Basic Deck Building Instructions

These are basic instructions on deck building. Rather than overwhelm you with a fancy deck, let’s start with a basic square deck – say a 10ft X 12ft rectangle.

Below is a drawing showing the basic structure and terms for your deck. Click on the picture to enlarge.

Deck Terms

Knowing how the pieces fit together goes a long way towards understanding how everything works.

The first thing you want to do is determine is what you want the end result to look like. Visualize exactly how you want the end result to function. For example, where are the steps, doors, railing, etc.? Take some basic measurements to help determine the size of the final project.

With this information, you can now plan how everything will fit together. Let’s say that you are planning a rectangular deck 12 feet long, 10 feet wide and 24 inches above the ground. The outside of your home has vinyl siding or brick. There is no ledger board on the house and there are no water faucets or any other obstacles in the area you want the deck to go.

What direction do you want the deck building boards to run, parallel to the house or perpendicular? We need this information to determine what the structure will look like.

    • If you use a header joist to attach the joists to, you can place the posts at the outside edge and use them to support the railing or even a roof.
    • If you use girder beams in your deck building (as in the below drawing), the post will be under the deck and not as visible.

Both have advantages and disadvantages.

My personal preference is to have the post at the edge as this gives the most support to the railing.The drawing above is using girder beams and bolts through the header joist to support the railing posts.

Another preference I have is to have the deck NOT attached to the house. If you are not experienced, getting a ledger attached incorrectly can cause many problems later on. You simply cannot attach a board to the outside and not expect problems, even if you have a brick house. Water will find its way in.

Plan where the support post will be located and dig holes at least two feet deep. Remember the footer for your house will be close to the outside wall. Several inches away is OK as we can bridge the gap with the deck boards. By not attaching to the house during your deck building, you have greatly reduced any possible damage and intrusion by water and insects.

Dig holes where the support posts are needed and place the posts in concrete. There are two theories on using this method in deck building. Some say do not encase the posts in concrete. Place j bolts and use hangers. This way the wood will not rot. I use pressure treated 4×4 or 6×6 posts that will not rot. I have used them for a long time with no problems. Use your own preference. Line everything up and let the concrete set.

Attach the joist to the header joist using joist hangers if you are unable to get to the backside or use nails through the header joist into the end of the joist. If you are using 5/4 inch x 6 inch deck boards, the spacing of the joist should be 16 inches. If you are using synthetic decking and it is to be run at a 45 degree angle, the spacing should be 12 inches. A 24 inch spacing will always have “bounce”.

Another point during your deck building process, make sure every joist is the correct length so that any trimming will not be required when you attach the other end.

Attach the other end of the joist you attached at the house side to a header-joist board at the outside edge of the new deck. Everything should be level and square. At this point in your deck building process, you should have the basic frame in place and the post to hold the railings.

The picture to the left is a view taken from underneath the deck looking up.

We used pressure treated joists running away from the house. 2X6 inch beams will support the deck as we are only going out 10 feet.

If we had gone out 12 feet, you would use 2×8 inch pressure treated lumber. Your local big box or the internet can provide span charts to help ensure you use the correct size materials.

At this point in our deck building, it is the time to place the stair stringer for the steps. Most building codes require the run to be 10 inches and the rise to be a maximum of 8 ½ inches. Most of the precut stringers use 10 inch run x 6 ½ rise.

If you place the stringer and you have very narrow step, they are installed wrong. The stringers should be placed to allow a 36 in wide stair. Place stringers at each end and at least one in the middle or preferably two. The spacing will be 12 inches apart.

Nail from the backside into the stringer or use joist hangers to support the stringers. Support the bottom edge on concrete if possible. NEVER in the dirt.

After the stringers are in place, we are in the part of the deck building process when it’s time to place the steps.

Stringer Step One

The first one goes at the rear of the flat step with the edge touching the back.

Stringer Step Two

The second piece goes on top of this piece facing up. It should be even with the bottom edge of the step above.

Stringer Step Three

Now attach the front edge of the step. It should overhang the back piece by ½ inch. Do all the back bottom pieces, then the rear pieces, then the leading edge.

Now it is time to attach the deck boards to the floor joist. These run parallel to the house crossing the floor joist. Start at the outside and work toward the house. The boards should have an overhang of approximately ¾ inch. Place a gap between the boards of 1/8 to ¼ inch, depending upon how moist the boards are.

Before nailing them down look at the edge. The grain should run concave or down on the edges. If it turns up, the board will cup upward and hold water when it gets wet. Every board should have the edges facing down to help keep curling to a minimum. Nail every board at every joist the keep the boards flat.

If you did not cut all the decking before you started, it’s OK. Take a chalk line and mark and cut the ends square with a circular saw. Cut the deck boards to fit around the post and keep the project looking good.

At this point in the deck building process, all that is left is the railing. Trim the post to the desired height. Usually this is 35 inches or whatever your local code department requires. Cut pressure treated 2x4s to fit the inside dimensions between the post. Cut some 2×2 stringers into pieces 28 ½ inches long. Lay the 2×4’s on their edge on a flat surface of the deck. Mark the center.

Take a scrap piece of wood, typically 1 inch thick ( use two pieces of ½ inch plywood ), lay on the deck and lay the 2×2 pieces on them. This will space the balusters in the center of the railing. Nail the balusters starting from the center every 3 ½ inches apart toward the ends of the 2×4’s. Do this for every space between all the remaining post, except the stairs.

Take two pieces of 2×4 and place on the deck between the post. Set the pre-made railings on the 2×4’s. The top edge should be level with the top of the post. Toe nail the railings into the post.

The final piece is very easy. Take some long smooth deck boards and place on top of the post and the railings and nail into place. I like to offset the top piece so that there is 3/4 inch of overhang toward the inside of the deck. This leaves a lip on the outside of 1 ¼ inch. Use the same method for the stairs.

At this point in the deck building process, the deck is useable. To finish the deck building project, install some skirting around the bottom. I prefer plastic lattice as the color never fades, the weed eater will not destroy it and stuff can not get under the deck. Really makes the deck look great!

Below are pictures of the progression of our son Rob’s deck building project, which he built with the help of a couple of his friends. Click on each of the pictures to enlarge them.

Dave Altman

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