How to Build a Deck Part 3: Building
All month long, Dunn Lumber's Jim Coshow and Todd Dermody will be offering insight and resources to help you build the best deck for your home. Check out Part 1: Planning, Part 2: Choosing a Deck Surface, and Part 4: Maintaining.
Now that we've discussed planning and choosing a deck surface, let's discuss the deck-building process. We've included some tips, information, and resources to help you produce lasting results.
Before You Break Ground
Before you start construction, you’ll want to spend some time looking at your specific site and preparing for what’s ahead.
Property Lines, Set Backs, and Right-of-Ways
Any or all of these borders may play a part in determining exactly where you locate your deck. Your local municipality should be able to help you determine these imaginary lines on your property.
Utilities
Sewer, electricity, natural gas, cable, or fiber-optic lines can also inform the location of your deck. If you don’t know where buried utilities lie on your property, you’ll need to find them before you break ground so that the construction of your new deck doesn't damage the utilities or cover them with a permanent structure. Most areas offer free “locate services” where someone will come to your property before you break ground and mark the location of any major utilities. Please be safe! Inadvertently disturbing utilities is at best a major inconvenience and at worst can result in death.
Climate Extremes
If your deck is in close proximity to saltwater, you’ll want to factor that into your plans. Deck boards will receive more of a beating from mother nature if they're located near a body of saltwater and may require more frequent maintenance. More importantly, the metal brackets and fasteners you use in the construction of a deck may need upgrading in this environment. For instance, stainless steel screws are generally recommended near saltwater because of their superior corrosion resistance over standard screws. Be sure to periodically inspect fasteners and perform regular maintenance on decking environments close to saltwater.
Exposure to saltwater may also influence your choice of railing systems. Aluminum railings are a common, long-lasting choice for this kind of environmental exposure, but there are other good choices, too.
Consult a Dunn Lumber decking specialist for more information about best practices for building a deck near saltwater.
Footings (Assuming a Level lot)
If you are building a deck that does not require a permit, using precast pier blocks remains an acceptable solution in most jurisdictions. We still recommend that you pour a small pad (3" – 4" thick) of concrete to place your pier blocks on, as the earth underneath your blocks can tend to settle or shift over time.
The more common method is to pour concrete footings and insert a post support base into the wet concrete. This post base requires 1” of clearance (or standoff) between the post support base and the top of your concrete footing.
For most decks, pouring a footing that is 20” x 20” square and a minimum of 12” deep will meet code requirements. (Make sure the bottom of your hole is level.)
Footing size requirements are all determined by the load above. Really large beam spans or a multi-level deck may require the advice of an engineer. We also recommend consulting a professional contractor or an engineer if you want to build a deck on a sloping lot.
Ledger Connection
The ledger board connection is one of the most important parts of the deck’s framing structure. Its primary purpose is to keep an attached deck connected securely to your home. If you are building a deck that requires a permit, you will want to double-check the requirements in your local municipality. View this PDF for an example of a “deck-to-house” lateral load connection.
Although it's thankfully pretty rare, we do hear stories of decks collapsing around the nation, often causing severe injuries. View a staged example of what happens in a typical deck collapse, and why the deck ledger connection is so critical.
Improperly installed deck ledgers also have the potential to cause significant rot and decay if the ledger board is not flashed properly to keep moisture out of the wall cavity. It's paramount that you pay close attention to this detail.
Framing Lumber
Regardless of the decking boards you choose for your walking surface, use pressure-treated lumber for all posts, beams, and joists underneath the deck. The process of pressure treating lumber helps prevent damage from rot and infestation. It's fortunate that most deck framing is hidden below the deck surface, so most people use a construction-grade treated lumber there. Higher-quality grades of pressure-treated lumber are available for exposed posts or other visible framing. (It is still treated but will be a more visually appealing grade of lumber and won’t have the incisor marks often associated with pressure-treated lumber.)
Certain applications will require more framing lumber under your deck. If you’re planning to place a hot tub or other heavy objects like large planter boxes on your deck, you’ll need extra framing to support the weight. Similarly, second-story elevated decks will require more lumber for bracing. If you're adding features like a hot tub to your new deck, we recommend consulting a professional contractor or an engineer.
Joist Protection
Place a layer of flashing tape on the top of your deck joists. This protective layer guards against moisture and debris that may accumulate in the gap between deck boards, causing unwanted challenges over time. Using flashing tape will improve the likelihood that your treated deck framing remains in good shape—should you ever choose to change out your deck surface in the future.
Railing Post Connections
A railing system is only as strong as the posts that support it. Properly installed rail posts are well anchored to a strong framework below the deck surface. Second- or third-story decks can suffer catastrophic consequences if the connection between your deck framing and railing posts is not done properly. To be compliant with building codes, railing posts must be able to withstand a lateral load of 200 pounds per square foot. Similar to the ledger board connection, double-check the requirements of your local municipality if you are building a deck that requires a permit. Visit this link for an example of a “railing post to deck framing” connection.
Picture Framing
Picture framing is an optional way of installing a trim board around the perimeter of a deck surface. This technique hides the end grain on deck boards while avoiding butt joints, by running boards into a perpendicularly placed board. Picture framing will entail a bit more framing work down below, but it’s often worth it for the clean look.
Handling Butt Joints
If your deck surface design must include butt joints, it is always a good idea that you add (or “sister on”) an additional deck joist below the spot where the ends of two decking boards butt together. This allows each of the deck boards to fully rest on a joist, and not share a single deck joist. Consult the deck board manufacturer’s installation instructions for proper spacing on butt joints.
Cracking, splitting, and other challenges can occur over time with certain products if you install deck screws too close to the end of the board, or at an angle other than 90 degrees to the surface.
As mentioned in the Joist Protection section above, when you install two deck joists side by side, you will always want to install a layer of flashing tape across the top of those two joists so moisture and debris don’t accumulate in the gap and create unwanted challenges over time.
Hidden Fasteners
As mentioned in Part 2 of our series, hidden fasteners are a great option that provide a clean look with no screw heads showing. Different deck board manufacturers often recommend a specific brand of hidden fastener that is compatible with their boards. Some systems tie one board to another in a way which makes it extremely difficult to remove only one, single board after installation. Choose a system that allows you to extract one board without having to disturb all of them—that way you won't be stuck if you ever need to replace or remove a single damaged board.
Pro tip: Methods that use an angled screw through the edge of the board work fine for some lumber and PVC deck boards, but are not recommended for capped-composite boards.
The Cortex hidden fastener system offers a way to avoid clips but still not have the heads of screws showing. A unique bit allows you to drive your deck screws into place and simultaneously create a hole for a plug that is color-matched to your deck board. Tap the plug in place and the screws virtually disappear.
If you're interested in doing more research before you start (which we'd always recommend), the deck tip sheet from mybuildingpermit.com goes more in-depth on many of the things discussed in this post. If you have any questions, be sure to visit one of Dunn Lumber's decking showrooms at any of our nine Seattle-area locations. Our team will be happy to help you find the right decking options for your home.
This series walks through the process of planning, building, and maintaining your deck, to help get your outdoor living space ready for the gorgeous summer weather we have here in the Pacific Northwest. Stay tuned for more tips and resources to help make your next decking project a success.
