Environmental Effects

Most waterproof membranes, especially one-part water-based products have an ideal drying/curing temperature. Outside this range, you can expect a drastic change in the time in which the waterproof membrane will dry and/or cure.

For example, a product such as Aquathane-XR, which states that it will dry (ready for re-coat) in one hour at 20 degrees Celsius, will take longer to dry at lower temperatures, and will probably not dry at all below ten degrees Celsius (specific variations in drying times will vary from product to product).

The converse is also true, that higher temperatures will cause the membrane to dry faster, however, once you go above about 30-35 degrees Celsius, most waterproof membranes will dry too quickly (especially two-part products such as Duram Crystoflex), causing a problem with surface crazing and/or cracking as the moisture is leached out of the surface of the membrane too quickly.

This is especially problematic where you have a combination of high temperatures and strong winds, which simply doesn’t give the still wet internal parts of the membrane a chance to release the moisture before the top layers are fully dry, causing a situation where the membrane appears to be dry, but is in fact still wet on the inside, and will often re-emulsify on contact with water.

In both cases where the temperature is quite low or quite high, you are better off applying multiple thin layers of waterproof membrane rather than trying to apply thick layers.

Whilst the ambient temperature plays a very important role, so does the substrate temperature. Consider that whilst the air temperature in a room may be 20 degrees Celsius, if the substrate temperature of the concrete slab that you’ll be applying the waterproof membrane on is only 5-10 degrees Celsius, then it will dramatically influence drying and curing times.

You should take appropriate measures to ensure that adequate time is given for the waterproof membrane to properly cure prior to allowing any further work on it such as tiling, or if you are expecting adverse weather conditions (when working outdoors), then the best course of action may be to delay the work until better conditions prevail.

Adequate air flow is very important to ensure that as the waterproof membrane releases whichever agent is responsible for keeping it liquid (water or solvent), the air near the membrane is circulated away from it, thus allowing the membrane an opportunity to “breathe”.

In the case of an enclosed room with limited ventilation, stale air is the most likely cause of a waterproof membrane not drying in a timely manner. And whilst this will affect single pack products such as Durabit Reo much worse than two pack products such as Gripset 2P, almost all waterproof membranes will be adversely affected by a lack of decent air flow.

You can almost always alleviate this issue by pointing a pedestal fan into the waterproofed area and keeping the window(s) and/or door(s) open. Increasing air flow will also assist if other factors such as temperature or humidity are less than ideal.

High humidity will generally only affect water-based products, as solvent-based products are in general moisture cured.

However, humidity can be a real issue for water-based membranes as water-based membranes such as Ultraflex RX are entirely reliant upon the release of moisture from within the membrane into the surrounding atmosphere in order to dry. If the surrounding atmosphere is already saturated with water (high humidity) then the rate at which the membrane will dry and/or cure will be greatly affected, to the point where the membrane in some circumstances may not dry at all. This is especially a problem in enclosed environments without ventilation, but in some cases can be an issue with outdoor environments that are completely surrounded by walls, especially on days where the temperatures are very low.

Most membrane drying times are tested at a relative humidity of about 50%, so humidity levels higher than that will invariably result in a slowing down of drying and curing times.

Again, it cannot be stressed highly enough that adequate airflow must be maintained to reduce humidity levels near the waterproof membrane.

In cases where the relative humidity of the actual environment is very high, just like with high or low temperatures, it is usually a good idea to apply multiple thin coats of membrane rather than two thick coats.

The moisture content of the substrate has two very different effects on water-based and solvent-based membranes respectively.

In the case of water-based membranes, the moisture content in the substrate will slow down the rate at which the membrane dries, and in extreme cases may entirely stop the membrane from drying if the substrate is saturated.

In the case of solvent-based membranes such as Multithane, it is in most cases very difficult to apply the membrane directly onto the substrate without the use of an adequate epoxy primer/vapor barrier such as Hydrostatic Epoxy.

In the case of water-logged screeds (such as on a balcony after rain), it is vital for the screed to be allowed to completely dry out prior to applying a waterproof membrane on it, as even the use of a vapor blocking epoxy is unlikely to have a positive outcome. If work must be carried out urgently, adding a cement component into the epoxy vapor barrier coatings (minimum of 2 coats) may work to prevent subsequent membrane failure, but there is now way of guaranteeing a positive result.