Build a Solid Retaining Wall: Phase 2 The second of two parts

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By Mark Clement Having planks delivered well ahead of time helps ensure they'll be as dry as possible by installation. Planking The first step to getting a planking job that'll last is to order your materials way in advance and have them delivered. Some suppliers' pressure-treated stock has a lot higher moisture content than others. The drier the stock is when it goes in, the smaller the gaps will be in the vertical wall planking as it dries out. The caps will also fare better and joints stay tighter if the stock is dry. Screws serve as cleats for installing the planking. Installation. To make sure I'm not left with a gap between the top course of the 2x8 planking and the 2x10 wall cap, I install the planking from the top down. This ensures as solid a wall surface as possible. And I make sure to set the bottom plank no less than 4 inches below grade to keep material from seeping out the bottom of the wall. Using long bar clamps to hold the planking tight to the previous course makes this process far less painful than it might sound. While gun nails work to hold planking solid, a layer of DAP deck adhesive between the posts and planks adds a nice insurance policy and gives the wall another layer of protection from racking, especially in shifting soils. Once the planking is in, I drill 1-1/2- inch diameter weep holes in the center of every bay on the bottom plank course. Using landscape fabric behind the wall keeps dirt from filtering between the planks. Next, on the inside of the wall planking, I apply a sheet of geotextile fabric with a hammer-tacker to keep mud and silt from leaking through the planks. Be careful not to rip it as you install it; lap any joints by no less than 4 inches in a weatherboard fashion. Backfill At the base of the wall, I lay out another roll of geotextile fabric and cover it with at least a foot of 2-inch trap rock or rubble (this is a great place to get rid of rocks and rubble from the site). Then I wrap the rock with more fabric so water can flow in the voids between them. Now it's time to backfill the hole. If the wall is particularly long, this might be a good time to rent another skid-steer or pull in some strong backs. You'll probably need more backfill than you dug out, so be prepared with fill from around the site or to have some brought in. The cap adds the finishing touch. A butt joint at the corner is less likely to separate than a miter joint. Cap The final piece of the wall is a 2x10 cap. My wall has four returns, and I wanted those corners to look nice, but a miter joint in treated lumber is going to open. Instead, I routed a round-over around all my cap planks with a trim router and butt joined them at the corners. I used 3-inch deck screws to fasten the cap for a nice clean look that'll last. For a splash of color, you can use Western red cedar for the rail cap as long as it's not in contact with the ground (some ugly ground-dwelling bugs like to munch on cedar). The last earthwork step is to add another loose layer of backfill an inch or so away from the bottom of the cap. The loose fill is suitable for plantings and grass. Now is the time for the landscaper, too. You can trick out all the niches in this wall system with plantings or lights or just grow grass. I used a couple of bags of Scotts Patchmaster grass seed to fill in the lawn on my project. When the homeowner watered it twice a day (morning and night), thick grass popped up in about a week. It was better than any straight grass seed mix I've ever used. However you treat the wall with plants, you've got a feature to be highlighted--and not something the landscaper needs to creatively hide. Mark Clement is a remodeler and author of The Carpenter's Notebook and The Kid's Carpenter's Workbook, Fun Family Projects! Find out more at www.TheCarpentersNotebook.com. PREVIOUS  1 | 2 RELATED ARTICLES: Build a Solid Retaining Wall: Phase 1