Building a deck is a wonderful way to add living space to your home. A deck will provide an outdoor area for friends and family to gather or to simply spend quiet time in your yard. This article is intended to provide suggestions to help you design and build your deck, every deck and its construction is different. These deck building instructions will describe a square deck that has one of its 4 sides attached to a house. The deck building techniques are common to most decks. Always consult with your local city or county building department to find out about any codes or regulations that would affect your deck building project. Often the Plans Examiner or Building Inspector will have recommendations that may help you build your deck. It is advisable to consult a structural engineer, especially for large decks or when the deck is carrying loads such as large amounts of people or hot tubs etc.
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Layout: Layout of the ledger is done by figuring out where it will be positioned on the wall and drawing an outline of it on the wall. Determine whether it is necessary to remove the siding from your house under the ledger and add flashing or if you can bolt the ledger directly to the siding.
Flashing: The connection point of the deck to the house is very vulnerable to water problems because the deck has the potential to hold water on top of it and if that water flows toward the house it needs to be kept outside. There are several precautions you need to take to keep the water outside. If done right you should have no problem. You will need two pieces of flashing: One to go over the top of the ledger and one to go behind the ledger and down and over the siding and or foundation below the ledger. If you are removing the existing siding be sure to install a “Z” flashing under the siding and over the top of the ledger to keep water from running behind the ledger. The place where you buy your lumber will help you find the size to fit your ledger.
Determine the distance below the floor level by adding together the following:
This is the top of your joist ledger. (usually 8 inches below the door threshold)
Mark The Ledger Location: Mark the elevation of the top of the ledger so you can easily see it. Determine the length of it and mark each end. Draw a line the full length of it with a chalk line or a level and a pencil.
Ledger Length: The end joists will go on the ends of the deck so the ledger will need to be shortened so the end joist can lap over the ledger. Cut your ledger to the length of your deck minus the thickness of the joist at each end, usually 3 inches if your joists are 1 1/2” thick, and attach it to the wall. The end joists are attached to the end of the ledger, the joists in between are attached using joist hangers.
tip: if the bottom of the deck joists are within a few inches of the top of the foundation make sure that the flashing coming from the back side of the ledger board goes over the face of the foundation so the water will run onto the face of the foundation and not behind it. This also helps with water drainage off the house.
Attach The Ledger: Attach the ledger with lag screws and washers. Make sure that the screws go into the vertical wall studs on the house. It is typical to use 2 screws every 16”. Place them about 2” from the top and bottom of the ledger. Drill holes in the ledger to make it easier to drive the screws. The screws should be long enough to penetrate the wall studs about 3”, so if your ledger is 1 1/2” and the siding 1/2” you will need to use 5” lag screws.
Layout the joist hanger locations on the ledger by putting a mark where each joist will go. Most decks have a joist layout of 16 inches on center but sometimes the joists can be laid out at 12 inches on center or 19.2 inches on center. Remember that the ledger is 1-1/2” shorter on each end to account for the joist that will be there so overhand your tape measure 1-1/2” when marking the layout. See our Layout page for detailed instructions.
Install the End Joists: Start at one of the ledger ends and install the first joist of the deck by nailing the end joist to the deck. The ledger was cut short on each end to accommodate the thickness of this first joist. After nailing the joist to the end of the ledger make sure the joist is level and eyeball its closeness to being square with the ledger as possible then nail a temporary board to the side of the joist to hold it, nail an angled board from the joist to the ground to keep the whole thing from falling over. The angled braces should be strong enough to resist movement when you bump into the deck. If you are in doubt, install another brace. Next install the other end joist at the opposite end of the ledger and brace it like you did the first end joist.
Install the Rim Joist and support and brace as needed: Now install the "rim" joist at the end of the deck. It will be 3 inches longer than the ledger because the rim joist overlaps ends of the end joists. Nail the rim joist to the two ends of the end joists that you already installed. It is a good idea to put a brace from the center of the rim joist to the ground.
Check the joists for “square” by cross measuring from corner to opposite corner, when the measurement is the same then your deck is square. (see drawing)
The easiest way to layout the footings for your deck, especially if you have angles on the deck or a sloping lot, is to build the outer perimeter of the deck first and locate the footings from the perimeter boards.
Layout The Beam Locations: Decks typically have a beam to hold all the joists above the ground. Every deck is different so check your plans to make sure the beam size and location are correct. Measure the proper distance from the house and mark the center of your beam on the end joists. This mark will be the center of your footing.
