This month the Inspector warms to the task of how best install cold applied liquids.
Cold applied liquids are fast becoming the solution of choice – particularly in the domestic flat roofing market – as they provide quick and effective answers to both repair and refurbishment scenarios. Ideal for extending the life of tired and ageing roofs, they also provide solutions for new projects as they now achieve guarantees comparable to bitumen and single-ply membranes. This, however, as always, is dependent on the correct preparation and application of the waterproofing system by the contractor.
Whilst they offer a speedy installation (when compared to other systems), it by no means implies they should be applied quickly. Far too often we see the threat of inclement weather force the contractor into rushing the installation where the manufacturer’s recommended coverage rates are not observed, primers are ill applied and substrates are ill-prepared. Our very first column on substrate reparation (Total Contractor – April) should be heeded here; now is a good time to re-emphasise its importance and that by failing to prepare you are effectively preparing to fail.
Is the forecast good?
Of course the success of liquid applied systems is subject to friendly weather, but it is equally dependent on the care and attention of the installing contractor. It is essential that you check the weather before starting a project of this nature as rainfall will most certainly compromise the system’s integrity and will also effect its curing potential, which can mean the whole system needs reapplying in its entirety – a costly mistake to make for any contractor who makes naive assumptions about the UK’s weather.
There are usually various curing stages so it is also essential the manufacturer’s guidance and recommendations are followed. Some products may be ‘rain proof’ after a few hours, they may be considered suitable to receive foot traffic several hours after that, but their fully cured state may not actually be achieved until 24 hours after initial application. Manufacturers may give advice on a product’s colour, tackiness or odour to identify these particular stages, so please check the relevant literature for confirmation.
It is also essential that the liquid be measured out accurately prior to application, as coverage rates will often determine guarantee lengths. If insufficient liquid is applied, a guarantee may not be awarded for the project and the system itself may still be vulnerable to ingress, particularly if reinforcing fabrics are still visible beneath the liquid, which is something we still see quite regularly, as shown in image 1 above.
Another issue that we commonly find is the system being applied onto substrates that are still wet or damp. Whilst the waterproofing system itself is wet on application, it does not mean the substrate receiving the liquid can be wet too. Any retained moisture will provide a barrier between the surface and the waterproofing; this may result in pockets of unbonded system being present which could lead to blisters and system delamination, as illustrated in the picture above (image 2). This is not aesthetically pleasing and damage to these pockets could result in a system breach.
This can also occur if the wrong primer is used on the wrong substrate. Most liquid systems have
substrate specific primers, so the primer for a timber substrate may be different to the primer for a PVC membrane. Installing the incorrect primer could lead to full system de-lamination and therefore full system failure!
When a liquid system is applied correctly, it will provide a long-lasting and durable finish with no
side or head laps which naturally improves its integrity. A seamless product has the ability to offer a seamless installation when applied correctly.
Five steps to success:
- Check the weather forecast before starting
- Ensure all substrates are dry
- Use the correct primer
- Ensure the correct coverage rates are measured and observed
- If in doubt, consult the manufacturer