Q.: When spring comes we want to break ground for our house. The site is almost dead level. The climate is rainy, the neighborhood generally drains slowly, and ponds develop frequently. There will be no basement because it will be a single story house on a slab on ground, but we are concerned that we don't collect water in the yard and especially not close to the house. What should we do about slope on our site?
A.: You will probably want to add fill at the location of the house so that water can flow away from the house in all directions. Enough fill should be brought in to provide a grade that slopes between 1/2 and 1 inch per foot for about 8 to 10 feet in each direction. You may want to slope it farther, but if this causes your house to be considerably higher than the others it may make you unpopular with neighbors who receive your runoff faster.
The bottom of the granular base course for the slab should not be lower than the top of the grade outside the house. The subgrade should be well drained and should be capable of providing uniform support for the slab.
When the house is built, be sure to install drainage such as open gutters or splash blocks to divert downspout water to at least 3 feet from the house.