Rainy days are some of the best days to learn about houses and neighborhoods. Why? Drainage issues are the number one reason for foundation issues on a home. Foundation issues are one of the most expensive repairs a seller or buyer can face when selling or buying a home.
Most of us do not go under our houses and crawl around the crawl space to keep track of our foundation. I certainly am not interested in that job. However, keeping an eye on your crawlspace, especially on a rainy day, can prevent repairs down the road. Making sure that the crawlspace is "dry as a bone" is one of the most comforting feelings one can have after a little El Niño month.
The first step to protecting your foundation is making sure gutters are clean, water is flowing, and more specifically water is flowing away from your home and foundation. Water standing around the foundation of your home will certainly penetrate and eventually deteriorate the soil enough to cause settling and/or concrete deterioration. Proper drainage can be as simple as installing downspout directional tubes and as complicated as installing a french drain. If you are going to install a french drain, be very sure you know what you are doing. It is not as simple as digging a trench. The proper slope is absolutely critical to a proper french drain. I have seen several homes where a owner was taken by surprise to realize the french drain that they had built actually placed more water at the foundation.
If you, or your inspector are not under the house on a rainy day, there are ways to look for previous water issues. Look for efflorescence on the concrete walls of your basement or foundation. The white, powdery looking lines, marks are evidence that water has been in contact with the concrete and has left some minerals behind as evidence. This does not necessarily mean that there is water pouring down every rainy day but it is the first flag to further investigate.
At this point, the home inspector will also make note of any cracks seen in the concrete under your home. There are different types of cracks, varying descriptions, and related repairs to said cracks. Realize that the property inspector is not a foundation expert and will state in the report that an "appropriate professional" should take a look. Foundation inspections can be the death of deals because structural experts never make light of anything.
Which leads me to my next observation. I have seen both sellers and buyers decide not to complete a foundation inspection because it "costs too much". Depending on where the home is located (on the valley floor or on the side of a mountain) foundation inspections can range from $500 to $3000. However, the average home price in the Santa Clara County is $632,000 and all homes face the risk of some shaking during their lifetime due to seismic activity. If you really like the house, make sure it is as structurally sound as it can be. If you really want to sell your home, understand the cost of fixing foundation issues.
Rain is a good thing. Our earth needs it but our foundations don't. If your agent encourages you to see houses in the rain, recognize that they are not crazy. All we need is an umbrella and maybe some rain boots and we are set to find the right house for you.