Often the most difficult part of building a deck is attaching the deck to the house. Most homes have a poured concrete foundation making it tricky to attach the ledger board. The ledger board is the board that will take the weight of the deck frame and decking. Attaching it to a poured concrete wall is not difficult but does require some special tools and materials. The best way to anchor a board to concrete is with "sleeve" anchors. Sleeve anchors have a metal sleeve around a bolt. As the bolt is tightened the sleeve expands and presses against the concrete creating a very strong anchor that does not stress the concrete.
Measure and mark the location for the ledger board against the concrete wall. Then mark the wood indicating where the joists will go, usually every 16 inches. The concrete anchors should be placed where they will not interfere with the placement of joists. At the first and last gap between joists and in every other gap in between make a mark for a sleeve anchor. For each anchor mark, drill a hole the same size as the anchor sleeve.
Prop up the board against the wall making sure that the board is aligned with the location marks on the wall. Mark the anchor holes on the concrete using a carpenter's pencil. Take the board down.
Drill each hole in the concrete using a heavy duty power drill and a masonry bit. The size of the bit should be the same as the diameter of the sleeve of the anchor. Make sure that you keep the drill perpendicular to the surface of the wall so that the anchors will go straight in. If the anchor goes in at an angle it may not line up with the holes in the ledger board. The depth of each hole should be ½ to 1 inch deeper than the minimum embedment length of the anchor (marked on the anchor itself). A piece of tape can be put on the drill bit to indicate the correct depth.
Clear any debris from the inside of each hole. Place an anchor through the ledger board and into the concrete hole at each end. Set the nut on the anchor flush with the top of the bolt and tap the anchors in with a hammer. Setting the nut this way prevents damage to the threads. Push the board against the concrete and tighten the nut by hand. Once the ends are in place it should be easy to insert the remaining anchors. Tighten the anchors gradually, making sure that the wood is flush against the concrete.
Install the flashing to protect against water damage. Once the ledger is attached to the wall aluminum flashing needs to be installed. This flashing can be found pre-formed (typically called a "drip cap") or can be made from plain 1/16 inch aluminum sheeting 12 inches wide. Attach the sheeting so that the bottom edge of the aluminum is two inches from the top edge of the ledger. Anchor the sheeting with waterproof (stainless steel) pan-head wood screws every foot or so. Press the sheeting into the corner where the ledger board touches the wall so that the sheet makes a fold. Using silicone caulk, caulk the edge of the flashing that touches the concrete, creating a waterproof barrier.
Things You Will Need
- Heavy duty power drill or hammer drill
- Carbide tipped masonry bits
- ½-inch diameter concrete sleeve anchors
- Pressure treated wood ledger board
- Aluminum flashing
- Silicone caulk
- Using a hammer drill will make the drilling go much faster and make it less likely for the drill to overheat.
- To keep the drill from overheating, drill into the concrete a little bit and then pull the drill out. This will clear debris from the hole and make it easier to drill.
- A can of compressed air works very well to clear out dust and dirt from the holes in the concrete.
- Even a heavy duty drill can overheat and burn out if worked too hard. If the drill starts to feel hot or gives off a burning smell, let the tool rest and cool off.
- Always wear eye protection when using power tools.