Most homeowners probably don’t give much thought to the systems that hold up their house and their decks. It is usually assumed that once a deck is designed and built, it should last almost forever without too much required maintenance or attention. Recently, I observed the ramifications of that line of thinking on a 30-year-old deck. It is quite possible that the boards on the deck had been replaced, but no one ever thought to look too closely at the hangers. Hangers are metal supports that you typically see on wood decks that are used to support the deck joists. The loads of people walking around on the deck are typically transferred from the deck surface boards to the joists, to the joist hangers, and the hangers are attached to perimeter beams or ledgers. All of the wood in an exposed, outdoor environment, should be pressure treated or suitable for the environment, and, likewise, the deck hangers should also be able to withstand some of those harsh conditions. The hangers that are circled in red (although difficult to see because of the paint) have completed rusted through and provide no support to the joists.
It is hard to say exactly what caused these hangers to rust completely through, but, without that support point, there is no telling how the deck shown is really being supported. It is likely that these deck hangers fell victim to some common forms of corrosion (such as being painted or being put into contact with pressure-treated wood and chemicals used for ice melt) or were inappropriately selected from the start. Just as you would not necessarily use pressure treated wood inside your home because it wouldn’t be exposed to the same environment as it would be outdoors, your builder might not use the same hangers inside and outside of your home for various reasons. The problem is that the visual differences in the hanger products are less obvious than a treated vs. untreated piece of wood. Can you tell the difference between a galvanized piece of metal and one that isn’t galvanized? How about between galvanized and powder-coated? Or painted and powder coated? The point is that going to a hardware store and grabbing something that looks right, may not provide the same longevity or support as the correct product would supply.
As previously mentioned, hanger manufacturers warn about the corrosive effects of various treatment products for wood, paints used on certain metal surfaces, and also products such as ice melt or salt when they come into contact with metal fasteners or hardware. For example, one manufacturer points out that stainless steel fasteners or hardware should never be painted as it impacts the ability of the stainless steel to form a natural oxidized protective coating. This allows rust to start forming on a surface that, because of its material properties, would not normally rust. The manufacturers generally supply a number of similar-looking but differently coated or treated hangers depending on the application. Knowing how the hangers may be used and installing them in appropriate conditions could be the difference between a deck that lasts a few years and a deck that lasts a few decades.
To make sure that you get the longest life out of your deck and hardware, be sure to select the correct hardware (or retain a designer, such as EVstudio) and also perform the routine maintenance needed to keep your deck safe!