Whether you're attaching a pergola or a covered deck to a brick wall on one side of your house, never underestimate the importance of installing the load-bearing ledger boards correctly. Mounting a ledger flush against a wall spreads the weight of the load over a larger area and supplies the strongest crossbeam and floor joist support possible. Also, unless the joint between the two surfaces is waterproof, moisture can infiltrate between the rough brick and adjacent wood, causing the inside face of the ledger to rot and decreasing its effectiveness to do its job.
Place your ledger board flat side up on top of a pair of trestles. Use a steel measuring tape, carpenter's square and pencil to mark lines on the board indicating the placement of supporting lag bolts; space the bolts 35 to 40 cm (14 to 16 inches) apart. Draw a small line across each mark 3.8 cm (1 1/2 inches) from both top and bottom edges of the ledger to mark the centres of the lag bolts.
Drill 6 mm (1/4 inch) pilot holes through each mark with a drill. Hold the drill at a right angle to the board and drill straight through the board by applying moderate pressure.
Measure vertically up one side of the wall and mark the position of the top edge of the ledger with a light-coloured grease pencil. Draw a horizontal guideline across the wall to mark the placement of the ledger with the aid of a long spirit level.
Hold the ledger against the wall with its top edge lined up with the guideline. Have helpers to support either end of the board. Place the spirit level on top of the ledger and centre the bubble once again to ensure it the ledger is perfectly level. Drill two 6 mm (1/4 inch) pilot holes through the upper pilot holes on each end of the ledger and into the brick behind with a masonry drill bit. Lay the ledger to one side.
Enlarge the two end supporting holes by drilling into them again with a masonry drill bit the same diameter as your lag bolt anchors. Drill out the upper end pilot holes in the ledger with a plain drill bit 2 mm (5/64 inch) bigger than your lag bolts; this allows sufficient clearance to help you level the ledger as you bolt it down.
Drive lag bolt anchors into the two supporting holes with a hammer, ensuring their edges are flush with the brick surface. Have your helpers lift the board into place and attach the ledger temporarily to the wall with a lag bolt at each end. Place a washer over each lag bolt before threading it into the anchor. Loosely secure the supporting lag bolts with a socket wrench, but don't tighten all the way.
Place the spirit level on the top of the ledger and centre the bubble by tapping the end of the ledger up or down with a hammer. When the ledger is perfectly level, tighten the two supporting lag bolts firmly with a socket set.
Drill the remaining pilot holes through the ledger and into the wall with a 6 mm (1/4 inch) masonry drill bit. Unbolt the ledger from the wall and widen all the pilot holes carefully as you did in step 5. Hold the drill at a 90-degree angle to the wall while drilling. Drive the rest of the lag bolt anchors into the wall and hammer them flush with the surface.
Counter-bore all the holes in the ledger to the depth of the head of the lag bolts, using a drill the same diameter as the lag bolt washers; this countersinks the lag bolts level with the surface. Enlarge the rest of the lag bolt pilot holes in the ledger with a drill bit 3 mm (1/8 inch) larger that the lag bolts.
Lift the ledger back into place and attach it to the wall with the two upper supporting lag bolts on each end. Place the spirit level on top and level the ledger again. Once the ledger is perfectly level, tighten the two supporting lag bolts firmly at each end, insert the rest of the lag bolts across the ledger, and tighten them all securely with the socket set.
Cut a length of galvanised stepped continuous ledger flashing to the length of the ledger with a pair of tin snips. Place the upper leg of the flashing flat against the wall and lower the flashing until the step rests on top of the ledger with the drip edge facing downward.
Attach the flashing to the brick wall with masonry nails hammered in and spaced every 30 cm (12 inches) across the length of the flashing.
Load a caulking gun with outdoor-grade silicone caulking compound. Run a horizontal bead of sealant across the wall, overlapping the top and side edges of the flashing and the brick surface. Dip your finger into water and run its dampened tip across the silicone bead to press the silicone firmly into the joint. Complete the seal by running a second bead across the joint and smoothing it down lightly against the first layer of silicone.
Seal the heads of all masonry flashing nails and lag bolts across the wall by applying a penny-sized dab of silicone sealant to their heads and smoothing the surface down with the tip of your dampened finger.
Log onto a reputable building web site and run load-bearing calculations to ensure that your ledger is the correct size for your job. Use a ledger made out of high-grade cedar or redwood if your budget allows the added expense; otherwise, use pressure-treated lumber. Make sure your ledger isn't bowed or warped. Use stainless steel or colour-plated lag bolts and washers throughout the installation to prevent corrosion.
Obtain necessary building permits by having your plans approved by the county planning department before buying any building materials. Wear a hard hat, safety goggles and workman's gloves during the installation.