How To – Installing A Ledger For Your Deck Or Porch

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    Probably the most important part of your deck or porch addition is how it is fastened to your home.

    With so many different design options for your addition there is really only one way to attach the most important structural part of your deck and that is by using a ledger board and carriage bolts as fasteners.

    Some contractors will have you believe that you can simply nail or lag bolt or build a free standing deck but all of these options will result in structural failure. The Home Builders Association along with National Code Agencies all agree that the most common reason for injury is the improper use of fasteners.

    Nails even if they are hot dipped galvanized will corrode and work their way lose over time. The same is true for Lag Bolts which are nothing more then large screws. Free standing decks and additions can be built to withstand movement and failure but this means expensive cross-bracing and larger then normal posts which can accept notching.

    Since most Home Owners will never get under their decks and porches to inspect the fasteners this needs to be done while the work is being performed. If you are buying a home with a deck or porch you need to make sure your inspector verifies the proper use of Carriage Bolts and Joist Hangers.

    With this said lets move on to our deck project and take a look at how you can install your ledger board correctly.

    The first thing we need to do is remove the siding from our home. Many contractors will just attach a deck through the vinyl or wood siding and not prepare the attachment points correctly or add additional water barriers.

    Here you can see we have removed about 2 feet of siding and are preparing to install our water resisting membrane under our tyvek house wrap.

    It is important to keep the house wrap in place over the membrane because it will shed water moisture down the inside of the siding and on to the ground. Not replacing it could cause failure later.

    A large section of membrane is placed against the wall and secured with just enough nails at the top to hold it in place. When we replace the top piece of siding that will line up with the surface of our deck those nails will help secure the membrane and the ledger board will be tightly fastened to the wall securing the bottom.

    After the membrane is installed we can insert  a few nails between our homes sill plate 2×4 and the top of the foundation.

    These nails will act as a temporary support while we attach the ledger board to the house.

    This is a great trick if you are doing the job alone. A long 3 1/2″ common nail will be able to hold the board as you check its level and attach it to your house with a couple temporary nails.

    Once we have checked the level of our ledger board and attached it with temporary nails we can then begin drilling holes for our carriage bolts.

    Drill each hole slightly undersized. you want to have the hole small enough that you need to force the bolt into the hole with a hammer.

    Remember over the next few months your Pressure Treated Lumber will lose moisture and you do not want elongated or larger then necessary holes to cause you problems.

    Fill the holes with an exterior grade siliconized window and door caulk.

    The longer rated the better and you should see an exterior rating of about 15 years.

    Once the hole is filled pretty good you want to coat the threads and head with caulk.

    Although pushing the bolts through the holes will probably get them pretty coated with caulk.

    Try not to coat the last few threads with caulk because you will need to install nuts and washers later on the inside of your crawlspace or basement.


    Once you have all the Carriage Bolts in place you can go inside and start fastening them with nuts and washers. You should use a large flat washer against the wood and then a lock washer followed by a nut.

    You will want to recheck all the bolts in about 2 months after the deck wood has had time to shrink. More then likely you will need to re-tighten them.

    Once you have the Ledger bolted to your rim-joist you need to protect it with Z-Flashing.

    Zflashing can be purchased already bent and comes in brown or white as standard.

    The main function of Z-Flashing is to stop water from getting between your ledger board and your home and rusting out your carriage bolts.

    ZFlashing is another step that most contractors will leave out so make sure that they spend the extra $10 and install it all around your ledger if you are not doing the work yourself.

    The first thing you need to do is apply a good bead of caulk to the top of the Ledger.

    Lay the zflashing on the ledger and fasten the top corner. 

    Nailing should be minimal and if you need to nail through the flat area you should cover the head with caulk.

    Once the zflashing is in place you can install your joists and decking.

    Your final piece of siding will be placed back on the house much later just before you install your deck railing.

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