Waterproofing Concrete Foundation Systems and Your Home's Energy

You might think that waterproofing concrete foundation systems may not be related to energy efficiency, but if you are going to upgrade your basement or foundation insulation, and seal all cracks and holes, then overlooking waterproofing will be undermining all your hard work.

One crazy thing about concrete, our most basic, easy-to-concoct and reliable load-bearing medium: not only does it have lousy insulation value n(R-Value of 0.5), it also loves moisture - different mixes have different porosity, but under the right conditions, foundation concrete can act like a giant sponge. Go to House Mold and MildewIf you have mold in your house, and need to deal with it in your basement

Like the roof, moisture plays a huge part in the foundation's welfare, especially since all water touching the house goes straight into the ground surrounding the house, and can cause organic debris and rot next to the foundation. Properly operating drainage systems should be part of any waterproofing concrete foundation project.

I am a big fan of gutters as well as a good drainage system. Most of my architect friends and colleagues don't like the look of gutters; but I don't know many other affordable solutions that direct water away and avoid moisture and rut (note to self: decomposing organic matter next to foundation - very bad).

Below, is an all-telling diagram of a typical home, and all the waterproof concrete foundation methods available to draw moisture away from the exterior of a house. This picture came from All-Phase-Renovations in Houston, TX, and seems to really have their act together; I only wish they would serve the Northeast U.S.

In general, your home should have drains in the foundation footing, since concrete tends to wick moisture into itself; once moisture sets in, you would not see or even know about it, until the rot surfaces. For most of us, this level of exterior waterproofing will require professional help. If you have water issues, consider one of the following steps:

  1. Take a good look at this diagram, and study the potential water entry regions that are indicated.
  2. Go into your basement and look at any water trails or stains that can point to the potential areas where water can be entering your home.
  3. Go outside, walk around your house and check the following: the slope (hopefully slanting downward from your house), any standing water near the house (maybe from disconnected gutters?), rotting vegetation, etc.

Once we have done everything reasonable and feasible to waterproofing concrete foundation walls, we can waterproof the interior walls of the foundation.

Waterproofing Interior Foundation Walls

To start, remove any paint from the wall and clean the wall; if this is not easily done, then you will have to waterproof the exterior wall. Buy a cement-based waterproof coating from your home center along with a tampico brush; note that many coatings will require a bonding agent also. From here on, use the manufacturer's instructions for use.

Just a note to those of you who paint decoratively using the strie (or dragging) technique. The tampico brush is also frequently used for strie'ing - it is a china bristle brush. For waterproofing concrete foundation walls, you would apply a brushable coating with the brush, working it into the pores with a semi-circular motion, then smoothing it evenly on the surface.

Do this first for a small test section and when you know that the coating does actually adhere, work on the rest of the wall in small sections. Let the coating cure for the required time (mist it once in a while to help it dry evenly). To see if the coating has adhered, take a cold chisel and a hammer and see if you can shear the coating. If the coating shears off, then either clean the wall and recoat. If that doesn't "take" either, waterproof the exterior wall in warm weather (this is when I would enlist some help).

My Final 2 Cents: Know Your Land

The ground that supports your foundation is very important to its longevity. Know what your topography is; for example, is your land rocky, silty and sandy, or is the soil really dense like clay? Your soil's density, porosity, seismic stability and how well it is compacted are very important to the stability of your foundation.

Right about now, it should become clear how everything inside and outside your home interacts as a system. In other words, cutting corners when building a foundation is not a smart idea - fixes after the fact can be complicated and VERY costly, especially, if there are ground-settling issues, causing the foundation to crack.

Next, read and download my .pdf guide,Visual Evaluation of Your home foundations - A simple guide that summarizes how to evaluate the condition of your foundation. This guide shows the issues to watch for when dealing with exterior repairs or improvements that are energy-related.

Read more about Examples of Energy Efficient Foundations - I show pictures and talk about problem basements and how they were resolved.

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