Hollow Metal vs Wood vs FRP: Choosing a Commercial Door
, by United Doors and Locks, 3 min reading time
Steel gauge, core construction, moisture and fire rating — how to pick the right door material for what the opening actually has to survive.
Three materials cover most commercial door openings: hollow metal, wood and fiberglass reinforced polyester. They are not interchangeable, and the right choice usually comes down to what the opening is exposed to rather than what it costs up front.
Hollow metal
A hollow metal door is two formed steel face sheets welded or interlocked over an internal core, with reinforcement channels at the hinge and lock locations. The core may be honeycomb, polystyrene, polyurethane or mineral board depending on whether the door needs insulation or a fire rating.
Steel thickness is given in gauge, and lower gauge means thicker steel. 18 gauge is the common commercial standard. 16 gauge is heavier and used where abuse is expected. 20 gauge appears on lighter interior work. Frames follow the same logic, typically 16 or 14 gauge.
Use it for: exterior openings, stairwells, mechanical and electrical rooms, service corridors, and almost any fire-rated opening. Hollow metal carries the widest range of fire ratings and takes hardware abuse better than anything else at the price.
Watch for: corrosion. A standard hollow metal door is primed steel and needs painting and maintenance. In wet or coastal environments, galvannealed steel is worth the upcharge — and even that will eventually give up somewhere a fiberglass door would not.
Wood
Commercial wood doors are flush doors with a face veneer or laminate over a solid core. The core matters more than the face: particleboard core is the common institutional standard, structural composite lumber core holds screws and hardware better, and mineral core is what allows a wood door to carry a fire rating.
Use it for: interior openings where appearance matters — offices, classrooms, patient rooms, hotel corridors, anywhere the door is seen more than it is abused. A stain-grade veneer door reads as finished architecture in a way a painted steel door does not.
Watch for: moisture. Wood doors are interior products. Put one in an exterior opening or a humid space and it will warp, delaminate or swell out of its clearances. They also dent, and a dented veneer is not repairable the way a dented steel face can be filled and repainted.
FRP
FRP doors have fiberglass reinforced polyester face sheets bonded to a rigid core over a perimeter frame that may be fiberglass pultrusion or treated wood. The colour is impregnated through the face rather than painted on, so scratches do not expose a different colour underneath.
Use it for: wet, corrosive and washdown environments — pool equipment rooms, car washes, food processing, chemical storage, coastal exterior openings, marinas. FRP does not rust, does not rot, and does not need painting.
Watch for: two things. Cost, which is higher than hollow metal for the same opening. And fire ratings, which are more limited than hollow metal — if the opening needs a rating, confirm the specific product carries it before specifying.
Choosing quickly
- Exterior, or fire-rated, or likely to be kicked — hollow metal.
- Interior and it needs to look good — wood.
- Wet, chemical or coastal, and you are tired of replacing rusted doors — FRP.
One thing worth saying plainly: the frame material does not have to match the door. A wood door in a hollow metal frame is a completely normal commercial assembly, and it is what most interior openings actually are.
Not sure which way to go?
Tell us what the opening is exposed to and we will tell you what will still be there in ten years. Call 346-777-3031 or email sales@uniteddoorsandlocks.com.