Gutter crew pointed the downspouts uphill on a steep lot. Will the water come back to the foundation?

The Department of Energy's Building America Solution Center, drawing on EPA Indoor airPLUS specifications, says downspouts should end no closer than 5 feet to the foundation, on grade that slopes off, or feed an underground catchment 10 feet or more out that is not tied to the foundation drain. It singles out the outlet: a daylight drain has to empty onto ground that carries water off and keeps it from running back toward the house. Roof water released uphill of a house does the reverse. It flows back down the slope to the wall the gutters were hung to protect.

Soil raises the stakes. The Solution Center says gutters and downspouts matter most where soils are expansive or collapsible. Expansive soils swell when wet and can push on a foundation hard enough to crack it, while collapsible soils settle and can form a trough that holds water against the wall.

The grading guidance assumes ground that falls away from the house, at least half an inch per foot for 10 feet under ENERGY STAR rules cited by the Solution Center. Where walls, slopes or other barriers make that impossible, the program calls for swales or perimeter drains that lead the water off and around the house. On a lot like this one, that points to two pieces of work: a swale uphill of the house to turn the hillside's own runoff around it, and downspouts piped around the side of the house to an outlet lower than the foundation.

For that piping, the Solution Center specifies non-perforated ABS or Schedule 40 PVC pitched at least 5/8 inch per foot downhill from the house. It warns against connecting gutter drains to the perforated foundation drain, which soaks the footing the system is meant to keep dry.