MDI Building Science 101: Water Management
One of the hardest problems to fix is below ground water intrusion. This is a major aspect of building long lasting structures which consists of a two-part system to effectively control moisture movement.
Step 1: Moisture Management around the exterior of the foundation
Starting from bottom up:
• We install perforated pipe at the bottom of the foundation so that water can infiltrate into the pipe before it gets to the most susceptible area of the foundation, the “cold joint”, which is where the footer meets the frost wall.
• The pipe is placed on a slope to give water a path of least resistance away from the building.
• Filter fabric prevents the pipe from getting filled with fine particle sediment over time.
• Then the surrounding area is back filled with drain rock (to the orange line on the wall) to provide air space between the drain rock which allows ground water to move freely away from the foundation.
This process helps to reduce the amount of ground water that can surround the building. And in turn this helps to reduce hydrostatic pressure on the foundation that would otherwise be produced by water logged tightly packed fine sediment soils.
Step 2: Foundation Water Proofing
• This consists of a hot applied elastometric asphalt emulsion applied to the foundation walls. This product has “2000% stretch capacity” per the manufacturer’s specs.
• Next, the foundation is deliberately hit with a flood coat on top of the footer, so the heaviest and thickest portion of waterproofing is over the cold seam.
Managing groundwater on the landscaping level before it surrounds the home is the next tier to this process on the exterior. And installing drain pipe inside the foundation is a different part of the system on the interior, but the steps above are the basics to managing moisture directly around the exterior of the home.
This process is all too often underdone. We believe that overlapping and slightly redundant systems together make up the best building practice for water management, above and below the ground. We follow the same school of thought with our interior water management systems.
Here’s a little taste of exterior water management (or lack there of) from our own Glacier National Park (photo: Martin Brechtl)