Water Drainage and Your Home Design
I can remember when it would rain and sometimes water would show up on our basement floor and my parents would try their best to mop it up. Water is one of the most intrusive elements we live with in a home. One of the very basic functions of a home is to put a “roof over our head”. What does that mean ? Well, it means that a home provides us a safe hideaway from the elements of weather. And one of those is water. Water can damage a home’s structure and its finishes. Water if allowed to gather inside a home can promote decay and disease even. So keeping water out of a home is one of the most important things an Architect or architectural designer has to design around.
One of the ways water can enter our homes is from the parcel of land we purchased. Designers, engineers, architects and building officials refer this issue to the topic of site drainage. Does the site have a natural way of allowing rain and snow melt to run off and away from the building? Or does it gather the water into pools and slowly removes the water by soaking it into the ground itself? Or is it a combination of the two?
When you want a custom home built, you want that home to be safe from the destructive effects of water. And so one of the crucial pieces of designing a home is how water on the ground is kept from damaging it. I am amazed at how this one item can effect the home’s design. It effects how high the home is built relative to the existing ground. Which if there is a “height restriction” on the home relative to the existing ground, then the design required height of the floors do to site drainage could result in a home with limits on roof pitch and the total area the home takes on the ground. And those in turn can limit design styles that work. And so site drainage is an important part of how the land effects the home.
In order to keep surface water from entering a home, there are three basic areas of design that need to be addressed. First is the basic need to keep surface water from moving up to the home. Good home designs address this through a use of roof gutters and down spouts that route water from the roof of a home and release it on the ground at least five feet or more away from the exterior walls. That water is prevented from flowing back to the home by having the “grade” or the finished surface of the ground shaped in a way that water that gets on it flows away from the home. Planning and Building Safety departments may as they have along the Front Range of Colorado require a perimeter system of surface membrane and rock extending out on the ground for the first five feet from a home. This buffer area is sometimes limited in its use for plants, bushes and trees. Many jurisdictions with this required buffer do not allow plants of any sort in this area in order to prevent owners from needing to irrigate any portion of this buffer.
The second area of design is not so visibly evident. It is what is called waterproofing or dampproofing of the exterior side of the foundation wall that is covered by soil. Water that gets under the surface of the ground by soaking into it can flow back to the foundation. A foundation is by itself not able to keep water out of a home. Concrete and concrete block systems are permeable to an extent. Water can penetrate the surface and it soaks into the concrete or block. Once the foundation is saturated, the water will start to weep out of it into the inside of the home. And any cracks or fissures in a foundation will become pathways for water to get into a home. A preventive measure for this intrusion is a system of dampproofing and or waterproofing. This is basically a membrane coating that is applied to the exterior face of the foundation wall below the ground that is less permeable to water. Water gathers on its surface and can flow down to the third area of design, which is the perimeter foundation drain system.
Once water that gets to the exterior of a foundation is diverted downward, it still needs to be removed before it gets under the foundation wall and flows up the other side into the home. And we call this system a “foundation drain”. It is a system of pipes that is at the level of the bottom of the foundation that has holes in it to allow water to gather inside. The pipe is surrounded by rock which is covered by a water permeable membrane that allows water to get to this drain pipe without allowing the dirt to move in and plug things up. This drain is then usually tied to a plastic pit called a “sump pit” that the water can flow into.
Once the sump pit has water in it, a submersible water pump then activates to send the water back up an ejection pipe that is then routed to a point of discharge safely away from the home.
When these three systems (A system to divert surface and roof water from flowing up to the home, a system of waterproofing or dampproofing a foundation, and the perimeter drain system) are designed well, most water can be prevented from entering a home and causing damage.
Can water still invade by overwhelming these systems or finding other ways to get in? Absolutely. These systems are not a guaranteed cure all. And should never be thought of as such. This is only basic to getting some protection from water. Some sources of water, such as a rising water table in the ground, or an underground stream to name but a couple can be nearly impossible to control. Even with more extensive systems such as concrete “admixtures”, and membranes under foundations and concrete floors, and water stops that are cast into the concrete can be very expensive additional items. They may or may not work. Remember water will flow into an area of least resistance. And the very best beginning point to keep water out is through the three main design areas of water control.
Keeping water from flowing up to a home in the first place is paramount to preventing this intrusive element from doing damage. Note how the land handles water in the first place, and then raise the home up out of the ground and slope the grade so that water does not have a chance to get up to the foundation and you will be more apt to keep water out.
Gary Miller
Principal and Architectural Designer,
Timbertree and Stonecastle Designs, LLC
Next Week’s Blog Subject: Your Land and its Natural Habitat Issues