Environmental Effects on Waterproofing

There are many environmental factors that come into play when waterproofing with most waterproofing membranes, whether they are single pack or two pack, water-based or solvent-based.

Some of the most common environmental factors that can adversely affect the drying and/or curing of waterproof membranes include:

Ambient temperature
Substrate temperature
Air flow
Humidity
Substrate moisture content

Let’s look at each of those factors and see what affect they have.

AMBIENT TEMPERATURE

Most waterproofing membranes, especially one-part water-based products have an ideal drying/curing temperature (They are usually tested at either 23°C or 25°C). Outside this range, you can expect a change in the time in which the waterproof membrane will dry and/or cure.

For example, a product such as Bluproof, which states that it will dry (ready for re-coat) in 2 to 4 hours at 23°C, will take longer to dry at lower temperatures, and will probably not dry at all below 10°C (specific recommended 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°C, most waterproofing membranes will dry too quickly (especially two-part products such as Gripset 2P), 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 below a very dry surface, and will often re-emulsify and/or bubble on contact with water.

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

SUBSTRATE TEMPERATURE

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°C, if the substrate temperature of the concrete slab that you’ll be applying the waterproofing 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 waterproofing membrane to properly cure prior to allowing any further work on it such as tiling. 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 or use a more suitable product.

AIR FLOW

Adequate air flow is very important to ensure that as the waterproofing 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 waterproofing membrane not drying in a timely manner. And whilst this will affect single pack membranes such as Gripset P39 much more than two pack membranes such as Mapelastic Smart, almost all waterproofing 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.

HUMIDITY

High humidity will generally only affect water-based products, as solvent-based products such as Multithane STD are in general moisture curing.

However, humidity can be a real issue for water-based membranes as water-based membranes such as Gripset 38FC 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 waterproofing membrane will dry and/or cure will be greatly affected, to the point where the membrane in some circumstances stop drying entirely. This is especially a problem in enclosed environments without ventilation, but in some cases can be an issue with outdoor environments which are completely enclosed by walls, especially on days where the temperatures are very low.

Most membrane drying times are tested at a relative humidity of 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.

SUBSTRATE MOISTURE CONTENT

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

In the case of single pack water-based membranes such as Azcothane, 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. It is highly recommended to test the moisture content of suspect areas with a moisture meter prior to applying a waterproofing membrane as moisture levels above 8% are generally classified as unsuitable and should either be left to dry or appropriately primed with either a suitable epoxy primer or a specialist primer such as Gripset Xpress H20 Plus.

In the case of solvent-based membranes such as Multithane HV, 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 Primeseal MC.

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 no way of guaranteeing a positive result.