How to Install Gutter Splash Blocks. Rain, rain, go away, come again some other day. At least wait until the homeowner installs guttering on the house. Having a complete gutter system, including splash blocks, prevents standing water that can damage the foundation or result in damp walls in your basement. It's not enough to have a gutter system for rain runoff from the roof. You have to provide for the downward flow through the downspout.
Determine the type of splash block you want to use. Some splash blocks direct the flow in a straight line from the end of the downspout and away from the house. Others have a broader base and disperse the rain over a wider area; for areas with frequent heavy rains, a splash block with a broader base prevents a hole in the yard at the end of the splash block.
Buy enough splash blocks for your house. You should have one for each downspout.
Install the splash block directly under the downspout. It should carry water at least 3 feet away from the house.
Adjust the angle of the splash block to ensure it slopes down and away from, not toward, the house. You may need to do some digging. The ideal angle is a slope of 6 inches in 10 feet.
Check the downspout when you're cutting grass. Avoid running over it with the mower, as this can drive it into the ground and change the angle.
Redo the earth beneath the splash block, if necessary. The weight of the block and the pounding from the rain will cause it to settle, changing the angle.