Multi-tier mezzanines. Two and three decks where the building cubic supports it.

Where it fits

When clear height beats floor footprint.

A multi-tier mezzanine is the right answer when the building is tall (24 ft+ clear, ideally 30 ft+) and the operation can use vertical density — racking by levels, picking by zones, or a manufacturing flow that can stage between decks. The trade-off vs. a single tall mezzanine: lower clearance per deck, more access points, and tighter sprinkler / egress design.

Common configurations

• Two-tier storage — the most common; pallet storage above, rack-supplemental below, with shared columns and footings.
• Two-tier mixed — storage above, work platform below (or vice versa); separate egress design per deck.
• Three-tier — only in tall buildings (30 ft+ clear); typically all storage with bar-grate decks for sprinkler coverage to grade.
• Tier + catwalk — primary deck plus catwalk service routes between adjacent equipment platforms. See catwalks.

What changes vs. single-tier

• Sprinkler coverage — intermediate decks block sprinkler reach to lower levels. Bar-grate decks (open mesh) restore sprinkler coverage; solid decks require an in-rack sprinkler system.
• Cumulative egress — OBC §3.4 sums occupant load across decks for egress count. A 60-occupant single tier might only need one stair; a 60-occupant + 50-occupant double tier almost always needs two.
• Column loads — bottom-tier columns carry every deck above; foundation footings are sized for cumulative load, not per-deck.
• Clear height per deck — typically 8 – 10 ft per tier vs. 12 ft+ for a single mezzanine.
• Forklift access — usually not feasible above the first tier; pallet drops or VRC service required.

Typical parameters

• Building clear height required24 ft (two-tier) / 30 ft+ (three-tier)
• Per-deck clear8 – 10 ft
• Live load per deck125 – 250 psf typical
• Deckbar-grate (sprinkler) / B-deck + concrete (top tier)
• Egresscumulative across decks
• Lead time6 – 10 weeks from sign-off