I have spent two days searching the web but haven't found out how to define the following parameters for weep holes in retaining walls.

  1. horizontal and vertical (if staggered situation) spacing between each weep hole;
  2. slope degree;
  3. diameter;
  4. the space between bottom of the ground and the weep hole also form the top as well.
  • $\begingroup$ I've typically not seem the weeps defined to that level. I've defined them as a X" pipe to provide positive drainage to the exterior of the retaining wall at an interval of Y' maximum. If more specification is needed I would typically see it drawn into the plans and elevations of the retaining wall. $\endgroup$ Oct 10, 2016 at 19:32

1 Answer 1


retaining walls are usually under 10-foot high if they are designed based on gravity with regular toe and heel foundation. These walls are treated on the backside with a waterproofing chemical or a plastic membrane which is backfilled with gravel to let the water run down to a 4-inch diameter PVC pipe perforated on top every 6-inches installed with a slope of 2% to 3% on the bottom of the wall draining out into storm drain system. There is weep holes as a back up every 4-feet by either 1-inch PVC or ornate cast iron pipes.
Retaining wall shorter than 8-feet are usually made by concrete blocks and the same general detail of drainage applies to them except the weep holes are created by leaving every 4th joint on the first row ungrouted.

Taller retaining walls or the new thin retaining walls anchored by horizontal epoxy coated tension cables (nails) have elaborate drainage systems engineered by the geotechnical soils engineer as an integral part of the backfill drainage network.


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