Victoria Ramwell, commercial manager at cold-applied liquid waterproofing specialist, Kemper System, explains the benefits of using Poly Methyl methacrylate (PMMA) as a liquid applied waterproofing membrane, and offers specification advice.
The popularity for PMMA liquid waterproofing solutions – (Polymethyl Methacrylate) – has grown in recent years, but the technology isn’t a new concept. PMMA was first developed more than 90 years ago and many liquid waterproofing manufacturers, including Kemper System, have offered a PMMA solution as part of their portfolio for many years.
The success of PMMA relies on its rapid curing qualities as it can dry in 30 – 40 minutes and in some cases even quicker if required, by using additional catalyst. This has proved increasingly popular for time-poor contractors working on predominately occupied areas such as car parks, public walkways or residential balconies, when time on site is restricted.
Advantages of PMMA
As well as quick curing, PMMA is durable, flexible and hard wearing. The cold-applied liquid resin cures rapidly even at temperatures around 0°C or lower, and is installed wet-on-wet. This means the polyester reinforcing fleece is first saturated with liquid resin, bonding the membrane to the substrate, with the surface layer then applied onto the bonding coat whilst still wet – therefore forming a single, seamless membrane of uniform thickness.
PMMA is tough and robust, and can provide a sound waterproofing solution for decades, providing care is taking during preparation and installation stages.
Preparation is key when it comes to PMMA, especially during the colder winter months. Many contractors don’t realise just how fast curing this solution is, and everything will need to be in place and ready before installation.
One example is being mindful of the weather and potential changes of the forecast throughout the day. Fluctuating temperatures can create moisture on the substrate which in turn, will have an impact on the cure. Using a catalyst controls the cure better with PMMA systems, but contractors can sometimes be caught out by changing temperatures and resulting dew points.
Most manufacturer’s product datasheets or certifications will give recommendations regarding the minimum temperature for application so contractors must read these carefully before use. This is particularly important as moisture present on the substrate could significantly affect adhesion and compromise the quality of the waterproofing.
PMMA-based systems tend to have a minimum of two components, the first being the resin and the second being a catalyst or activator. Contractors will mix the components together on site, starting the chemical reaction that initiates the rapid curing process. Contractors should be aware that this process generates a degree of heat.
As with any liquid waterproofing product, it is vital that contractors ensure the substrate is clean, dry and stable prior to application. Contaminants such as vegetation or moss, dust and dirt must be removed and ensure the surface is dry. Concrete surfaces should be relatively smooth, void free and peaks and troughs limited to 2mm. PMMA’s can also be applied over the majority of existing roof waterproofing systems such as single ply and asphalt, subject to following the manufacture’s preparation guidelines.
Support on site is paramount to any liquid waterproofing application, and when it comes to the quick curing qualities of PMMA, time is of the essence. Manufacturers should offer on-site support during installation to ensure any potential errors can be rectified prior to application – a service provided by the experienced and knowledgeable technical team at Kemper System.
Manufacturer training for PMMA systems is a must, and products should only be specified and applied by specialist contractors that have undertaken this training. Not all PMMA systems behave the same way, and manufacturers will have different methods of priming and installation – which is why training is vital.
There are some PMMA solutions which are very new to the market. Because of its popularity, some solutions are being sold without the correct certification or testing, or company experience to back-up the specifier or contractor should anything go wrong.
Be mindful to choose a PMMA solution from a reputable manufacturer with ample experience and who offer contractor training to ensure operatives are fully skilled and knowledgeable about the product and how it works.
Reputable manufacturers, such as Kemper System, should be members of key industry associations, such as the Liquid Roofing and Waterproofing Association (LRWA), and have appropriate third-party accreditation such as BBA Certification and/or BDA Agrement (Kiwa).