retaining wall drainage

Retaining wall drainage is critical. It ensures water does not collect behind the wall, causing it to fail. A quality drainage system collects and redirects rainwater away from the wall. It decreases pressure on the soil around the foundation and within the wall itself, reducing erosion and settlement.

Does my small retaining wall need drainage?

For smaller walls, weep holes are often only needed at the base, however larger walls need a grid-like structure with multiple small weep holes coming out of the wall. We recommend using a protective varnish over the wall to prevent the water from the weep holes creating stains over time.

Should a retaining wall have weep holes?

Weep holes allow water to escape from behind the wall. These holes should be regularly spaced in the horizontal direction. Retaining walls with a height greater than a few feet should also have weep holes that are regularly spaced in the vertical direction, forming a grid pattern.

Does a 2 foot retaining wall need drainage?

These walls need a drainage system regardless of the wall height. If there are poor draining soils such as clay behind the wall, there needs to be drainage incorporated the wall system. Clay when wet is very weak, so it is essential to provide a way for water to escape from behind the wall.

Do I need a French drain behind a retaining wall?

If you’re building a retaining wall, add a French drain behind the first course of stones or blocks. Otherwise, water moving down the hill will build up behind the wall and undermine it. The pipe should rest on the same compacted gravel base or concrete footing that supports the wall.

Can I drill drainage holes in retaining wall?

Install (or Add) Weep Holes

Every retaining wall should have them. And yes, you can add them retroactively — drill them into an existing concrete, stone or brick wall using a core drill and drill bit, which you can often rent at your local hardware or DIY home improvement center.

How do you divert water from a retaining wall?

To put drainage in a retaining wall, we recommend adding crushed stone or gravel behind your structure. Doing this will encourage water to exit from the drains or weep holes of your wall, rather than becoming stagnant behind it.

Does a 12 inch retaining wall need drainage?

Second, a retaining wall must have properly compacted backfill. Backfill refers to the dirt behind the wall. In order to provide proper drainage, at least 12 inches of granular backfill (gravel or a similar aggregate) should be installed directly behind the wall.

Why do you put AGI pipe behind retaining wall?

Behind the wall, a drain system must be placed to prevent water from pooling and undermining the structural integrity of the wall. The first step in this process is the placing of agi pipe covered with appropriate geotextile fabric and backfield around with suitable aggregate.

How deep should retaining wall footings be?

The general rule of thumb is to bury about one-eighth of the height of the wall. For example, if your wall will be three feet (36 inches) tall, the first course of blocks should start five inches below soil level. The gravel base should start three inches below this.

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