Investigate Water Intrusion

Water intrusion is one of the biggest problems for any building. In a wood-framed home with fiberglass insulation, water/moisture can be absorbed into these materials and remain there for a long time, resulting in the development of mold and decay which can cause an unhealthy indoor environment. The big advantage of ICF walls is that they do not promote mold or mildew and will not rot or decay. But the big question is, why would an ICF wall assembly leak? How would water make its way through a solid concrete wall?

Every ICF wall, either below grade or above grade, on the exterior side, must be covered with a water-resistant exterior finishing material. On below-grade walls, a waterproofing and or dampproofing application is required along with a perimeter drainage system. At grade level between the waterproofing application and the exterior finish, approximately 16 inches to 24 inches, a water-resistant coating, typically a stucco based material or equivalent material, is applied. The above-grade wall can have any type of exterior finish. If the finish is wood, an air space is required behind the siding to allow the product to dry, and to allow any moisture to run down the EPS wall face. Masonry finishes have a similar air space with base flashing to direct the moisture over the foundation application.

In every one of these applications, the finishes must be lapped, like roofing shingles, allowing exterior rainwater to drain down the face of the wall, over each finish, to the lowest level into the perimeter drainage. Flashings are very important above openings, especially along the top edge, to prevent water from entering the window, door or wall. Maintaining the direct flow over the exterior wall face and around openings is a critical building trait.

The first thing in investigating water intrusion is to follow the basic rule that water runs downhill. Even if you discover water in the basement, start the investigation at the top of the wall. Do all the openings have flashings along the top that divert the water over and around the opening? If any water gets into the wall assembly at an opening, it will travel down to the lowest point. Next, all the exterior finishes must be installed. All the openings including doors, windows, and service penetrations must be sealed on all sides, plus have sealed flashing along the top edge. Check the exterior for any holes or unfinished areas around openings.

Next, check around the perimeter at all grade levels. Are there any cracks or holes in the perimeter finishing material? Does the grade slope away from the wall to eliminate any ponding against the wall? Are the downspouts directing rainwater away from the foundation? One of the main things to look for is the overlap of the perimeter finish over the waterproofing membrane. This prevents any water draining down the wall from getting behind the top edge of the waterproofing membrane.

The hardest part to investigate is the below-grade waterproofing. First, was the material used compatible with EPS and the ICF manufacturer? Was it a spray-on application or a peel and stick membrane? There are many factors that could influence the application and operation of below-grade waterproofing systems. Was the wall prepped properly, with gaps filled and broken edges fixed prior to the application? Was a primer used, if recommended, for the peel and stick membrane? Was a protection layer specified or required over the membrane? Was care taken during the backfill stage to protect the membrane and not allow stones or debris to puncture it? Any damage here would allow for water intrusion. Another factor is weather and UV rays. When was the waterproofing installed? Hot or cold weather influences the adhesion. Also, if left exposed too long, UV rays will start to deteriorate most applications (check with product manufacturer).

The EPS of an ICF does not absorb water or moisture. ICF blocks are designed with a unique interlock that acts as a water stop along each horizontal joint. Plus the vertical joints have a built-in water stop seam. If water is allowed to get behind any of the exterior finishes, it may, over time, seep through the EPS layer and into the concrete. Small amounts of moisture will be absorbed into the concrete and dissipate over time. Within the ICF wall, as the concrete sets and dries, there may be a minute seam between the inside face of the EPS and the concrete. This seam would allow any substantial water intrusion to travel down the inside face of the ICF wall to the lowest level. This is one reason the exterior wall face must be built to resist water intrusion and allow for continuous drainage.

As with any wall construction, the main goal of the design is for the proper attention to detail, not only in the selection but in the application of materials. The next stage is the attention to flashings and exterior sealants. The waterproofing industry has developed many approved below-grade applications for ICFs. One of the biggest mistakes made by ICF builders and DIY homeowners is to skimp on the waterproofing materials or applications. Lesson learned the hard way is that the cheapest may not be the best application, resulting in big repair costs down the road.

The “how to”investigation really starts during the construction phase. If you have the ability to check and monitor material applications, flashing, sealants, etc., you will be ahead of the game. As an ICF contractor, this should be second nature. If, as a homeowner, you move into an ICF house, do a visual check on the exterior for proper flashings, seals, overlapping materials, and grades sloping away from the house.
ICFs are an excellent building material for creating a healthy, high-performance building envelope. Investigating the rare possibility of water intrusion will result in finding a fault somewhere on the exterior finishing materials or applications above or below grade. Built following construction standards, any home or building should not experience water intrusion.