Racking & Storage Systems

Rack type dictates density, selectivity, throughput, and operating cost for the life of a lease. Not a commodity decision.

---

Master Comparison

Rack Type	Selectivity	Depth	FIFO/LIFO	Cost/Position	Density vs. Selective	Best Use Case
Selective (roll-formed)	100%	1 pallet	Either	$40-75	Baseline	High SKU count, FIFO needed, budget-constrained
Selective (structural)	100%	1 pallet	Either	$75-100	Baseline	Heavy loads, industrial, AS/RS applications
Double-deep selective	~50%	2 pallets	LIFO for 2nd	$80-300	+15-20%	Moderate SKU count, density + selectivity balance
Drive-in	Very low (1 SKU/lane)	3-10 pallets	LIFO only	$45-250	+50-75%	Few SKUs, large quantities, date-insensitive
Drive-through	Very low	3-10 pallets	FIFO	$55-250	+50-75%	Same as drive-in but FIFO required
Push-back	Low (1 SKU/lane)	2-4 pallets	LIFO	$150-300	+30-50%	2-4 pallets/SKU, high velocity, lower damage risk
Pallet flow	Very low (1 SKU/lane)	3-20+ pallets	FIFO (automatic)	$300-500	+40-60%	Date-sensitive product, cold storage
Carton flow	N/A (cases/eaches)	4-8 ft deep	FIFO	$50-65/bay	N/A	Pick module fast-movers
Cantilever	100%	Open arms	Either	$65-95/bay	Varies	Long/irregular items: lumber, pipe, furniture
Mezzanine	N/A	N/A	N/A	$30-80/SF	Doubles usable SF	Facilities at 85%+ cube needing more area
Mobile/high-density	100% per open aisle	1 pallet	Either	$90-160	+30-50%	High space cost, cold storage, pharma
VNA (turret truck)	100%	1 pallet	Either	$75-120	+50-75%	Max density in high-bay; requires F50 floor

---

Selective Pallet Rack: Default With Reason

100% selectivity — every pallet directly accessible. The right default when SKU count is high, FIFO compliance is needed, or capital is constrained.

Roll-formed vs. structural:

• Roll-formed: $40-75/position. Standard warehouse applications. Lighter loads.
• Structural (bolted): $75-100/position. Heavy loads, industrial environments, AS/RS applications.

The 85% cube rule: Never design to fill selective rack beyond 85% at peak. Above that: honeycombing accelerates, replenishment congests, errors spike.

---

Drive-In / Drive-Through Rack

Forklift drives into the rack lane to place or retrieve pallets. One SKU per lane — the fundamental constraint.

• Drive-in: Last-in-first-out (LIFO). Single entry point. Lower cost.
• Drive-through: First-in-first-out (FIFO). Entry and exit from opposite ends. Required for date-sensitive product.

Honeycombing risk: Each lane is dedicated to one SKU. When that SKU is partially depleted, the open positions can’t be filled with other SKUs without violating the system logic. Operations with high SKU counts see 30%+ of theoretical capacity eaten by honeycombing.

Best for: Operations with few SKUs in large quantities — seasonal goods, beverage, bulk commodities, date-insensitive product.

---

Push-Back Rack

Pallets sit on nested carts on inclined rails. Each new pallet pushes the previous one back. LIFO — the last pallet in is the first out.

2-4 pallets deep per lane. Safer than drive-in (forklift never enters the rack). Denser than selective. Better for product that doesn’t require FIFO.

Higher cost ($150-300/position) than drive-in — the cart mechanism is the premium. Justified when LIFO is acceptable, damage risk matters (no forklift inside rack), and 2-4 pallet depth per SKU fits the inventory profile.

---

Pallet Flow Rack

Inclined rails with wheels — pallets loaded at the high end, gravity-feeds to the low end. Automatic FIFO. No forklift inside the rack. Can go 3-20+ pallets deep.

Best for: Date-sensitive product (food, pharma, beverage), cold storage (operators stay out of freezer aisles), high-velocity SKUs with FIFO compliance requirements.

Cost: $300-500/position. The premium is justified when FIFO compliance is non-negotiable or when eliminating operator time inside a controlled environment has real value.

---

Carton Flow Rack

Inclined roller lanes for cases and eaches (not pallets). Standard configuration in pick modules.

Cases loaded from the back, flow to the front pick face under gravity. Automatic FIFO. Picker always works at the front face — no reaching into deep shelves.

Pick module pairing: Carton flow + order pickers (low-level) + conveyor takeaway is the standard configuration for case-pick operations. Fast-movers in carton flow, slow-movers in static shelving behind or above.

---

Mezzanine

Steel elevated platform — doubles usable square footage in a facility by creating a second (or third) working level. Vertical space that would otherwise be wasted becomes productive area.

$30-80/sq ft installed. Far cheaper than expanding the building footprint or moving to a larger facility.

Best for: Facilities at or above 85% cube utilization, or operations needing dedicated pick module space (packing, VAS, returns) without sacrificing storage.

Ceiling height dependency: Mezzanine requires sufficient ceiling height above it for working clearance and sprinkler compliance. Standard minimum: 8-foot clearance above mezzanine deck.

---

Decision Framework

1. What are your SKU count and velocity profile? High SKU count + FIFO requirement = selective or pallet flow. Low SKU count + large quantities + LIFO OK = drive-in.
2. What FIFO/LIFO compliance is required? Date-sensitive = pallet flow or drive-through. LIFO OK = drive-in or push-back.
3. What is the cost per position target? Budget-constrained = selective roll-formed. Density premium justified = push-back, pallet flow, VNA.
4. What MHE is (or will be) in the aisle? VNA requires F50 floor and guidance. Narrow aisle reach trucks require 9.5-11 ft. Match rack to truck, not the reverse.