This is another example of how building knowledge accumulated over decades by older builders is lost. All one has to do is walk through older neighborhoods in just about every major city east of the Mississippi River to see what builders of old knew: The top of a foundation should never be near the soil line or grade.
Look at houses that were built in the late 1800s or early 1900s. You’ll notice that the top of the foundations of these homes almost always sat a good 30 inches or more above the grade. The houses had wood basement windows, and the bottom of their sills were about 6 inches above the level of the surrounding soil.
This method of construction allowed light into basements and helped preserve the wood that was used to build the house. The wood framing was far away from splashing water and creeping damp. Creeping damp is the phenomenon of water being pulled up through masonry construction against the tug of gravity by water’s capillary attraction.
For some odd reason, builders these days tend to ignore or to have forgotten what the builders before them discovered.
If you look at the building code, you should realize that it’s not just a collection of minimum building standards; it’s a moving target — in a state of near constant change. Codes from not too long ago said that you need at least 6 inches of foundation showing above the grade. What’s more, you need at least 6 inches of fall in the soil in the first 10 feet of horizontal distance away from the house. Remember, this is a minimum standard.
I used to make my foundations, when possible, about 18 inches higher than the surrounding grade. Using the dirt I dug from the basement, I then was able to make a long gentle slope away from the foundation so that the ground around the house appeared level, or nearly so.
The builder who built my wife’s childhood home did an excellent job of this. This house sits about 70 feet from the curb of the street and the front yard looks dead level. But guess what. It has about 24 inches of fall over that distance! I know because I checked it one day using a very accurate builder’s level transit.
The builder of your house should have done the same. In fact, it’s possible you have quite a bit of fall now, but your eyes are playing a trick on you. Get access to a laser level or transit and check to see how much fall you really have from the top of your foundation to the city sidewalk or street curb.
If you can’t get your hands on one of these precision instruments, you can use a standard 4-foot level and some wood stakes of increasing length with a flat top. Using these things and a four-pound hammer, you can start to determine how much fall your front yard has from your house to the street.
Place one end of the level on the top of the foundation. Drive a stake in the ground at the other end of the level so that when the level rests on it, the bubble in the level is centered between the two lines on the vial. Now move the end of the level that was on the foundation to the stake. Drive a new slightly longer stake into the ground for the other end of the level to rest on.
Repeat this procedure using longer and longer stakes until you reach the street curb. If you did everything right, the height of the last stake sticking out of the ground closest to the road tells you how much your lot has fallen away from the house as you get closer to the roadway. My guess is you’ll be shocked at how much fall there is.
The other thing to watch for is creating a depressed area between your home and any sidewalk that leads from a driveway to your front door. All too often I see ponds in between these sidewalks and the house because the sidewalk acts as a dam and doesn’t allow surface water to drain away.
The best way to prevent all these issues is to keep the top of the foundation at least 18 inches above grade. You can even go up as much as 24 inches. Creative planning then can make it so there are minimal steps to get up into the home.
As for how much mulch one should put up against a house foundation, I say use the minimal amount. Keep in mind that during dry spells the mulch can be flammable and cause a house fire if it somehow ignites.
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