As a professional home inspector, I have found that a great deal of the moisture problems found in homes are caused and aggravated by improper grading or as we call it in the inspection industry “negative grading”. Negative grading is where the ground around your home is sloped in towards your foundation. A negative grade allows rain water to pool next to your foundation walls and slowly seep into your basement or crawlspace through the porous concrete walls. And of course where there are moisture issues, mold growth and termite activity is not far behind. Older homes almost always have drainage issues, but even new homes are not immune to the effects of negative grading.
Water is one of the most destructive elements to your home. Water that freezes is extremely powerful and can literally lift a whole house, causing significant foundation damage. Simply piling more dirt around the house in some cases is not the answer. Some houses do not have room below the siding to create a positive slope away from the home by adding more dirt. Covering up the siding with fill dirt or landscaping materials could cause even more damage by rotting the framing of the house. In the case of brick and concrete, water seeps into the porous surface then freezes, cracking and deteriorating the material. Having the dirt too close to, or in contact with the siding promotes wood destroying insect infestations as well. So, just applying more dirt around the home is not always the best remedy.
Proper grading around your home should allow rainwater to naturally flow away from the house without pooling or draining down the foundation wall. The general rule of thumb is to have the ground slope away from your foundation at a minimum rate of 6” for the first 10’. Personally I prefer more of a slope. When it comes to your foundation, the better the slope, the less you have to worry about it. In many cases where the siding is too close to the ground to build up the grade, a French drain would be recommended. This is where a contractor would dig trenches around your home that are sloped away from the foundation. A perforated pipe is laid into the trench and then covered in pea gravel. During rains, the water will enter the pipe and drain far enough away from your foundation as to not cause any problems.
Another common issue related to grading and moisture damage that we see every day is excessive mulch and vegetation that are too close to the home. Mulch and vegetation that is up against the foundation tends to retain moisture and reduce proper drainage. Large bushes and trees can have deep roots that do not let rainwater properly flow away and keep the soil around your home constantly wet. Even a good foundation does not do well under constant water surrounding it. When it comes to mulch and vegetation around your home, less is always better. Vegetation should always be kept at a minimum of 18” away from your home and should never be allowed to touch the home. Trees of any kind should always be planted a minimum of 10’ from your foundation. Personally I prefer farther away. When it comes to trees and your foundation, the farther away the trees, the better for your foundation and drainage.
Installing extensions on all of your downspouts will also help to control the drainage around your home, in a big way. When installing downspout extensions, always opt for the above ground extension over burying them. Downspout extensions that are buried underground may be more ascetically pleasing, however, they will only last for so long before they become improperly pitched by the ever changing earth around us or they become crushed, damaged and clogged with dirt and debris. It will only be a matter of time before the underground extensions fail and when they do, you will have no idea where that rain water is actually terminating. With above ground extensions, you can visibly see the water draining away from your foundation leaving you the peace of mind that your foundation is staying dry. Above ground extensions should always be installed to drain a minimum of ‘4 to 6’ away from your foundation. When it comes to downspout extensions, the longer the better.
A little attention around your home can save you thousands of dollars in repairs if taken care of in a timely manner. Remember that foundation sealing techniques do not address the problems created by improper grading. Even the best most expensive sealers will fail due to the issues created by negative grading. As a home owner, your number one priority concerning your home should always be to keep water away from it. By following these few simple steps you will be helping to keep your most expensive investment nice and dry for years to come.