Layout The Footing And Concrete Pier Locations: Now that you know where the deck beam goes you can locate the footings that will hold the beam. Pull a string line between the two beam marks. Check your plans to see the exact location of the footing and post. Use a permanent marker to mark the string where the center of the footing and pier will go. Use a level or plumb bob to go from the mark on the string to the ground, this is the center of the footing and pier. Mark the center of the footing on the ground and then measure out from that to the edges of your footing hole. Now you are ready to dig the footing holes.
Layout The Stair Landing: The stair landing may be poured when the footings are poured so you may want to locate them now and form it so it is ready to pour when the concrete is mixed for the footings. Read the article How To Pour A Concrete Pad Or Landing to learn how to make a concrete pad.
The deck footings are the "feet" of the deck because a footing is what the deck stands on. Footings are made from concrete and poured in place.
Dig The Footing Holes: Dig a minimum of 12 inch round or 12 inch by 12 inch square hole for each deck footing. The holes must be deep enough so the bottom of the footing is below the frost line in your region. Digging the hole 6" deeper than the frost line and filling it with 6" of gravel before installing the concrete is recommended to give the footing better drainage, but may not be necessary if the soil in your area has good drainage. It is recommended to dig deep enough to allow for 6" of top soil on top of the footing to allow grass to grow.
This pier and footing installation method installs the pier and footing at the same time. You will install the cardboard concrete pier forming tube over the hole before the footing is poured. If you are not comfortable pouring the pier and footing all at once you can pour the footings first and after the concrete hardens you can come back and pour the pier.
Install The Pier Forms: After the hole is dug and gravel installed, hang a 8" or larger cardboard concrete forming tube in the footing hole. The bottom of the tube will be hanging above the bottom of the footing by 10 inches. To hold it off the ground use 2-2x6 boards and nail or screw through the board into the side of the tube (see drawing). The top of the tube should be six inches above the finished grade (grass, dirt or other material in your yard) and 10 inches above the bottom of the footing hole.
"Measure twice and build it once". Check everything again for square and proper heights before mixing the concrete.
Concrete can be purchased in 80 pound bags from a home store or pre-mixed by a local company and delivered by truck to your home. The easiest system to pour concrete when you build deck footings involves a truck that mixes the concrete on site. These trucks can mix only the amount you need so they are usually more cost effective for small projects like building deck footings.
Mix The Concrete: Mix the concrete so that it is thicker like oatmeal. Pour the footings first and let them set up for a few minutes and then fill the pier tubes to the top. If the concrete settles in the pier tube then the mixture has too much water, you may need to let it set up a bit and then top off the pier tube. You don't need to smooth the top of the footing but you will need to smooth the top of the posts as this will be visible when the cardboard is removed. Tap the sides of the tube to remove air holes where the cardboard meets the concrete. This may settle the concrete on the top of the tube, just add a little more to the top.
Amount Of Concrete Mix: Use the mixing instructions on the bag to determine the amount of mix to use for your hole size. A 12" x 12" wide by 12" deep hole requires 1 cubic foot. It takes about one and two thirds of 80 lb bags of concrete to make 1 cubic foot of concrete.
Post bases are metal connectors that hold the wood post holding the deck beam to the concrete pier or slab. The two types of anchoring include installing the anchor during the concrete pour or after the concrete hardens.
Post Base Install During The Pour: The simplest type of post base to use is one that has the 5/8" anchor bolt seperate from the post base. The anchor bolt is set in the concrete when the concrete is wet and then the post base is bolted onto the anchor bolt after the concrete hardens. The "adjustable" post bases have about 1 inch of play to allow a little bit of imperfect bolt placement. Use a string line pulled between the tops of the cardboard pier forming tubes to locate the anchor bolts when the concrete is wet. Make sure the bolt is no more than 3/4" above the top of the finished concrete.
Post Base Install After The Concrete Hardens: Installing the post base after the concrete hardens is done by drilling a hole in the concrete and anchoring the bolt in the hole with epoxy. (epoxy is sold where you purchase the post base).
Note: Simpson makes post bases designated AB for “Adjustable Base” which allow a lot of room for error, over 1 inch of play. If you are not comfortable with placing it by hand you may build a jig from a small piece of wood laid across the top of the tube. Drill a hole in it and install the bolt thru the hole, letting the bottom of the bolt hang down into the top of the tube. Either way make sure the top of the bolt is no more than 3/4" above the top of the finished level of the concrete. It is not recommended to drill in the anchor bolts after the concrete pier has hardened because drilling on a small surface area like a concrete pier may crack the concrete.
