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HERE'S HOW- Install a Retaining Wall on Slope to Create Garden PDF Print E-mail
Written by Pat Logan, Creative Syndicate   
Thursday, 29 March 2012 02:04

Dear Pat: Part of my backyard slopes, so I want to install a retaining wall to level it for a garden. I have thought about using wood timbers, but blocks might look better. Which method is best? — Tina P.

Dear Tina: Both methods for building a retaining are effective and can be attractive depending on the landscaping appearance you are seeking. Retaining wall blocks create a more formal look, while using railroad ties or landscaping timbers appears more rustic.

It might seem as though stacking up landscaping timbers is the simplest do-it-yourself method to build a retaining wall, but it is the most difficult to do properly. I have seen many timber retaining walls rot away and collapse because they were not installed properly. It is not easy to replace the timbers later without disturbing the garden area.

If you want to build a curved retaining wall, then retaining wall blocks are the best method. Even if you do not need to have the wall curved, a slight curvature can be very attractive. An S-shaped retaining is particularly appealing because it provides a location on the lower level for an ornamental shrub or small tree.

The most difficult part of building a wall with blocks is just carrying them to your backyard. They are heavy but not unmanageable. Even if you use a wheelbarrow to make it easier, there is a lot of lifting. After moving them to the wall location, it would be wise to wait until the following day to start building the wall. It can be pretty hard on one's back.

Make sure you purchase special interlocking retaining wall blocks at your home-center store. These blocks fit together when stacked so they will not tip over from the weight of the soil behind them. There are various designs and degrees of offset (how far back each successive row is positioned), so take your time selecting them.

The key to installing a block retaining wall is preparing the ground for the first row. You should dig out a foundation area where the first blocks will rest. It should be about 1 inch deep for each 8 inches of wall height. Dig this area only as wide as the blocks and try not to disturb the nearby soil.

This foundation area should be level, so its depth may vary somewhat depending on the lay of the land. Once you have it dug out and leveled, tamp it down with a 4x4 beam or a hand tamper. It is important to have a solid base so it does not settle.

Once the base row is laid, let it settle for a day or two before completing the wall. When you find some that are not level, remove them and pour a little sand or fine gravel under them to bring them to level. Don't use loose soil you have dug out because it may wash away, and they will be out of level again.

Stack the successive rows of blocks until you have the wall to the desired height. Backfill each completed row with soil. Many block systems have a finishing cap to cover the final block, so this will add a little more overall height to the retaining wall.

Tools and materials required: shovel, spade, level, tamper, sand, gravel, blocks.

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