Mezzanine decking options compared: B-deck, bar grating, resin board, concrete

Decking is the horizontal floor surface that sits on top of mezzanine joists. It's the cheapest line item in a mezzanine quote — and the one that most affects how the structure performs in service.

Four materials dominate the market: bar grating, B-deck with concrete fill, resin board / OSB, and diamond plate steel. Picking the wrong one costs more than picking the wrong steel structure, because changing decking later means stripping the floor.

When should you use bar grating on a mezzanine?

Choose bar grating for storage mezzanines: at $3–6 per square foot it's the cheapest option, handles typical 125 PSF loads, and lets sprinkler water pass through — often avoiding a second level of sprinkler coverage.

Steel grate panels — typically welded steel bars on edge, set on perpendicular cross-bars, forming an open grid.

Cost: $3–6 per square foot (galvanized steel, standard 1.25" or 1.5" depth)

Best for:

• Storage operations where you want sprinkler water and light to pass through to the level below
• Light-to-moderate load duty (125 PSF typical)
• Industrial workspace where slip resistance matters more than smoothness
• Operations where the mezzanine is over heavy equipment that needs heat/airflow

Trade-offs:

• Heels and small wheels can catch in the grate openings — not great for offices, retail, or non-industrial uses
• Loose items can fall through to the level below (mitigated by toe boards at edges)
• Higher noise transmission to level below
• Less comfortable for long standing/walking

Fire code: Bar grating is the preferred deck for sprinkler compliance in many storage applications. Because water passes through, often only single-level sprinkler coverage is required (sprinklers below the deck protect the level above and the room).

Load capacity: Standard 1.25" bar grating at 1-3/16" spacing handles ~125 PSF uniform load with joists at 4 foot spacing. Heavier grating (1.5" or 2") for higher loads.

When should you use B-deck with concrete fill?

Use B-deck with concrete fill when people work on the mezzanine full-time or loads run heavy: at $8–15 per square foot installed, it delivers a smooth, quiet composite floor rated up to 500+ PSF.

Corrugated steel decking (typically 1.5" or 3" deep) covered with 3–6 inches of poured concrete to form a composite slab.

Cost: $8–15 per square foot installed (deck + concrete + finishing)

Best for:

• Mezzanines used as office, retail, or assembly space
• Heavy-load industrial use (250+ PSF)
• Forklift-rated platforms
• Operations where dust, debris, or chemical containment matters
• Smooth-floor requirements for casters, carts, or precision equipment

Trade-offs:

• More expensive than bar grating
• Requires structural design that accounts for the concrete dead load (~35–45 PSF additional)
• Sprinkler code likely requires coverage above AND below the deck (water can't pass through)
• Longer installation timeline — concrete cure cycle adds 7–14 days
• Heavier load on the host building's slab below mezzanine columns

Fire code: Solid decking often triggers full sprinkler additions on both sides — this is the largest "hidden cost" surprise on B-deck mezzanines, sometimes adding 30–40% to total project cost.

Load capacity: Designed to specific PSF rating. Common configurations:

• 1.5" deck + 3" concrete fill: handles 125–175 PSF
• 3" deck + 4" concrete fill: handles 250+ PSF
• 3" deck + 6" concrete fill: handles 500+ PSF (forklift class)

When should you use resin board (structural OSB) decking?

Resin board fits budget-constrained, light-load storage: $4–8 per square foot installed for 60–125 PSF duty, and it can't tolerate wet environments — the leading manufacturer states its panels are "not intended for exterior applications" and excludes prolonged standing water from warranty.

One correction worth making, because generic decking comparisons get it wrong: engineered resin panels are not plain OSB, and the branded products are rated for wheeled traffic. Published ResinDek ratings run 2,000 to 8,000 pounds for manual pallet jacks and 500 to 6,000 pounds for AGVs and robots, depending on panel grade and the B-deck beneath — though no grade carries a forklift rating. Our resin deck deep dive works through the tables and the footnotes that qualify them.

Engineered wood panels — typically 3/4", 1-1/8" or 1-1/2" thick high-density wood fiber composite, manufactured specifically for mezzanine use.

