Solving the issue of leaks and EIFS with primers

A situation arising in which the Exterior Insulation Finishing System is actually leaking itself is very rare. Leaks or moisture intrusion are usually due to other issues like weak joints, improper installation below and near grade or the EIFS’ proximity to openings such as windows.

However, despite this rarity, there are several precautions that can be taken to ensure the coatings on the EIFS are impervious to leaks and moisture intrusion. Most EIFS manufacturers produce primers that can be applied over the base coat and prior to the application of the finish, as well as coatings that can be applied over the finish. Primers and coatings can help increase the water resistant properties of EIFS and in fact in Europe, the birthplace of EIFS, primers are mandatory.


Depending on the colours of both the base coat and the finish, the base coat may be darker or lighter than the colour of the finish and therefore darken or lighten the colour applied over it, changing the colour of the final, finished product. Incorporating a primer on top of the base coat, just like painting the interior walls of a house, can create a blank and colourless canvas for the finish to be applied onto. This interior wall-painting analogy also can transfer over to rectifying thickness and surface uniformity problems. Primers will smooth out any thickness differentials with regards to the base coat, so there is no risk of having thin areas which will become more susceptible to moisture intrusion later on down the road, as well as increase the “flatness” of the surface upon which the finish is applied, leading to better adhesion and less likelihood of spaces occurring where water can get in.

If errors in applying the EIFS result in poor water resistance performance, these issues can be tested for by using a RILEM tube, a testing method devised to see how much water is absorbed by walls.


Obviously the aforementioned use of primers is only suited to new constructions and fresh applications of EIFS. One cannot remove the finish, apply a primer and stick the finish back on without incurring problems later.

To achieve the same amount of water resistance without using a primer, a coating may be applied over the exterior of existing EIFS. Note that this method is only effective if it is truly indeed the lamina itself that is the source of the leaking, although rare. Applying a coating will not solve moisture intrusion attributed to poorly sealed joints or other problems.

Coatings with certain properties must be used in climates like Ontario and south eastern Canada, where freezing temperatures are a yearly occurrence. This freezing has adverse effects on any condensation that may be present by causing it to expand when frozen, and so considerations should be taken when utilizing coatings so that the components of the EIFS are not pushed off of each other and do not separate.

Coatings used on EIFS can generally be sourced directly from the manufacturer. Using coatings not specified for EIFS can result in some serious problems, especially if they contain solvents that would eat through the finish and dissolve the insulating foam. Elastomeric or water-based coatings are much more suited to EIFS purposes, and they should have a higher vapour permeability so that new condensation doesn’t occur due to the inability of moisture to escape the wall.

Primers and coatings don’t significantly add to the overall cost of an EIFS project, and the continued use of them can do a lot with regards to convincing customers, homeowners, building owners, designers and architects that the EIFS industry is aware of and is doing everything possible to prevent any further bad press to the material by taking such measures. Using primers and coatings to ensure no future issues can go a long way with regards to enacting community and industry responsibilities and making sure that EIFS is continually known as a reliable, effective product.

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