Railing Systems Built for Hawaii's Coastal Environment
Why Anodized Aluminum Railings Outlast Painted Steel in Hawaii's Salt Air
Take a walk around Honolulu and look up at a condominium or hotel built before 1960. Chances are it has concrete balconies about 4 1/2 inches thick, with painted steel railings either welded onto the edge or set in grouted holes. Those railings are losing their battle with the elements. The high airborne chloride content in Hawaii's salt air takes a damaging toll on metals and paint, and after more than six decades, many of these original systems are past due for replacement.
Why Anodized Aluminum Holds Up in Salt Air
In the 1960s, Honolulu builders started using anodized aluminum railings, and most of those installations have fared far better than painted steel. Anodizing is an electrochemical process that forms a protective coating of aluminum oxide on the surface of the metal. It is a hard finish that does not peel or flake. The common specification for railings, windows, and storefronts is a Class 1 anodic coating, a minimum of 0.7 mils thick. At that thickness, it is a durable finish that weathers well, even steps from the ocean.
Fasteners Are the Weak Point
The weak point of older aluminum railing systems in Hawaii is the fasteners. They were either galvanized steel or a mix of ferrous metals and stainless steel. When you see rusty screws holding together a rattly old aluminum railing, you are witnessing galvanic corrosion between dissimilar metals.
In the mid 1980s, the fastener coating industry developed an environmentally friendly process that coats fasteners with a zinc-rich base coat followed by a torque-resistant aluminum top coat. The aluminum top coat provides most of the protection, while the zinc base coat acts as an insurance policy, since zinc is very compatible with aluminum. We use coated 316 alloy stainless steel fasteners on all of our aluminum railing systems and have not seen galvanic corrosion in any of them.
Three Ways to Mount a Railing
Beyond the right fasteners, the other major factor in how long a railing system lasts is how it is mounted. There are three main methods of attachment to a concrete balcony: core mount, surface mount, and side mount. Each has benefits and drawbacks, and for replacement railings, the as-built conditions often dictate which method is used.
Core Mount
A core mount post is set in grout in a cored hole on top of the concrete. The hole is set back from the edge far enough to avoid critical rebar and meet code requirements for strength. This method reduces usable balcony square footage, and if not installed properly, it can allow salt-laden moisture to seep into the grout and electrically connect the aluminum to the rebar in the concrete, causing galvanic corrosion. Epoxy-based grout is a good way to prevent this. If cementitious grout is used, the embedded post should be isolated from the cement with an epoxy coating. Done correctly, core mounting is an acceptable installation method.
Surface Mount
A surface mount post attaches to a base plate fastened to the top of the concrete. We use 316 alloy stainless steel threaded rods set in structural epoxy, which seals the hole and prevents moisture from seeping in and causing corrosion. A hard rubber pad under the aluminum base plate isolates the anodized aluminum from the concrete.
Side Mount
Side mounting is a good option because it increases usable balcony space and provides the most separation between the concrete and the post. The post attaches to the balcony edge with angle brackets or bent plates, isolated from the concrete with hard rubber pads. 316 alloy stainless steel threaded rods are set into the balcony edge with structural epoxy, and additional rods can be placed under the balcony if engineering calls for it. The epoxy seals the drilled holes to keep moisture out.
The Bottom Line for Hawaii Buildings
Anodized aluminum railing systems are a proven choice for Hawaii's aggressive coastal environment, with a long track record of successful installations here and in coastal regions across the country. Keep in mind that when railings are replaced, the new system must meet current building code requirements for height, strength, and openings, which is one more reason replacement projects deserve careful engineering and an experienced installer. The right fasteners, combined with a carefully executed installation, will deliver a long-lasting, low-maintenance system.
If your building's railings are showing rust stains, loose posts, or flaking paint, Seal Masters of Hawaii can assess their condition and walk your board through replacement options.
