Water Management for Homes

Water ManagementNo matter where you live water is all around us.  Some parts of the country more than others, but either way we design homes to keep the weather out.  Water management will always be a big part of the building process.  Unfortunately it does not always get the attention it deserves.  Water is the most destructive force on a home, by far.  It causes problems quickly or creates long term problems that you don’t even know are happening.  It can cause leaks that are found immediately or deteriorate a home slowly.  Water issues can affect to a building in both liquid and vapor form.  Liquid water is the one with think of the most, such as roof leaks, basement leaks or window leaks.  Unfortunately there are many ways water can destroy a home.  The movement through the building happens in 4 ways.

  1. Liquid flow – This is done by gravity and air pressure differences.  Water will flow into the buildings cracks or holes.  Common examples are roof leaks, plumbing leaks, basement leaks and window leaks.
  2. Capillary movement – Moves through tiny spaces within building materials.  Such as wicking up a wall from a leak.  Or drawing water from the ground.  Yes water can move up.
  3. Air movement – Air carries water vapor and as it moves the vapor moves with it.  Air pressure differences is the force that drives the movement of vapor.  When the air reaches saturation, called the dew point, condensation will occur.
  4. Vapor diffusion – Water vapor will move through solid objects at a rate that depends on their permeance and the pressure differences.

As a builder we need to think of all these different forms of water movement through a building.  We can’t stop water, but we can control it.

How do we control water?

For a homeowner, you have limited options since your home is already built.  First and foremost, make sure you have gutters and downspouts and that they are draining the rain water at least 6 feet from the foundation.  Make sure your grade is sloping away from the foundation and not back into it.  Make sure you monitor the indoor relative humidity level.  Make sure your bathroom fan is vented directly to the outdoors and run it at least 20 minutes after you shower.  Fix any plumbing, windows and roof leaks immediately.  Maintain your home on a regular basis and be aware of what is happening.

As a builder, your responsibility is somewhat different.  You need to design a home with water management as a top priority.  Unfortunately this doesn’t happen as much as it needs to.  Here is a basic list of things you, as builders, need to consider when designing your homes.

  1. The roof design of the home needs to keep rainwater management in mind.  Some of the roof designs that we see on larger homes these days are just awful when it comes to managing water.
  2. You need to design the gutter and downspout system that can handle the water load and distribute it away from the foundation.
  3. Flashing details need to be thought through and installed properly.
  4. The building shell needs to have control layers built in to manage the water.  Siding is not water proof.  Water will get behind that siding and needs to drain out and be able to dry.
  5. Grading needs to slope away from the home.
  6. Foundation should have some type of water or damp proofing.
  7. Drain tile along the footings needs to be designed and installed properly.
  8. The wall assembly (framing, insulation and air sealing) needs to be designed to manage water.  We need to make sure moisture doesn’t get trapped in the wall and if it does it needs to be able to dry out.
  9. Air sealing needs to be done extremely well.  We need to keep that warm air from leaking into the wall cavity and meeting the cold side.  Insulation and air sealing will manage this aspect.
  10. Relative humidity needs to be controlled throughout the year.
  11. Mechanical ventilation needs to be available to control the amount of fresh air the home is getting.  As homes continue to get tighter, this is a very critical piece of the puzzle.  The home needs to breathe in a controlled fashion.  HRVs and ERVs are wonderful technology and should be a part of every new home.
  12. We need to use the proper insulation on the foundation and avoid insulation types that don’t do well with moisture.

Again this is just a very basic description of what needs to be considered when a home is being designed.  If you are a homeowner that is working with a builder, you also need to be aware of these issues and ask the builder how they are addressing them.  The margin for error on new construction is getting smaller.  We have to make sure we are considering the building science aspect.  This is why it is so important to consult a building science expert when designing a home.