Deck Safety and Structure
Anthony Perry's Inspections will inspect decks as a part of the home inspection. It's estimated that 2.5 million new or replacement decks were built last year. Almost every new home being built today includes an elevated deck or porch. And, existing decks on older homes are being replaced at a very high rate. In fact, the number of personal injuries and deaths related to decks each year is likely to continue to rise because more decks are being constructed each year and existing decks are deteriorating.
FLASHING CAN FAIL
Flashing is another important consideration in deck building. We suggest that builders consider building freestanding decks because this eliminates the potential for water to get into the flashing if it is not installed correctly. When water does leak under the flashing, the wood begins to rot and the deck's foundation is weakened. The homeowner isn't aware of the problem until it's too late and both the deck and the house are impacted by rotten wood.
Many inspectors strongly discourage placing a deck directly under the sill of an exterior door. We suggest about a four-inch distance between the threshold and the top of the deck to keep water from getting under the threshold and eventually rotting out the sub flooring. Holes made in the side of the house, even when filled with a bolt, may allow water to seep in, builders should fill holes drilled for bolts with a durable caulk such as silicone. It's also important to pay close attention to products that are used in flashing. We look for rubber or copper in flashing, and we are working to educate the public on the danger of mixing aluminum flashing with the new treated wood products.
Recent changes in the chemicals used in the manufacture of treated wood have had an impact on materials used in flashing. According to the lumber and fastener industry, the newer chemicals being used to treat wood, alkaline copper quaternary (ACQ) and copper azole, are considerably more corrosive than wood previously treated with chromate copper arsenate (CCA). This means special attention must be paid to fasteners, hangers, and other materials that may come in contact with the wood because aluminum flashing actually deteriorates and dissolves when it comes in contact with treated wood.
RAILINGS ALSO REQUIRE ATTENTION
Because railings are the most visible element of a deck, they offer the builder an opportunity for creativity. They can be made of many materials, formed to different shapes and connected in many ways. However, builders must remember that the railing design must adhere to local building codes that are designed to ensure safety. Typically, if a deck is more than a certain distance from the ground, as little as 18 inches in some areas, railings are required for safety purposes. Codes specify a certain maximum opening between balusters, spindles, or pickets so that a 4-inch diameter ball won’t pass through the railing.
The height of the railing is also regulated, with a height of 36 inches standard for residential properties and 42 or 48 inches most common for commercial and fencing applications. Builders must understand loading and how to properly attach railings. We're particularly leery of installing the vertical guard rail members so that they aren't attached to the deck framing and the top and bottom rails and the verticals are not attached to the deck surface. We’re also seeing some deck builders who are notching the deck posts that extend from the footing and form part of the guard rail to accommodate another member. They don't realize that they are in effect creating the weakest point in that post because of the notch. We advise builders that this do not accept any type of support post with a notch in it.
INSPECTIONS NOW AVOID PROBLEMS LATER
Experienced builders know how much wood moves and what the weather does to wood, even treated wood. Wooden structures built without the benefit of a roof will not last forever, even though the wood is treated to resist the effects of the weather. But, older wood is not always the problem. The inspection is important even before the deck is being built because the structural engineer needs to determine what type of materials are necessary to build that specific porch.
KEEPING UP WITH CHANGES
Building inspectors, like deck builders and homeowners, are challenged to keep up with the deck industry. There are changes to the IRC every three years. State and local amendments are added to those changes. New building materials and deck-related products are appearing on the market in record fashion. Reading industry magazines, consulting with other inspectors on a regular basis, and monitoring state building and code official association Web sites and message boards are all good ways to stay abreast of new products and inspection challenges. And, in some cases, the builder is required to educate the inspector. We see new deck materials and construction methods during on-site inspections and look at manufacturer specifications. We read the industry publications and when we see a new product in the field, we require the builder to provide product information. For instance, if it’s a composite material we need to make sure it is going to span the distances, or if it’s a deck ledger bracket we need to be sure it will support the load it is supposed to. With the new composite materials, we need to make sure that whoever is putting it up is attaching and supporting it the way it’s supposed to be because you can’t support plastic the same way you would wood.
The results of good construction, building inspection, and plan review are often unseen. No one wants to build an unsafe deck and that's what it's all about. And as deck collapses continue to make headlines, the focus on safety and the quality of deck construction is bound to be strengthened.