The 100 year deck joist

The 100 year deck joist

In today’s world of deck building, everyone is talking about the top of the deck. Should your deck be pressure treated, cedar, composite material or some form of wood that is suppose to last you the lifetime that you own your home.

When building custom decks, gone are the days that you figure the deck will only last 15 years and you will have to tear it down and build a new one. Now if you are spending large amounts of money on the top of the deck then doing a few things to the actual structure of the deck will ensure that you never have to replace it.

First things first. You need to install proper footings to make sure that the deck never moves. The best way to ensure that the deck never shifts is to install FOOTING TUBES. A proper footing tube will come with a flared bell on the bottom, or sometimes called a big foot. A footing tube will start at the bottom at about 24 inches and taper to about 8 to 16 inches at the top. When these are placed a minimum of 4 feet in the ground the frost will never be able to get underneath them and heave the deck. Once they are backfilled and concrete is poured into them you can be certain that they will be there for a lifetime.

A couple of things you need to do before you build the frame of your deck on top of your footing tubes. You should lay filter cloth underneath the entire area where the deck will be constructed. This will ensure that you do not get weeds growing up under the deck. The more organics that you can keep away from the deck the less likely they are to rot. You need to weigh the filter cloth down so that the wind will not roll it up. Usually most people get a small load of gravel and have it placed over the filter cloth.

You will want to make sure that the framing of the deck will be at least 1 ft off the ground. This will allow airflow under the deck which will intern allow the deck joist to dry when they get wet.

If you are hanging the joist off beams or a ledger board, make sure that every joist gets a galvanized joist hanger bracket. You also should only use galvanized hanger nails to fasten the hanger to the joist. This will allow the joist to take a larger load without any movement at the ends.

For all your nailing you should only use galvanized nails and if you are using screws they should be either coated to reduce corrosion or be ceramic screws. This will help extend the life of the fasteners and help minimize repairs in the future.

Once you have placed the joist in the framing of the deck, before you install the top, there is one more thing that you need to do. Install a piece of waterproofing on the top of the joist. You want the waterproofing to be wide enough that it covers the top of the joist and wraps down the side of the joist. The waterproofing should only go about half way down the side of the joist. It should go half way down on both sides. This should be placed on every joist in the deck. The reason that you want to waterproof the top half only of the joist is because this will allow the joist to dry naturally. If you waterproof too much of the joist or all of it then any moisture that the joist does absorb will not be able to evaporate or drain out the bottom. The reason for the waterproofing on top of the joist is because all your fasteners will penetrate the top and on the upper sides. The waterproofing will coat the fasteners going in and stop the water from penetrating the joist. Also the space between the deck boards can be prone to holding water, because the air cannot dry that space.

Once you have the top of the deck on, you should install skirting around the deck from the joist down to the ground. You should use open lattice not closed lattice. This will do a number of things;

·         it will stop animals from making their home under the deck

·         it gives the deck a nice finished look

·         it will allow airflow under the deck to dry the joist.

So there you have what we call the 100 year joist. If you are having a custom deck built and you are planning to put a material on the top to last a life time then make sure that you ask your contractor about the 100 year joist.

Rob Abbott

Operations Manager

Village Builders Inc.