House-Flipper Guide – Part I: Drainage

Drainage, better known to house flippers as landscaping, is the first in our series of articles to help guide DIY real estate moguls away from the “function follows form” model of home renovation.

We understand that there is confusion between drainage and landscaping; it’s hard not to notice the lush foliage on the cover photos of all those Do-It-Yourself books, magazines, and websites. But trust us when we say there is something very important directly beneath all that shrubbery.

Let’s start with the basic principle: “drainage” is the word we commonly use to talk about which way water flows once it begins to collect on the ground. This “water” typically comes from three different sources: rain or snow (the weather), irrigation, and in some instances from beneath the ground itself (subterranean moisture).

Drainage is completely dependent on gravity, which fortunately for all house-flipping purposes is a constant. Water will always flow downhill unless some sort of mechanical/electrical device is introduced in the water path or collection point, these devices are known as sump-pumps. However, as we will demonstrate, the need for a sump-pump is exactly what we are trying to avoid. The presence of a sump-pump in a basement or subarea of a home is all the evidence a home inspector needs to note a failing drainage system.

The ultimate goal of a proper drainage system is to drain all moisture, surface and subterranean, away from the building and toward a municipal drainage system or natural waterway.

The reason for proper drainage is that to allow moisture to find its way through a building rather than away from or around the building is bad for the building. It’s bad for the building much in the same way that a roof leak is bad for the building.

Google the term “moisture intrusion” and select “images” for more information and motivation.

So there are several general points to consider:

  • First, the existing slope of the site and the home’s relation to it. Tract homes built within the last 40-or-so years probably had good drainage immediately after construction. They may still have good drainage. That means the house was built high enough above the overall soil grade of the site to allow for drainage away from the building. There’s (again, probably) also a storm-drain system, natural or man-made, where surface water can drain to. Most often this is simply street gutters. This is the best case scenario for the house-flipper because any corrections of the drainage system that might be needed will most likely be minor corrections, e.g. re-grading planters and lawn areas.Where things get difficult is at some older homes and homes on hillsides. There are many older homes that have foundations that are too low and too close to, or even below, the soil grade to achieve any slope directed away from the building. Homes on hillsides will have great drainage on one side and complicated drainage on the other.

    There is no simple answer to dealing with subterranean moisture. You will need to consult with an engineer because subterranean moisture doesn’t necessarily follow the laws of gravity and its source can be a mystery.

  • Second, paved areas such as driveways, porches, and walks. To have good drainage, the pavement around the building also needs to slope away from the building. Perfectly level patios are wrong, or defective, or incorrect, or substandard, or whatever the favored term might be of the home inspector hired by your prospective buyers. The trick with bad drainage on pavement is that it’s rarely correctable. The correction is remove and replace.
  • Lastly, the roof. Roof drainage can have the biggest impact on site drainage. Roof gutters are ideal, but keep in mind that those gutter downspouts need to terminate in places that have really good drainage. A downspout that dumps into the planter with poor drainage is significantly compounding the problem.

For some homes, proper drainage requires nothing more than basic and knowledgeable gardening, other homes require complicated and expensive engineered systems. Every home is unique and there are many factors that can have an effect on drainage.

Just remember: landscaping is the “form” and drainage is the “function.”

Go to Part II: Roof


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