How do I look for yard drainage problems when buying a house?
Sunday, January 31, 2021
You might get lucky and visit a house during the rainy season or after a thunderstorm and find areas of standing water and soggy soil—like in the photo above. This makes it easier to figure out some, but not necessarily all, of the site drainage problems a house may have. Here’s a list of questions to answer as you walk around the property:
• What is the “lay of the land?" Building codes require that the ground on all sides of a home slope downward a minimum of 6-inches in the first 10-feet away from the house. So homes today are always built on a raised pad of soil that keeps water from collecting around the foundation. When the house is closer to the property line than 10 feet, or walls or other barriers prevent compliance, drains or swales must be constructed to ensure adequate drainage away from the house. This typically happens at the sides of houses on a narrow lot. See our blog post How much is the ground required to slope away from a house? for more on this.
But it wasn’t always that way. Older homes were often built with ground sloping towards the house on one side and away from it on the other. This forces both surface and ground water to run around the house or under it. Homes near the bottom of a hill with this configuration will have the worst problems.
• Any signs of previous standing water on patios, walkways, or driveways? Because standing water collects debris and stains the surface over time, it can be easy to spot. Surfaces should slope about 1/8” to 1/4” per foot away from the house and have no flow obstructions at the lower edges.
Inadequate slope, lack of drainage openings, or clogged openings at the base plate of a screen porch also become obvious this way.
• Does the house have gutters? Gutters perform the important function of moving roof water away from the foundation, and a fully guttered house is a definite plus. But the downspouts should have extensions with splash blocks that terminate several feet away from the foundation in order provide effective rainwater control. If not, they end up creating a small pond of water next to the house after a heavy rain, which is arguably worse than no gutters at all.
• Any washed out areas or an exposed house foundation? These are both indications of soil erosion. Exposed tree roots and leaning retaining walls or posts are other signs of problems.
• Mushy, soft ground under foot? This may be temporary, due to a high water table during an extremely rainy season, a low spot in the yard where water collects but doesn’t drain quickly, clay soil, or areas of compacted soil with low permeability. There might be pockets of oozing mud or low standing water visible in the grass.
Your home inspector will also be looking for these signs of site drainage problems, and can give you an insight into likely causes and cures.
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Here’s links to a collection of our other blog posts about a home’s SITE:
• Which trees are most likely to fall over on your house in a hurricane?
Visit our SITE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.
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How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
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