A Guide Before You Build a Deck

Building your own deck is a tempting DIY project that many people complete successfully, and others regret ever attempting. Entire books have been written on the subject, and it’s not something that should be attempted if you’re unsure of your basic carpentry skills. This article will give you an overview of the process, focusing on the basic principles of construction, but detailed plans and other information that’s required for actual construction. 


Codes, Permits, and Planning 

Before even contemplating a deck, check with your local building authorities to determine if there are any restrictions and if building permits are required. Many communities have set-back rules that determine how close you can build to property lines, as well as requirements for heights, structural supports, and dimensions for railings and stairways. Your building inspection office really should be the first place you go, as they can tell you much about how you should build, whether you can build, and variations in deck construction—all of which will tell you if you want to build at all. Did you know, for example, that decks must be supported by footings that reach below the winter frost line in your region? This will mean you might have to dig holes and pour fittings that are four feet deep or even more if you live in a cold region. 

Be aware that building a deck -any deck–will have you doing a fair amount of problem-solving. The more carefully you consider all your options and possibilities up front, the smoother your work will go. For example, will your deck be anchored to your house–a construction style that requires that you remove siding–or might it be possible to make your deck freestanding to avoid this complication? This and many other possibilities should be considered up front to make for a smooth project.

Do your homework. Obtain a good blueprint plan for your deck or read a couple of good books on the subject. Make hand sketches of the deck you plan to build and walk through the steps mentally before starting — the more time spent visualizing the work that’s about to come, the better. 


Tools and Materials, You Will Need 

Deck building is a full-featured construction project, and you may need to buy or borrow quite a few tools if you don’t already own them. And the list of materials is impressive as well. Be aware that even a simple deck can cost you several thousand dollars in lumber, hardware and possibly new tools. 

Here are typical tools required to build a deck: 

      • Circular saw
      • Table saw
      • Power mitre saw
      • Shovel and post-hole digger
      • Cement mixer or wheelbarrow
      • Carpenter’s level
      • Carpenter’s square
      • Caulk gun
      • Drill and bits
      • Wrenches
      • Hammer
      • Tape measure
      • Eye protection
      • Particle respiration mask
      • As for materials, you may need: 
      • Metal flashing
      • Caulk
      • Pre-mixed concrete mix
      • Gravel or crushed stone
      • Cinder blocks 
      • Post caps
      • Post bases
      • Seismic ties
      • Joist hangers
      • Cardboard tube concrete forms
      • Metal Rebar
      • HDG bolts or lag screws, and washers
      • Joist hanger nails
      • Deck screws or stainless steel or HDG nails

As regards the lumber, there are too many variables involved to give precise dimensions or quantities. Suffice it to say you will need a lot of it, and in a lot of different dimensions, including 6 x 6 or 4 x 4 posts, 2 x 10 or 2 x 12s for joists and beams, 2 x 4s for other structural members, and 1x dimension timber or decking boards for the surface of your deck. Again, your local residential building codes will dictate the size of lumber you will need for the various structural components of your deck.


While interior carpentry projects can be framed with ordinary pine lumber, outdoor projects like a deck require lumber suited for exposure to moisture. This means that you will use wood species like cedar or redwood for some key components, and pressure-treated pine for many of the key structural members. 


Basic Construction Variation 

Decks that rest smack up against a house are usually anchored to the house with bolts (or lag screws). This must be done by attachment to solid wood, usually the rim joist or studs underlying the house siding. For the non-carpenter, removing your house’s siding is a pretty scary proposition. There is, however, an alternative method: the freestanding deck. Freestanding decks are a bit more work because the house-end of the freestanding deck will have to rest on additional post footings rather than being connected to the house. That means extra digging for you and additional concrete work. But for the sake of your peace of mind, this alternative may be worth the extra work. Another advantage is that in some communities, a structure that is not directly attached to the house does NOT need a building permit for construction. 


In the general overview that follows, though, we’ll describe a deck that is being anchored to the house structure itself.


Stage 1: Preparing the Site 

Assuming you have found or created your deck design plans and assembled the necessary tools and supplies, the first stage of actual physical work will come in preparing the site. 


Using stakes and string, outline the shape of the deck on the building site. If your deck is a simple square or rectangle, measure diagonally from corner to corner, both ways; a square layout will have diagonals with the same measurements. 


Using a shovel, remove any grass or weeds from this measured area to form your working space. Later, before closing off this working space with decking, you can apply mulch over this space to suppress weeds. But for now, your main concern is to furnish yourself with as level a working space as possible. This will be important later in the project when you dig holes for footings or concrete piers that will need to be installed perfectly level. 

Carefully mark out where the ledger board will attach to your house. This ledger will support and anchor the side of the deck that is adjacent to the house. The level at which the top of the header board rests should be the same as the level of your joists, which will form the framework upon which the surface decking will lie. It is critical to ensure that the header is not only at the proper height but also that it is level. Consult your deck plans when outlining the position of the ledger board on the house.

