Deck – Installing a Ledger

A ledger is used when you are attaching a deck to your existing home. This board is bolted to the house, and the deck is hung on it. If a freestanding deck (not attached to the house) is being constructed, then you do not use a ledger. What you need is to add more bracing to stabilize the deck. One of the things to remember is that in some areas a deck attached to a house will be taxed, but if it is separated by even an inch or two it will not.

The Level of the Ledger

First of all, you will understand that the level of the deck will be at least 1-3″ below the level of the finished floor inside the house. No one wants to trip over the deck when stepping out of the house and it also would not make sense to install a deck higher than the floor inside a house, as water runs in if it rains.

The top of the ledger then will be 1 1/2″ below the final top surface of the deck because that is the thickness of the decking board (1 1/2″) that will be nailed on top. For example:

  • Leave 1″ – 3″ drop from your door
  • Allow for the size of your decking boards – that will be another 1 1/2″
  • So measure 2 1/2″ – 4 1/2″ down from your indoor floor level
  • Mark the wall showing the highest point of the ledger

        If the deck joists, which support the decking or surface of the deck, are installed on top of the ledger (rather than hang from it) then the top of the ledger will be lower than the final level of the deck. Decide whether you want to hang the joists from the ledger or rest them on top before you start your installation work.

        Location on the Wall

        Make sure that you secure the ledger properly. Position the ledger at a point on the wall where, once it is attached, the lag screws attaching the ledger will penetrate something solid such as wall studs or floor joists. Placing ledgers at the same level as the floor joists of the first floor solves the problem as the lag screws will penetrate the band joists. If you’re positioning the ledger else where, and if there’s nothing solid to have the lag screws attached to, then you will need to attach the ledge with bolts.

        Tip: For areas that see a lot of heavy rain or snow, a metal flashing on top of each deck board will be needed, as this helps keep water from getting trapped between the decking and the joists, thus causing rot.

        Choosing the Ledger

        Choose vertical grain board as this kind of wood comes from the center of the tree and will show center circles. This is ideal as deck building ledgers should be free of ingrown knots and flaws (or at least only have very small knots). Those with arc grain are prone to warp and cup over time. Be sure the board, as with all decking materials, is of redwood, cedar, cypress, or pressure-treated lumber.

        Once you’ve decided on the materials for your ledger and other building material, check the foundation of the work area to see if there are any obstructions, such as hose faucets, dryer vents, gas or water pipes, electrical wires and so forth. These obstructions have to be relocated. Anything that is below the ledger will be underneath the deck and therefore less accessible to repair.

        The services of an electrician or a plumber will be needed to rearrange some wires or pipes if you cannot do this yourself.

        Locate and mark any underground pipes or wires before you begin digging the foundation holes so that you will not be disturbing them.

        Tip: Because you will be exposing the structure through lag screw holes, use some silicone caulk in the holes before you screw the lag screws in. This is to help keep rain water running down the wall from flowing into the structure.

        Installing the Ledger

        1. The ledger is usually the same size as the joists. Cut it to length, which is the total length of the deck minus 3” (for 2 x 1 1/2’’ thickness of joist on each side).

        2. With the ledger resting on saw horses, mark the lag screw locations. These should be in pairs, one on top of the other, every 30”, or staggered singly every 15”, making sure each hole is at least 1” more from the edge of the board for proper holding.

        3. Drill the holes with a bit that is 1/8″ larger than the actual screws so that you will have a little play for adjustments.

            Positioning of ledger

            4. Mark the corresponding holes on the siding, and drill the holes in the siding.
            5. Nail one end of the ledger (the top part) temporarily in place. Then get it exactly level with a 4’ – 8’ level on the board, and temporarily nail in the other end. Check once again to be sure it is exactly level before marking the holes. Mark the lag screw holes that were drilled in the ledger on the wail with a felt tipped pen. Remove the ledger.
            6. Drill the lag screw holes in the wall. REMEMBER: Use a bit that is one size smaller than the shank of the lag screw to ensure that the lag screw has a good bite into the wall. Drill straight into all the holes, making sure that you are drilling into solid wood, or use the blocking and bolt method described earlier.
            7. Squirt some silicone caulk in the holes in the wail before screwing in the lag screws to keep rainwater running down the wall from flowing into the structure through the lag screw holes.
            8. Precaution – Before you attach the ledger permanently: If the ledger were attached directly against the wall, with its back surface against the wall, trapped rainwater running down the wall can cause rotting. Leave a small space (1/2”- 3/4”), so that water can continue to run to the ground. This can be done with washers on the lag screws between the ledger and the wall which have been hot dipped galvanized (HDG), which do not rust. Use aluminum washers if your wall is aluminum siding.
            9. Thread the lag screws into the ledger, then install the proper number of washers on each screw. If the siding is not flat but has different surface levels (beveled siding, aluminum siding, shingles, etc.), compensate with more or fewer washers on the top screws than on the lower ones so that the ledger is installed true vertical.
            10. Squirt caulk into the holes, lift the ledger into place, tap the screws into the wall. Tighten the screws and make sure they are biting solidly into the wall, especially the last 2”.
            11. You are now ready to install the two edge joists and locate your pier holes.

            Paint waterproofing on the cut ends of the ledger and all other exposed boards, especially if you are using pressure-treated lumber or a decay resistant lumber that is not all heart.