Guide to Proper Home Drainage Systems

By Murray Anderson

A cool, damp basement, musty smells, and maybe even mold or mildew on the walls are all indications of moisture getting into your basement. The main cause is likely poor drainage around your home that allows moisture to build up and remain in the soil around your foundation, and then work its way right through your foundation and into your home. Fixing drainage problems around your house can be a relatively inexpensive proposition, and they often come down to a couple of causes - how rainwater is handled and the grading or slope of your property.

Handling Rainwater

Gutters (or eavestroughs as they called in some parts of the country) are an important part of the drainage system around your house. If yours are nonexistent or in poor repair, or if the downspout empties right beside your house, they could be causing the problem.

Gutters need to be installed properly so that they will catch the water coming off your roof and channel it away from your house and foundation. Gutters should be installed with a downward slope of 1 inch for every 2 feet of run to ensure they drain completely. If your house is more than 35 feet wide, the optimal installation would have the gutters sloping down from a high point in the middle to a downspout at each end of the house.

All gutters need to be firmly attached (screws are best, since they won't back out over time) with the center of the downspout aligned under the lip of the roof. Gutters can be made up of sections of trough (usually 10 - 12 feet long), or installed as a long continuous piece up to 37 feet wide. If yours are in sections, make sure the seams are well sealed and water doesn't leak through. Gutters that leak are a problem not just because they drip water on your head, but because the drips land close to the foundation.

A downspout diverter directs water flowing from the downspout onto the driveway where it can't seep into the ground around the foundation. A hinge for this downspout would also help to get it out of the way of yard equipment.

Downspouts need to be large enough to handle the large amount of water that can come running off your roof in a heavy rainfall. The minimum size for a downspout should be 2 x 3 inches, but a larger size (like 3 x 4 inches) is even better. The larger size makes it less likely that anything will be able to block the downspout - even a tennis ball will drop right through, and you know water won't back up into your gutters during a heavy rain and possibly overflow.

At ground level, the water from your downspout should be directed at least 5 feet away from your house. It's best to have the water flowing onto a hard surface (like a driveway) or a fiberglass or concrete splashguard designed to spread the water and stop it from puddling on the ground. Flexible plastic diverters or hinge attachments for your downspout allow you to swing it up out of the way when cutting your lawn, so you're not constantly tripping over the downspout.

Proper Grading and Slope

Once the water is on the ground, it's important that it doesn't just sit there. This is where the grading of your property is important. Most building codes require that the ground around a foundation slope away from the foundation at a minimum of 6 inches in the first 10 feet and with another foot of slope in the next 100 feet. (This is a minimum - more slope will obviously help get water away from the foundation faster). Don't change the grading of your lot, and if you notice some low spots developing, be sure to fill them.

If you have a problem with water constantly accumulating in a particular area, you might consider installing a "French drain." A French drain is a small trench with a perforated pipe surrounded by sand or gravel that directs the water flow away from the foundation following the grade. Not only will it get the water away from the house, it will do it without any possibility of water runoff damage or erosion.

Part 2: Taking Care of Your Drainage System >

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Murray Anderson is an experienced freelance writer with articles published in both the United States and Canada. He has written on a wide range of topics, but specializes in home maintenance and how to's.

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