Stormwater infiltration can destroy a building over time and make an otherwise sustainable design un-sustainable. We receive hundreds of calls each year from homeowners and real estate professionals complaining about water infiltration. In almost every case the caller has no clue about the cause. The best guess is usually that there is some kind of wet weather spring that has suddenly appeared out of nowhere to wreak havoc upon the hapless homeowner. Is this really an unforeseen calamity with nothing to do with an otherwise perfectly designed drainage system? Not likely.
Wet weather springs are not the problem. In most residential subdivisions, there is no integrated drainage design for individual homes. Bad things are bound to happen: wet basements and crawlspaces, mold, and dry rot. Sometimes problems manifest themselves immediately, but more often, the homeowner begins to notice the symptoms weeks, months, or even years after construction. One thing is for sure: these drainage deficiencies are not accidents but predictable outcomes of bad design. And once the homeowner discovers the signs of water infiltration, some of the most preposterous solutions are offered and actually implemented.
We categorize them as follows:
Build a moat – If you think of your home as your castle, you can dig a deep trench next to the foundation, install a perforated plastic pipe, and fill the trench with gravel. This will invite all the stormwater in the neighborhood to come right up to your foundation wall. You have just constructed a moat for your castle.
You say, “No problem. I have the pipe in the trench to drain the water away once it reaches my moat.” I say two things: 1) the pipe will deteriorate and fill with debris in short order and 2) for the water to drain, there must be some standing water to drive the flow. (Remember Hydraulics 101?)
So what you have really done is to pay someone thousands of dollars to destroy your landscaping and make the problem permanent. Believe it or not, there is a huge industry installing these systems all over the country.
Invite the water into your home – Maybe even worse than the moat idea is to install a trench inside the foundation wall to collect the infiltration and pump it away. We call this the NeverDry System. (Get it?) There are a number of problems with this one but probably the most offensive from a building science perspective is the constant erosion around the foundation as we encourage perched groundwater to flow into the building. Other problems include the creation of a direct conduit for the infiltration of radon and moisture. The sump surrounding the perimeter of the basement is also a haven for mold, bacteria, insects, and other vermin.
So what is the right way to fix a water infiltration problem? The obvious answer is to design the stormwater management system correctly and integrate it into the construction of the building. From our experience, this would eliminate 90% of homeowner complaints and save untold millions of dollars in often counterproductive repairs.
There are four basics that, if followed, will practically guarantee a water-proof home:
- Install the proper size gutters and the appropriate size and number of downspouts.
- Keep the gutters free of debris.
- Get the water from the downspouts away from the foundation and keep it away.
- Install clay or an equivalent water retardant material next to the foundation.
- If there is a regional flow of water toward the building, install a curtain drain well away from the foundation so that water never reaches the building wall.
Finally, it should be stressed that sub-standard drainage is not just an issue in residential construction. Some of the same misguided principles are at work in commercial construction as well.
If we want to create sustainable structures, we must remember that old thing about the definition of insanity. Regardless of what anyone says, whatever we are doing today is not working very well. The key to overcoming bad habits is to forget how we have done it in the past and evaluate what really makes sense. The payoff comes in longer-lasting, healthier buildings, and fewer headaches from trying to repair problems that never should have been.
Contact: Barry Westbrook
4014 Flagstone Court
Franklin, Tennessee 37069