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Providing Drainage for Retaining Walls

Project Overview

Providing Drainage for Retaining Walls

The life span of a retaining wall depends largely on its drainage. Dry soil places very little stress on a wall, but wet, heavy soil causes the wall to buckle or lean, and means extensive repairs can't be far behind. No drainage system can handle a flood, but a good drainage system will prevent most water damage. The biggest trick-short of the excavation- is finding a place for the water to go. Bring the drainage pipe around the wall and continue running it until it comes to the surface.

4 Steps

  1. DIG A TRENCH
  2. COVER WITH LANDSCAPE FABRIC
  3. LAY THE FIRST COURSES OF THE WALL AND THEN ADD A GRAVEL BED
  4. LAY GRAVEL IN THE TRENCH
DIG A TRENCH
DIG A TRENCH

Step 1

DIG A TRENCH

Lay out the wall with batterboards and level lines, and dig into the hill to create a level trench as deep as is required by the wall you're building. Place some of the excavated soil on the slope's low side to help flatten the area. Make sure the trench is a uniform depth (and level) by taking measurements at various points along a level mason's line. If the measurements vary, add dirt (and tamp it) or remove dirt where necessary.

COVER WITH LANDSCAPE FABRIC

Step 2

COVER WITH LANDSCAPE FABRIC

Landscape fabric prevents the soil from clogging your drainage system. Unroll enough fabric to run along the length of the trench twice, plus an amount a little more than the depth of the excavation. Pull the fabric across the back and bottom of the trench.

LAY THE FIRST COURSES OF THE  WALL AND THEN ADD A GRAVEL BED
LAY THE FIRST COURSES OF THE  WALL AND THEN ADD A GRAVEL BED

Step 3

LAY THE FIRST COURSES OF THE WALL AND THEN ADD A GRAVEL BED

Leave space at one end for the drainpipe to exit through the wall. Behind the wall, lay a gravel bed that slopes 1 inch every 4 feet as it travels across the hill. Check the slope with a 4-foot level sitting on a straight 2x4 with a 1 -inch spacer under one end. Add or remove gravel to get a level reading. Lay drainpipe along the back of the wall. It, too, should slope 1 inch every 4 feet. Continue the pipe around a sidewall, if any, without kinking the pipe. Continue to run the pipe downhill until it reaches the surface.

LAY GRAVEL IN THE TRENCH
LAY GRAVEL IN THE TRENCH

Step 4

LAY GRAVEL IN THE TRENCH

Cover the drainpipe with gravel as you build the wall. Lay the first few courses and fill in behind them with gravel. Tamp the gravel firmly. Continue to build the wall, filling in with 4-inch layers of gravel and tamping as you go. Lay gravel behind the wall until it is about 6 inches from the top. Pack down the gravel with a tamper, then fold the landscape fabric over the gravel. Fill the remaining space with soil and tamp it in place. Fill any low spots that result, then rake the area level. Sod, seed, or plant with the groundcover of your choice.

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Project Details

Skill Level: Intermediate

Time: 2 hours

Before you start, read this »

Due to differing conditions, tools, and individual skills, The Home Depot® assumes no responsibility for any damages, injuries suffered, or losses incurred as a result of attempting to replicate any of the home improvement ideas portrayed in this website Before beginning any home improvement project, review it thoroughly to ensure you or your contractor can finish the project and if any doubts or questions remain, consult local experts or authorities. Because codes and regulations vary greatly, you always should check with authorities to ensure that your project complies with all applicable local codes and regulations. Always read and observe all of the safety precautions provided by any tool or equipment manufacturer, and follow all accepted safety procedures.

Materials

  • Perforated plastic drainpipe

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