhesion to A1/A2 fire-rated building boards and concrete, and avoids the need for harsh chemical solvents. Application is low-odour, with only a degreaser needed for metal substrates and a dedicated primer for PVC single-ply membranes. MB PUReactive is also available in a spray-applied variant (MB PUReactive +)making it suitable for fast-track ‘regeneration’ works. This version includes embedded reinforcement within the liquid itself, allowing for coverage rates of up to 150-square-metres per day.

BBA-certified (certificate No. 24/7253), MB PUReactive has a stated service life of 25 years (photos: AccuRoof).

You touched on the different products within the range. Which ones do you recommend and why?
Each version is designed for a specific application. MB PUReactive is a fleece-reinforced, liquid-applied system used for field areas. Applied as a ‘liquid-fabric-liquid’ build-up, it is compatible with brush or roller application. MB PUReactive TX is a thicker grade version used for upstands and detailing. It is applied before the main field areas and offers robust edge protection. It is also installed as a ‘liquid-fabric-liquid’ system. MB PUReactive + is a spray-optimised system used for high-speed applications and regeneration works. It eliminates the need for a separate fleece due to the product containing fibre reinforcement, making it ideal for overlay applications.

Applied as a ‘liquid-fabric-liquid’ build-up, MB PUReactive is compatible with brush or roller application (photo: Remmers).

Are there any disadvantages to using MB PUReactive?
The main limitation is colour choice – it is only available in grey. Additionally, while it is BBA-certified and approved for use in green roof systems, MB PUReactive does not yet form part of an AccuRoof approved warm roof system.

Does MB PUReactive provide flexibility in terms of application and fixing methods?
Yes. It can be applied using brush, roller, or spray equipment, depending on the chosen variant. As such, the system offers flexibility for both new-build and retrofit installations, including complex geometries and hard-to-access balconies.

MB PUReactive + is a spray-optimised system used for high-speed applications and regeneration works (photo: Remmers).

What backing does MB PUReactive have in terms of certification and warranties?
MB PUReactive is BBA-certified (certificate No. 24/7253), with a stated service life of 25 years. When specified and supplied through AccuRoof, it is supported by a project-specific AccuRoof warranty, backed by SIG Trading Ltd, a FTSE 350 company.

What advice would you give architects looking to specify MB PUReactive for waterproofing cold concrete balconies?
Talk to us early in the design process. AccuRoof can provide NBS specifications, detailing advice, and approved contractor recommendations. We work with architects to ensure waterproofing is compliant with relevant British Standards, including maintaining 150mm upstands above finished floor level, and coordinate key interface details like door thresholds, balustrade fixings, and handrails. Getting the detailing right at the outset ensures lasting performance and regulatory compliance.

Contact details
To discuss a project or request technical support, please call 01509 505 714, email, or visit the AccuRoof website.