There is more to building a deck than wood, screws, nails and hammers. To make a deck safe and long-lasting there is a great deal of vital structural standards that have to be met. From the size of joists to the depth of footings and the type of fasteners, there are huge safety and quality benefits in having an expert build your Salt Lake deck. (Learn about deck building codes here.)
“Decks cause more injuries and loss of life than any other part of the home structure. Except for hurricanes and tornadoes, more injuries may be connected to deck failures than all other wood building components and loading cases combined.” – Don Bender, director of the Composite Materials and Engineering Center at Washington State University
Building Code Violations Can Lead to Disaster
To ensure safety there are local and state building codes that have to be met when building a deck. It is estimated that only about 50% of the current 40 million existing decks are code compliant. This could be due to codes being updated and improved over time, but it could also be that some decks were improperly built. The most common deck building code violations include proper fastening of the deck to the house, proper fastening of the railing to the deck, post-base connections, openings in railings (4” max).
When it comes to building codes and deck safety, it is often the connections that can wreak the most havoc. These are the most critical connections for deck safety and longevity: (Click for detailed information on each of these connections.)
Permitting, Codes & Inspections
One of the most important benefits of using an expert deck builder in your outdoor remodel project is the permit. Licensed contractors are required by state law to have a permit if it is required for a project. If not, they can be fined and lose their license. A good contractor will obtain the permit for the homeowner and usually have a great depth of knowledge in regards to the inner workings of the local building department, which can help them streamline and even speed up the process.
When is a permit required?
A permit is required (in most cases) if one of the following criteria is true:
- A deck is attached to the house.
- The deck is larger than 200 square feet.
- Permitting applies even if the project is a replacement of an existing deck.
What does having a permit mean?
A permit is proof that the design specifications meet the building department’s requirements. It does NOT mean that your project is built to specification until the building department inspects the progress and signs off on it. The local building department will usually inspect a minimum of twice.
- When the holes for footings are dug, before being poured. This will ensure the depth of the footings are large enough to support the structure without falling.
- At job completion. This ensures (among other details) that proper hardware is used, tension ties are installed, and railing heights are sufficient.
Other Critical Deck Construction Items
There is a great deal of seemingly small details that can affect the safety and quality of deck construction. In deck building, everything matters.
- Hardware: Galvanized hardware will cost pennies more per piece, but lasts years longer for exterior application and should always be used in deck, porch, pergola and other outdoor living space construction.
- Joists: Your joists are the main support structure holding all of the weight of your deck. Do you want wood, pressure-treated or steel? Consider this information along with your project and your budget to make the best-informed decision:
- Standard fir wood works well for most typical applications of decks in Utah, as our climate is dry enough.
- Pressure-treated should be used in low-to-grade applications (less than 18” from the ground), as there is not enough air flow to dry out the standard wood causing it to rot. Using pressure-treated wood adds about 40% to the cost of the lumber.
- Steel joists are for applications where longevity or special strength is required. Steel joists are lighter, straighter and carry a 25-year warranty, just like composite decking. They are triple the price of a typical wood board but are the best option in certain applications.
- Contractor Relationships: Does your contractor have relationships with the right people? Anyone can go to a lumberyard and buy wood, screws, and decking. Archadeck cultivates relationships with local reps from Simpson, FastenMaster, TimberTech, Trex, and other industry leaders in order to know the most up-to-date construction methods and hardware available. Many of these items only add a few dollars to the cost of the deck while strengthening it far beyond any loads that it will see. Some of these methods even save labor and money.
Critical Deck Connection Details
Ledger to House & Lateral Load Connection
The ledger board is what attaches to the house. Most deck failures occur by the deck pulling away from the house.
- If the contractor is nailing ledger to the house it will pull out, lag screws and washer or engineered structural screws are the proper building method.
- Are lag screws at the proper distance apart (typically 12”-16” on center, staggered up and down)?
- Last few code revisions have required tension ties
DTT2Z – standard for several years, installation requires one on each end of the deck with a threaded rod to another attached inside the house. Downside is that if the basement is finished, requires cutting into ceiling and patching.
DTT1Z – Simpson’s newest offering that meets code. Two required on each end of deck, with one within 24” of edge of deck. Advantage is installation requires a lag screw or engineered screw to attach to house from outside only.
Joists to Ledger
How are the joists attached to the ledger? Is the contractor toenailing the joists to the ledger? Or is he using joist hangers, which is the safest method?
