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.

Bar grating

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.

B-deck with concrete fill

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)

Resin board (structural OSB / engineered wood)

Engineered wood panels — typically 1.125" or 1.5" thick high-density particleboard or composite OSB, 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 — not suitable for cold storage, food processing, or any wet environment
• Higher wear from forklift or pallet jack traffic — typically not rated for wheeled equipment
• 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.

Diamond plate steel

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.

Decking comparison table

How to choose

A three-question decision:

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 load capacity explained: live, dead, and point loads — how decking interacts with load design
• The IBC 2024 mezzanine requirements explained in plain English — fire and sprinkler code path
• Mezzanine cost per square foot in 2026: a complete breakdown — how deck choice changes total project cost