Share:

When you’re in the site preparation stage of building a home, drainage is one of the most important factors to consider. Failure to evaluate how you’ll deal with rainwater runoff can lead to larger issues later on. Learn more about positive and negative drainage using the guide below.

What Is Positive vs. Negative Drainage?

Positive Drainage

Positive drainage is preferable for homes. It means that rainwater is being collected as it falls and then directed away from your home. During site preparation, it’s important to have proper grading of the soil. The land should slope away from your house at a specific grade depending on the type of surface.

Paved surfaces need a slope of at least one percent or at least one inch of drop for every 100 inches of horizontal travel. Turfed or landscaped surfaces need a steeper slope of two percent or a drop of two inches for every 100 inches of horizontal run. If the slope does not provide enough drainage, you could wind up with basement flooding, soil erosion, or damage to the foundation.

Negative Drainage

site preparationNegative drainage means water is flowing toward your house instead of away from it. This often occurs because your house is sited at the base of a hill or because the surrounding property is graded inadequately.

This can lead to pooling water, flooding, and cracks in your foundation. Installing a household gutter system can minimize the severity of the problem, but the only permanent solution is to find a way to redirect the water flowing downhill toward your home.

This may require removing landscaping and adjusting the grade. Another option may be to install a rain culvert or drainage ditch to collect the flow and channel it elsewhere. 


If you need help with construction site preparation to minimize future drainage issues around your home, contact Valley Excavating, a respected and experienced excavation company in Kalispell, MT. they have served the Flathead Valley for more than 20 years. In addition to site preparation, they also specialize in road construction and maintenance, land clearing, and septic installation. Learn more about the company at their website or call (406) 857-2086 to arrange a consultation.  

tracking