- Toenailing the joist is not acceptable in Utah. To meet code, hangers are needed as toenailing barely meets the necessary strength, which is not good for long-term stability.
- What type of joist hanger is the contractor using? Is he placing a 2×10 in a hanger made for a 2×6?
Is the contractor using a double-shear joist hanger? Standard joist hangers have nails straight into the ledger and straight into the joist. Double-shear hangers utilize a crossing pattern for the joist nails that go through the joist and cross behind it in the ledger board, creating a stronger hold to the ledger. They cost approximately $0.30 more per hanger and exponentially increase the capacity of the deck.
- Are all nail holes filled in the joist hanger? Any missing nails will reduce the rated capacity of the hanger.
- Are the joist hangers galvanized?
Joist to Beam Connection
How are the joists connected to the beam? Are they simply sitting on the beam, or toenailed into the beam, or are structural ties used?
- Hurricane ties are the best way to secure joists to the beam, especially with the high winds that we see in Utah. There are multiple types to choose from, depending on the load requirements.
Blocking in span of joists strengthens the joists and resists any torquing of joists. Many older decks have blocking over the beam, which isn’t required anymore, especially with hurricane ties. Effective blocking will be located close to the midpoint of the joist.
Beam to Post Connection
- How is the beam connected to the posts? Many contractors will forego connectors and simply toenail beams into the post with nails, lessening stability. Several types of connectors are available depending on post and beam sizes to have the most solid connection possible.
- Correct beam construction: A typical beam is made of two 2x boards spanning the posts. If a typical 4×4 post cap is used, this 2x beam is too narrow to fit properly. Some contractors will use a ½” plywood in between the 2x boards to make it the correct size. Unfortunately, this simply traps water in between the boards and promotes rot over time. Special post caps are available to properly fit this type of construction and a variety of other atypical beam designs.
Footings: Post to Concrete
Lately, we have seen several decks where the footing size was insufficient for the size of the deck it was supporting. This results in the deck sinking or the footings starting to shift. Either can cause failure of the entire deck with no warning.
- Are footings being used? We also see many decks where the posts are simply sitting on top of a concrete patio. This is insufficient to support the deck. Usually, this is evident by the concrete cracking or a section of the concrete tipping.
- How deep are the footings required to be? Most areas in the valley are a minimum of 30” and increase as elevation increases. At higher elevations, footing requirements are 42” or more. This is to get the footings below the frost line. If footings don’t extend to the frost line, freezing and thawing of the ground during the winter can cause footings to heave and cause damage to the deck structure.
- How wide are the footings required to be? This is directly correlated to the size of the deck and number of footings. If the footings are too small, the weight of the deck will push the footings down into the soil and cause the deck to sag (best case) or even fail (worst case).
- Are the correct post bases being used? Depending on whether concrete is already existing or being poured as part of the construction, there are several options to attach it to the footing. The biggest concern here is that the base is sized to the correct post size (4×4, 4×6, 6×6, etc.) and that the post is either pressure-treated, or the base keeps the post 1” off of the concrete footing. This helps to alleviate rotting potential on the wood.
Railing to Deck
This is the most important part of the entire railing construction.
- How is the post connected to the deck? Is it nailed or screwed in or does it utilize connectors that are rated to withstand forces called out by code?
- Nails and screws do NOT have sufficient strength to hold in rail posts. Nails will pull out, and screws will either pull out or snap when any force is put on them.
- Depending on the post construction, either lag bolts or engineered connectors are the best way to connect a railing post properly.
Stair Stringer to Deck & Stair Tread to Stringer
Stringers are the boards that run from the deck to the ground and are cut to hold the treads.
- How are the stairs connected? Many stringers are simply nailed to the deck and will quickly pull out of the deck. Either engineered screws or stair connectors are the preferred way to connect to the deck.
- Are the stairs sloped properly? The max height of a stair is 7-3/4”, with a minimum depth of 10”. Also, all stairs must be within 3/8” of each other.
- Is the bottom of the stairs pressure-treated? Just like posts, untreated wood must be at least one inch off the ground to avoid rot. Stair stringers should either be made completely from pressure-treated 2×12 wood, or rest on a pressure-treated board.
- Are the stairs properly supported over long spans? Stairs that are over seven treads must either have a mid-span post or be strengthened by sistering (doubling) the stringers. This not only makes the stairs feel sturdier but lengthens their life.