Foundation problems due to water flow is a common problem and one every home owner should be educated on. If you think about it, a typical home display a 2,000 square feet of surface to the sky. All the rain that lands on that surface runs down into a gutter and out a few downspouts. A typical eight inch Seattle or Everett February rainfall drives 10,000 gallons of water down your drains!
If your gutters are clogged, you are putting all that rain directly at the foot of your foundation. Foundations can fail when there is either too much water under the home or too little water. It is worsened by variations in water saturation under the home. The soil under the foundation contracts and expands depending upon the amount of water in the soil. Increased water will cause the soil to heave and stress the foundation. Lack of water causes the soil to shrink and settle allowing the foundation to fall.
Foundations can dry out when plants are placed too close to the home, especially trees. Roots running under the foundation suck water out creating dry spots. Trees should be planted at least 5 feet from the foundation. Many other factors can cause variation in foundation saturation level, but the biggest controllable variable is the water coming off your roof.
A few simple guidelines will keep your situation in good order. First is to clean your gutters twice a year: spring and fall. Don't wait for all the leaves to fall. If you have an excess of trees around your property you might want to add a third gutter cleaning. Don't rely on gutter guards to protect you.
If you do use gutter guards keep two facts in mind. First gutter guards restrict the flow of water into the gutter and may result in overflow in heavy rain. Make certain your gutter and gutter guard system is sized appropriately. Second thing is to not set and forget your gutters when you have a gutter guard. Indeed, your gutters may be good for 5 years or more with these guards, but debris will accumulate in the gutters. Worse is that you can't see the build up because of the guard cap. Make sure to regularly check your gutters even with gutter guards and make sure they are free flowing.
Make sure your gutters are in good shape without leaks and breaks. Make sure the downspouts are not clogged and there are no breaks. Finally, make sure that the drainage where the downspout stops is away from the home and that the water flows away. If you have underground drainage make sure that drainage is working properly. Periodically simulate a rain storm and gutter drainage by placing a garden hose in the underground gutter drain system and make sure it flows freely.
If you take care of your gutter system and do these simple precautions you will help protect your home's foundation.