Ground surface treatment

The ground at the top of the foundation wall offers the first line of defense against a wet interior space below. The more water that can be removed from the equation at the earliest opportunity, the better the total waterproofing or dampproofing system will function. This area is sometimes neglected but is crucial to success in both dampproofing and waterproofing.

A few simple procedures at the surface level are:

Old House Web
Old House Web

  • Keep the water that comes off the roof from ending up in the basement by using a thorough gutter system. Collect the water in gutters and send it well away (10 feet at least) from the foundation wall in downspouts. Don't undersize either component—the smallest sizes clog easier and overflow quicker.

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    This downspout discharges too close to the foundation.

  • Compact backfill in lifts next to foundation walls, otherwise it will settle over time and form a reverse slope, putting water where it's unwanted. However, be careful not to crush the drain pipe in the initial lift.

  • Final grading should form positive drainage away from the house. The IRC requires a ½ inch per foot slope for at least 6 feet. Maintain this everywhere, through foundation steps and around corners.

  • Some designs call for the use of downspouts discharging into 6-mil plastic pipes 6 inches below grade with the same positive slope to prevent excess surface water from percolating down. This is especially true in cold climates where heavy ice and snow on the roof preclude the use of gutter systems.

  • Even properly graded and compacted surfaces can change over time, so the ground around the house may occasionally need to be re-dressed to account for settlement of the backfill.

  • Trees, according to the Department of Housing and Urban Development, should be no closer to a foundation than their eventual height, otherwise tree roots can clog drains and can dry out soils enough to cause settlement.

  • In areas where expansive soils are present, it is doubly important for structural reasons to prevent water from infiltrating under footings or slabs.

While there may be resistance to spending time and money on something a homeowner may never even see or think about again, it's best to do it correctly from the start. It's been said before, but it's never been more true than in this area of residential construction—it's much easier and cheaper to do it right the first time than to dig it up and fix it later.

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