Bolt On The Post Base: After the concrete hardens attach the Post base on the 5/8" bolt. Make sure it is square with the beam direction and tighten the nut down.
After the concrete hardens and your post bases are set you are ready to cut the posts to the proper length.
Measure And Cut The Wood Posts: Move the string line that was used to mark the center of the beam to the edge of the beam and posts location, usually about 1 1/2". Do this at both ends so it remains parallel to the ledger on the house. Make sure the joists are still level and square with the ledger. Stand your post in the post base. Make sure it is plumb and just touching the string line. Mark the post where the string line hits it. Subtract the depth of the joist and the depth of the beam from the string mark on the post and cut the post to this length.
Install The Post Caps: Post caps are used to connect the top of the wood post to the wood beam. Use the fasteners that are recommended by the manufacturer. The joists should now be resting on the beam and not the temporary vertical braces. Keep the angled braces in place to prevent the deck from moving from side to side. Note, these are called lateral braces.
Mark The Beam: Layout the beam where the joists will rest on it. Make sure they match the ledger layout. Any time you build a deck you should always layout from the same side of the structure with the same spacing.
Mark The Rim Joist: Layout the joist locations on the rim joist for each joist.
Joist Hangers: Attach the joist hangers to the ledger on the layout marks. Make sure you do it on the correct side of the mark. When nailing a joist hanger on it is a good idea to use a piece of the joist that will be used to make sure that the hanger is set at the proper height and the opening is wide enough to fit the joist.
Angled Clips: Use angled clips to attach the joists to the beam, you can attach these to the beam before attaching the joist. Verify that you have the proper nail for your situation. A worker at the pro desk of your local hardware store can help you interpret the hanger catalog to pick the right nails.
Measure The Joist Length: Measure the distance between the rim joist and the ledger. Cut each joist to length and install it in its hanger and attach it to the beam.
Crown The Joists: Crown the joist by looking down the edge and putting the edge that bows up, up.
Set The Joists: Set the joists in their hangers on the ledger and on the mark or clips on the beam. Nail each one before moving to the next one. It is hard to nail on a joist when another one is next to it. Install blocking if it is required by local building codes. This is also hard to do after the decking is on. Nail the rim joist to the joists. Make sure that the rim joist does not bow out or in, you can pull a string line down the rim joist to verify that it is straight.
The most common, and strongest way, to build the deck railing is to attach the railing posts to the side of the joists. The posts will need to be attached before the decking material is installed. This step describes how to build a handrail on a deck. Read the article Deck Handrail Designs for ideas. Railings are required to be 42 inches high and have no more than a 4 inch sphere
Start At The Corners: Install a post at each corner of the deck. The post will pass thru the decking material and attach to the side of the joist. Attach the post using a
Some deck designs attach the railing posts to the top of the decking material but that is not as strong as running the post thru the decking and down the side of the joists.
Be sure to install blocking around the post at the level of the top of the joists so the decking can rest on it. Install the corner posts and stair posts first then evenly space the posts between. Verify the maximum distance between posts with local building codes.
Your are now ready to install the decking on your deck!
Start at the deck edge: Start by installing the first board at the outer edge of the deck and work towards the house. The decking boards always run perpendicular to the joist direction. Cut the deck boards so they land exactly on the center of a joist. You can let the ends of the decking hang over the edge of the deck and cut them all at once to make a nice straight line.
Spacing the joints: Spacing between boards is determined by the decking material. Man made products have different requirements than woods like pressure treated wood, hardwoods and redwood. If you are using a product that shrinks you can butt the edges up to each other if you are using a non shrink product you can put a 1/8” joint between the deck boards by using several nails in the joint when laying each board.
Finish at the house wall: Hold the board 1/8” off the wall to allow for drainage and air flow.
Fastening: Fastening the decking is best done with deck screws. Nails tend to work their way out of the wood and pose a tripping hazard. All screws and nails on the deck must be hot dipped galvanized, or stainless steel or aluminum. Use two screws per board on deck material up to 6” wide and 3 screws for wider deck boards. Decking screws have small heads that allow them to go under the surface of the deck wood to keep them out of harms way.
If your deck needs stairs you will want to read the article How To Build Deck Stairs. This article has detailed information on building stairs for your deck or other project.