How can I build the safest deck for my clients?
When building a deck, the most important safety check is to make sure you’re up to code. The DCA 6 prescriptive deck building code and the recently released International Residential Code (IRC) contain everything you’ll need to know, from joist size to ledger attachment. When building, consider future maintenance. What type of wood preservative treatment are you planning to use? Different treatments will have different corrosive impacts on fasteners. When you are looking at the durability of fasteners, note where you are using them. Are they ledger or lag screws or are merely securing the deck boards? When installing life-safety fasteners, think about how difficult it will be to inspect, replace or repair those fasteners. Weigh initial cost vs replacement cost. Also consider any manufacturer recommendations specific to the wood deck you are building.
What should I look for during annual inspections?
Once a deck is built, keep it in great shape with regular maintenance and annual wood deck safety checks. These, along with proper maintenance and periodic refinishing will extend the life of the deck. This is especially true if you live in parts of the U.S. with heavy snow and moisture. A well-maintained deck can last twice as long as a neglected deck, with a life expectancy of up to 20 years.
In addition to continued compliance with building codes, missing connections are the number one warning sign of an unsafe deck. Go underneath the deck and examine how it’s put together. That starts with the ledger board, which fastens the deck to the house. Then, make sure posts, beams, joists, deck boards, railings, fasteners and connectors are all stable and in good condition. Remove fasteners and inspect, looking for patterns of corrosion. (A white and frosty appearance shows that a fastener has reached the end of its life.) After assessing your client’s deck substructure, be sure to check the flashing – an L-shaped piece of metal that diverts water and is on top of the ledger board. If the flashing is degraded, has holes, or is missing, replace it or have a new one installed.
What is the most common inspection/installation error?
Deck or guardrail collapse is rarely if ever caused by occupant overloading: the number one issue is lack of deck maintenance, decay or erosion of fasteners. The most common installation errors are related to the ledger board and flashing. Faulty installation allows water to enter and collect around the house, resulting in rot and decay. When installing and inspecting, make sure that you have proper drainage between the deck and the house. Also ensure that you are using the correct fasteners for the job. Nails are not enough. A safe deck features the use of heavy-duty, metal hardware throughout the entire structure, spanning from the house to the posts in the ground.
What’s changing with the 2021 IRC?
The pre-engineered design tables have been completely overhauled in a number of ways.
- Snow loading. The structural components in a deck can now be prescriptively sized for more than just a 40-psf live load, with the addition of 50-, 60-, and 70-psf snow loads in all of the design tables.
- Tributary area. Table R507.3.1 has been expanded to provide a smaller, 5-square-foot area to size from, bringing the minimum diameter down to as small as 8 inches.
- Post sizing. Table R507.4 was greatly expanded, allowing for variables such as snow load, species, and tributary area of deck supported. The common 4×4 post can now, under certain circumstances, extend as high as 14 feet.
- Beam design. Table R507.5 was modified to include single-ply beams in all listed species, including redwood and cedar.
- Joist span. Table R507.6 was reorganized to better present the variables of joist span and joist cantilever. In addition, the “one-fourth-the-backspan” rule for joist cantilevers is easier to use because you only have to check the value in the table and not the value in the table and ¼ the backspan. More importantly, the change allows for more customized design. The previous table assumed the largest backspan; now you can use the actual back span of your deck.
Another major change to IRC guidelines is the distinction between guards and handrails. Guards prevent falling from one elevation to another, whereas handrails provide stability on stairs, etc. The minimum live load table, R301.5, now separates these features, primarily so the loading direction of guards can be independently evaluated. Until the 2021 IRC, guards have had to resist 500-lb. loads in all directions, which has resulted in some robust connection details that wouldn’t be necessary for an inward load. Under the 2021 IRC, guards will no longer be required to resist forces pulling inward or upward.