Now mark out the location for the footing posts on the building site. How many supports you will need, and how deep footings will need to be, are dictated both by your building plans and the requirements of your building inspection office. 


Stage 2: Install the Ledger 

The ledger board, usually a 2 x 10 or 2 x 12 board will be anchored directly to your house framing and will form the structural side of the deck against your house. The general procedure goes like this: Remove the siding where the header board must go. Tuck flashing up under the piece of siding that remains above this area. Extend the flashing down the side of the house, low enough that it will extend below the bottom of the ledger board once it is installed. This flashing will prevent water from getting behind the framing. 

The ledger board is then attached over the metal flashing with bolts or lag screws. Make sure to seal behind the ledger with caulk to further ensure no moisture can enter. 


Stage 3: Install the Footings and Posts 

Now you will install the vertical posts that will support the beams, which will, in turn, provide the main support for the beam. 


Dig holes to whatever depth is dictated by your building inspection office, then pour concrete and install 6 x 6 or 4 x 4 posts to the required height. Posts can be embedded into the concrete itself, but a better method is to use cardboard tube forms, then embed metal post anchors in the wet concrete at the top of the form. The wooden posts are then attached to these anchors after the concrete dries. 


Whatever method used, it is critical that the posts be exactly plumb, and that they are cut off at precisely the right height as dictated by your building plans. Many builders find it easiest to install the posts first, then cut them all off to the desired height. 


Stage 4: Install Support Beams 

In most deck construction plans, one or more horizontal beams are now installed. These beams will provide support for the joists soon to follow. Generally, the deck joists will be attached on one end to the ledger board with joist hangers and will rest on the other end by a beam that’s supported by the posts you have just installed.

There are many different configurations for posts and beams, so carefully follow your deck plans at this point. A very common method is for beams to be constructed from a pair of 2 x 10s sandwiched together and rested on top of the posts, where they are held in place by metal beam saddles. 


In some deck plans, the beam will be set some distance inside the outside edge of the deck, so that the deck hangs extend the beam in cantilever fashion. In other deck plans, the beam itself may form the outside edge of the deck, forming an anchoring surface to which the joists can be attached.


A very large deck may require two or even more beams to support the heavy load, while small decks require only one small support beam.


Stage 5: Install the Joists 

Now you will install the principle framework of the deck, which includes interior joists spaced every 12 or 16″ apart, as well as rim joists, which form the outside edge of the deck. One end of each joist will be attached to the ledger board with metal joist hangers, while the other end will either rest on top of the support beam, or, in some designs will be anchored to the inside face of the beam. 


Note that all metal connectors and fasteners must be made with corrosion-resistant fasteners and metal connectors. Ordinary galvanized fasteners are not appropriate if you are using pressure-treated lumber, as the chemicals in the wood can corrode them. Make sure to buy screws, nails and other hardware designed to withstand the chemicals. 


Here, too, the spacing of joists and the lumber dimension will be determined both by your deck plans and the requirements of your building inspection office. Very small decks may call for joists built from 2 x 6 timber, while large decks may require 2 x 10 or 2 x 12 timber. Load calculations are very complicated, so make sure to consult your building inspection office on requirements for posts, beams, and joists. 


Stage 6: Lay the Decking 

Now your deck is beginning to take shape and look like the project you envisioned. The next step is to attach decking boards, which will often be 1x 4 or 1 x 6 lumber, or fabricated decking boards with rounded edges. Another option here will be synthetic decking boards, which are notable for their long life. It is quite common to build the deck structure with pressure-treated lumber, then use synthetic decking materials for the visible decking surface and railings. 


Note: depending on the height and style of your deck, you may choose to install stairways and railings prior to laying the surface decking. 


Traditionally, decking boards are anchored to the joists with a pair of screws or nails driven into each joist. However, there are also a variety of “blind nailing” or bracket systems now available that allow you to attach decking boards without violating the face of the boards with screws or nails. Whatever method you choose, make sure to leave a uniform gap between decking boards. This ensures that debris will not get trapped between boards. 


Final Steps 

For many decks, building stairways and railings will be the next step. Many decks other than ground-hugging platform decks will be required by building codes to have stairways and railings. Stairway construction can be quite complicated, especially if a deck is a high one, where a stairway may even need to have a landing part way down. The main deck railings can also involve a complicated system of posts, rails, and balusters, but they also offer an opportunity for style variation. 

You may now be inclined to finish your deck with stain and sealer immediately, but it is often recommended that you wait for a few weeks for this final step, until the lumber in your deck dries out a bit. You should finish your deck before winter sets in but allowing the deck wood to age slightly will help it absorb the stain and finish better. 

By David Beaulieu