Deck installation can be a fun project, but it’s important to make sure you’re doing it correctly to avoid structural failure. You also want your deck to be safe and comfortable.
Most decks are made from wood, such as pressure-treated pine or cedar, but exotic hardwoods like ipe and cumaru and even composite materials can be used. Contact Deck Builders Baltimore County for professional help.
Joists form the base for your deck frame, supporting the beams and holding up the decking. The quality of your joists will affect the longevity and durability of your deck. To ensure they’re strong enough, joists should be sized correctly to suit the size and load of your deck. Proper spacing can prevent sagging, warping and structural problems down the line.
To make sure your joists are long-lasting and sturdy, they must be well-treated with a protective sealant. This will protect against water penetration, rot and insect infestation. When applying the sealant, it’s important to follow the directions on the label. The sealant should be brushed on and allowed to dry for at least 24 hours.
After the joists are treated, you can begin building your deck frame. First, fasten 2×4 rim joists to the ledger using hidden fasteners. Next, install joist hangers on each end of the ledger and rim joists. Joists should be spaced 16″ on center, and if they have a crown (a slight hump along the edge of the board) install them with the crown pointing up toward the sky.
Use a level to make sure the joists are straight and even. Then, nail the joists to the bearers with corrosion-resistant nails or screws. April says it’s a good idea to screw into the ends of the joists as well, as this will help secure them and keep them from loosening over time.
After you’ve installed the joists, it’s time to add the stair stringer and railings. To do this, snap a chalk line across the center of your joists and use it as a guide for laying out bridging material. Alternating blocking is one method; this involves installing blocks in an alternating pattern between joists, which allows for easy insertion of nails or screws. Another option is straight-line blocking, which involves placing all the blocks in a straight line.
Beams
A deck must be supported at its foundation. Typically, this means digging footers and pouring concrete before installing posts and beams to support the deck. Beams take the load off joists and transfer it to the posts and into the ground, so it’s critical to get them right.
If you’re building a deck on your own or with help, it’s always best to double-check the location and height of posts and bracing before beginning to frame the deck with joists. It’s a lot easier to rework these things before the beam is in place than when you’re standing on a ladder holding a 2×8 over your head!
Start by marking joist spacing (16” on center) on the beams and ledger. Then notch the posts as needed to accommodate the beams, using a notched post bracket at each hole. Once the footers are set, you can install the beams and their brackets.
Beams can be either drop or flush and are a key element in how the deck will look, as they create the structure that holds up the decking and stair stringers. A drop beam also allows you to cantilever the joists over the beam, creating a much larger deck with the same number of posts and beams.
If you’re not sure which type of beam to use, check with your local building code. Both have their advantages and disadvantages, but generally speaking, a drop or girder-style beam is better than a flush style. Once the beams are in place, you can install the decking and stairs. And don’t forget to add the appropriate structural hardware, which will be a combination of joist hangers and shoulder brackets.
Stairs
Stairs are an integral part of a deck’s design. They add a functional element while allowing people to move throughout the home and emphasize its surroundings. Straight stairs to patio or lawn landings are an easy DIY build for homeowners, while simple curved steps create a more dramatic look. Regardless of their style, deck stairs must meet residential building codes to be safe for use. This requires careful attention to detail, including double-checking measurements and ensuring that the rise and run of each stair is consistent.
A stair’s substructure is comprised of two main components: treads and stringers. Treads are the horizontal boards you step on as you climb or descend the stairs, and they must be firmly fastened to the stringers to ensure stability. The stringers are wider boards, typically 2x12s, that run at an angle from the deck’s framing to the landing pad and support the stair treads. They can be either open or closed; open stringers have notches, while closed stringers are solid boards with cleats for the treads attached to the side.
To ensure that the stringers are adequately supported, they’re typically connected to the deck joists using a board called a ledger. This helps to distribute the load of the stair stringers and prevent them from buckling or warping, especially when they’re exposed to moisture. A ledger board can be made of pressure treated pine or a stronger composite material. Regardless of the material, it’s important that it be preservative-treated to protect against mold and mildew.
Ledger
The ledger is one of the most critical framing components in any structure and is a major part of deck construction. It distributes load evenly and provides stability to the structure. Using the right type of material for your ledger is important. The ledger must be made from a durable, rot-resistant wood such as pine or pressure-treated pine. It must also be secured to the house or building in a secure manner. The most common method for attaching the ledger is to use lag bolts. Incorrectly attaching the ledger can have catastrophic consequences.
Using the wrong fasteners for attaching the deck ledger to a wall can lead to the deck collapsing, or a structural failure within the house or building. Lag bolts must be installed according to the requirements of the International Residential Code 2021, Table 507.9.1.3(1).
Deck ledgers must be attached to the rim joist of the house with hex-head bolts or lag screws that have a minimum diameter of 1/2 inch. They must be staggered to accommodate the maximum gap between the sheathing and the house floor band joist that is permitted by the IRC.
It is also a good idea to install flashing around the deck ledger and cladding to prevent water from penetrating through the sheathing and into the wall cavities or studs of the house or building. This prevents rot, mold, and other serious problems.
In addition to lag bolts, there are other fasteners that can be used to secure the deck ledger such as concrete anchors, HDG expansion bolts, or stainless steel concrete screw anchors, but check with the anchor manufacturers for installation instructions and fastener spacing tables. If the deck ledger is attached to a concrete block foundation, you must use anchors that are approved by the local building official for this application.
Structural Hardware
Deck framing and its components are a major part of any elevated deck construction project. Framing errors may cause serious structural problems and injuries. This is why it’s so important to follow building codes and manufacturers’ instructions when framing a deck. Joist hangers, rim joists, and ledger boards are the most essential pieces of hardware needed when constructing a deck.
To create a sturdy structure for your deck, you need to make sure that the joists are spaced correctly. A good starting point is to mark the first floor joist at 8 inches on-center, then 16 inches on-center toward the end joists. This will ensure that there is a minimum of two deck planks per joist, and that the joists will be able to support your weight without sagging or cracking.
Joist blocking or bridging is also a critical piece of hardware for your deck. Blocks made of the same type and size of lumber are installed between each joist to tie them together, and help distribute the load evenly across all joists. This reduces joist deflection, which is when a joist bows up or down, causing a dip or hump in the deck surface.
Flashing is an essential waterproofing material that should be installed above and behind the ledger board, ensuring a watertight connection. This will prevent water from infiltrating the ledger and house, which could cause rot and moisture damage.
To prevent swaying, bracing straps should be installed on the side of the deck that sits directly under a drop beam. These braces, available in both T and L-strap styles, will greatly strengthen the post-to-beam connection and prevent swaying during strong winds.