Cost: $4–8 per square foot installed

Best for:

• Light-load storage operations (60–125 PSF)
• Budget-constrained projects with limited storage requirements
• Operations where dust or moisture isn't a concern
• Workspaces where some give in the floor is acceptable

Trade-offs:

• Lower load capacity than steel options
• Susceptible to moisture damage and wet environments; branded panels are made in cold-storage grades, but washdown and standing water are excluded
• No forklift rating at any grade — pallet jack and robot ratings apply only to the specific panel and deck gauge specified
• Some products have higher off-gassing — verify formaldehyde and VOC ratings if mezzanine is in an occupied indoor space
• Less fire-resistant than steel grating

Fire code: Combustible deck — many jurisdictions and insurers require additional sprinkler coverage or fire-resistant treatments. Check before specifying.

Load capacity: Standard 1.125" panels at 24" joist spacing handle ~125 PSF uniform load. Lighter capacities (60–100 PSF) work at wider joist spacing for budget builds.

When should you use diamond plate steel decking?

Diamond plate is the heavy-duty pick for harsh conditions — frequent forklift or vehicle traffic and wet, oily, or chemical environments — at $10–18 per square foot installed, the most expensive option, handling 250+ PSF.

Solid steel sheet (typically 1/4" or 3/8" thick) with raised diamond pattern for slip resistance.

Cost: $10–18 per square foot installed

Best for:

• Heavy industrial use with frequent forklift or vehicle traffic
• Wet, oily, or chemical environments where chemical resistance matters
• Areas requiring high impact resistance
• Industrial walkways and platforms in harsh conditions

Trade-offs:

• Most expensive option
• Heavier than bar grating (more dead load)
• Slippery when wet despite the pattern — slip-resistance ratings vary
• Not great for offices or assembly work
• Single-level sprinkler coverage usually adequate (water won't pass through, but if used as walkway over storage the rules vary)

Load capacity: Heavy. 1/4" plate at 24" joist spacing handles 250+ PSF; thicker plates or tighter joist spacing for higher.

How do the four mezzanine decking options compare?

Bar grating is cheapest ($3–6/sqft) and sprinkler-friendly; B-deck with concrete carries the heaviest loads (up to 500+ PSF); resin board is the budget light-storage option; diamond plate handles the harshest industrial environments.

How do you choose the right mezzanine decking?

Answer three questions: what goes on top, what's underneath, and what's the budget. Pallets and bulk storage point to bar grating; full-time people point to B-deck with concrete; vehicles and heavy equipment point to B-deck or diamond plate.

Question 1: What goes on top?

• Pallets and bulk storage → bar grating (cheap, sprinkler-friendly)
• People working full-time, offices → B-deck with concrete (smooth, quiet)
• Vehicles or heavy equipment → B-deck or diamond plate
• Mixed use (storage + office) → split the deck by area, or default to B-deck

Question 2: What's underneath?

• Storage racks → bar grating ideal (lets sprinklers reach storage above and below)
• Production equipment → solid deck for chip/spark containment, dust control
• Other occupied workspace → solid deck for noise and dust separation

Question 3: What's the budget?

• Tight budget, storage use → bar grating
• Budget allows $5–10 more per sqft → step up to B-deck if it improves the operation
• Cost-no-object heavy industrial → diamond plate over B-deck

A mistake to avoid

Don't downgrade decking after design to hit a budget number. The structural design is based on the dead load of the specified deck. Switching from B-deck (40 PSF dead) to bar grating (15 PSF dead) after design means the steel was over-spec'd — you wasted money on steel. Switching the other way (bar grating to B-deck) overloads the joists and may require redesign.

Pick decking first, then design steel to that. Or commit to one with a clear understanding of what change would require.

What to read next

• Mezzanine flooring: the deck layer and the finish layer — what goes on top of the deck: coatings, wet slip resistance, ESD, and moisture testing
• Bar grating mezzanine: load specs and applications — a deep dive on the open-deck option and its NAAMM load tables
• Mezzanine load capacity explained: live, dead, and point loads — how decking interacts with load design
• Can a forklift drive on a mezzanine? — the decking choices that decide forklift-rating
• Wire mesh decking: capacity ratings and the fire-code rule — the rack-beam equivalent, governed by ANSI MH26.2 and explicitly not a walking surface
• Resin deck for mezzanines: ResinDek and its alternatives — the engineered composite panel in depth, with the published load tables and their footnotes