G60 vs G90 Type B Roof Deck: Which Costs More and Why?
G90 costs more than G60 because it carries more zinc: under ASTM A653, G90 means 0.90 oz of zinc per square foot (total, both sides) versus 0.60 oz for G60. That extra coating gives longer corrosion protection, which is why G90 is common in humid and coastal Florida. We supply Type B in both and quote them side by side.
What you pay for
The steel, gauge and profile are identical; only the zinc coating weight changes. The cost difference depends on the steel and zinc markets when you order, so compare G60 and G90 on the same quote for your project rather than with a rule of thumb.
Which to choose
- G60: common for interior, conditioned spaces where the deck stays dry once the building is enclosed.
- G90: favored near the coast, in high humidity, in open structures such as canopies and parking areas, and where the spec calls for it.
- Painted: a finish option when appearance matters; confirm the base coating with your spec.
- The architect or engineer of record sets the coating in the deck specification.
Price both options
If your spec allows either coating, ask us to quote G60 and G90 together from the same takeoff so you can see the real difference on your job.
Related Questions
Does G90 change the deck's strength?
No. The coating protects against corrosion but does not change the structural properties. Section properties and load tables in our catalog are based on the steel's design thickness and 50 ksi yield, which are the same for G60 and G90 versions of the same gauge.
Is G90 required in Florida?
Coating is set by the project specification and engineer, not by a single statewide rule. Coastal exposure, humidity and whether the deck is in an enclosed space all factor in. Many Florida specs call for G90, so check your deck section before ordering.