How G60, G90 and Paint Affect Type B Deck Life on the Coast
Corrosion protection decides how long Type B keeps the steel thickness its load tables assume. G90 galvanizing carries more zinc than G60 and lasts longer in salt air and humidity, so it is the usual choice for coastal Florida. A painted finish improves appearance and adds a barrier, but the coating system should be confirmed for the exposure. We supply G60, G90 and painted Type B.
Why coating affects structure
Type B capacities are calculated from the design thickness of the base steel, 0.0295" at 22 gauge to 0.0598" at 16 gauge. Once the zinc is gone, rust consumes that steel, and capacity and fastener hold drop. Lighter gauges have less steel to lose, so coating choice matters more for 22 and 20 gauge.
Comparing the options
- G60: standard galvanizing for dry, enclosed, conditioned buildings.
- G90: heavier zinc, for coastal sites, open-sided structures, canopies and humid interiors.
- Painted: a factory paint finish for exposed undersides; ask us which substrate and paint system suit your exposure.
- No coating replaces keeping the deck dry: leaks and condensation shorten life more than coating choice.
Choose the right protection
Tell us the site distance from the shore, building use and whether the underside is exposed, and we will quote the coating that fits.
Related Questions
How many years will G90 Type B last near the beach?
There is no reliable single number. Life depends on salt exposure, wind direction, humidity, roof leaks, condensation and whether the deck is enclosed. G90 gives more protection than G60 in all of these. Keeping the roof watertight and the building conditioned does as much for deck life as the coating.
Should I touch up damaged galvanizing on Type B?
Yes. Welding, cutting and handling damage the zinc. Engineers and specifications usually call for zinc-rich touch-up on burned or scratched areas, especially in coastal or humid exposure. Follow the project specification for the touch-up product and extent, and do the touch-up before the roof covers the deck.