Over many years as a real estate broker I have occaisionally been called out to a clients home for problems with moisture on the basement floor and/or heaving of the basement floor concrete slab. Almost one hundred percent of the time, the reason for the problem was improper drainage of water around the exterior of the foundation wall. Home builders over the years have made great improvements for avoiding these problems for the homeowner, yet everything still boils down to the owner maintaining a positive ground slope for water to drain away from the foundation. The swelling soils in Denver, often referred to as bentonite clay, can expand with tremendous force when they become saturated with water. Typically it is good to have at least a six inch drop from the foundation to six feet out to cause the water to drain away from the foundation. In this area, or border, you will normally see rock, bark or mulch with a few shrubs or bushes that need a low amount of water. So, the heavier watering of the grass is outside this border thereby minimizing any water around the foundation.
The torrential rain in Denver last night provided a perfect opportunity to see if your drainage was working properly or if you were getting pooling of water at the foundation. Over time, such things as the settling of backfill dirt around the foundation, dogs digging out a cool spot to nap next to the foundation and dug outs for flower beds can cause the slope of the ground to be back toward the foundation. Negative slope toward the foundation is an absolute no, no!
While I was out last night checking my drainage after the rain let up a bit, I made sure that all downspouts were in the down positon and that underground drain lines were draining freely at their point of termination in the yard.
My home has a structural wood floor, not a concrete slab floor. I have crawled every square inch of the craw space under the basement floor shortly after we moved in and after a very, very heavy rain storm to make sure the dirt was dry around the interior of the foundation.