Rack legs put concentrated loads on the slab, so check its capacity before loading. Illustrative photo.
Short answer: a slab designed to NSCP 2015's generic "storage" live load — 6.0 kPa light or 12.0 kPa heavy, per Table 205-1 — has been checked against a uniform floor pressure, not against the real, concentrated point loads a pallet racking system delivers through a handful of small post footprints. Table 205-1 lists no concentrated-load figure for either storage row at all. That gap is exactly where an existing warehouse slab can fail under racking even though it has looked fine for years, and where a new warehouse's floor design has to be driven by the actual racking layout, not a code minimum used as if it were the whole answer.
If you're deciding whether a building you already have — or one you're about to put up — can actually carry the storage density your business plan assumes, this is the check that gets skipped most often, because the slab looks like the least interesting part of the building until it isn't.
NSCP 2015 (National Structural Code of the Philippines, Volume 1, 7th Edition), Chapter 2, Section 205, Table 205-1, "Minimum Uniform and Concentrated Live Loads," lists two storage rows:
| Table 205-1 Category | Uniform Load | Concentrated Load |
|---|---|---|
| 21. Storage — Light | 6.0 kPa | — (none given) |
| 21. Storage — Heavy | 12.0 kPa | — (none given) |
| 12. Manufacturing — Light (for comparison) | 6.0 kPa | 9.0 kN |
| 12. Manufacturing — Heavy (for comparison) | 12.0 kPa | 13.4 kN |
That contrast is the whole point. Table 205-1's own Manufacturing rows carry a code-specified concentrated load right next to the uniform figure, because the drafters recognized that manufacturing floors take point loads from machinery. The Storage rows don't get one — the table simply gives a uniform pressure and stops there.
Section 205.3.1 backs this up directly: "Special provisions shall be made for machine and apparatus loads." And Section 205.3.3 sets the general rule for whichever concentrated loads do apply elsewhere in the table — the default is a load "assumed to be uniformly distributed over an area 750-mm square," positioned wherever it produces the worst effect. Separately, Table 205-2 item 11 requires racks over 2.4 m high to be designed for their total loads, with the lateral seismic force per Table 208-13 — a total-load rule, still not a per-leg figure for your slab. A rack upright's base plate is typically far smaller than 750 mm square, and modern selective, drive-in, and high-density racking wasn't the loading case the storage row was written around. In practice, this means the 6.0/12.0 kPa uniform figure sets a floor-wide minimum, but the racking point load has to be checked as its own load case, sized from the actual rack manufacturer's data — the code doesn't hand you that number for storage.
This is the trap for anyone buying, leasing, or repurposing an existing building: a slab that has only ever stored loose pallets on the floor, or carried light shelving, can look completely sound. No cracks, no visible settlement, no complaints from years of use. None of that tells you what happens once a taller, denser racking system loads that same slab through rack leg footprints instead of a spread-out pile.
The rack manufacturer's base-plate reaction loads (per leg, at your actual configuration and storage height), the aisle layout and post spacing, the slab thickness and reinforcement as actually built (not as originally specified — as-built often differs), and the subgrade/subbase condition beneath it. A structural engineer checks the slab's punching shear and bearing capacity against those actual point loads, not against the generic Table 205-1 storage figure alone.
There is no single verified figure here, and treating one as universal would be dishonest — this genuinely varies by racking system, manufacturer, upright height, beam levels, and the load per pallet position. Manufacturer literature for tall, heavily loaded selective rack frames shows total frame capacities that translate to roughly the mid-tens-of-kilonewtons per post at the upper end, with lighter, shorter frames well below that — the working range cited across manufacturer capacity tables commonly spans from around 15 kN to 60+ kN per upright leg, depending on height and loading. Treat this as illustrative only. The number that matters for your project is the one on your specific rack supplier's base-plate load table for your specific configuration — that is a hold point that has to be resolved with the racking supplier's engineering data before slab design is finalized, not estimated from a blog range.
A slab can pass every strength check and still cause problems for high-bay racking if it isn't flat and level enough. This is a separate discipline from load capacity, measured under ASTM E1155, "Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers" — FF measures short-interval waviness (how smooth the surface is underfoot, over roughly a 300 mm span), and FL measures longer-interval tilt relative to the slab's intended plane (over roughly a 3 m span). A higher number means a flatter, more level floor.
On the classification side, the UK Concrete Society's TR34 standard (widely referenced internationally for industrial floor specification, including for racked warehouses) splits floors into two families: Free Movement (FM) classes for floors where forklifts travel in random directions, and Defined Movement (DM) classes for very narrow-aisle (VNA) racking where trucks run on fixed rails or wire guidance. FM2 is a general-purpose Free Movement class — appropriate for a standard warehouse with normal aisle widths and moderate racking heights, not the tightest tolerance TR34 offers. For true high-bay, very narrow-aisle racking, the relevant tolerance is a Defined Movement class, which tightens further as rack height increases — a taller VNA installation needs a stricter DM class than a shorter one. Specifying FM2 for a very narrow-aisle, high-bay system understates what that floor actually needs to keep the racking plumb and the trucks stable at height.
If your racking plan is standard selective or drive-in racking with normal aisles, a general free-movement flatness class is usually the right target. If it's very narrow-aisle, high-bay racking with guided trucks, floor flatness needs its own defined-movement specification decided before the slab is poured — retrofitting flatness after the fact means re-topping or re-pouring, not a light touch-up.
A quick risk read on whether your slab situation and racking plan need a structural verification before you commit to a storage density. This is a planning-level screen, not a substitute for an actual point-load check by a structural engineer.
Does NSCP 2015 give a floor load number for pallet racking?
No. NSCP 2015 Table 205-1 gives a uniform storage live load of 6.0 kPa (light storage) or 12.0 kPa (heavy storage), and lists no concentrated-load value for either row. Racking loads a slab through small, discrete post footprints, not as a spread-out uniform pressure, so a slab designed only to the tabulated storage figure has not been checked against the actual point loads your racking will apply — that check has to be done separately, using the rack manufacturer's base-plate loads.
Can an existing warehouse slab that looks fine still fail under racking?
Yes. A slab that has only ever carried loose pallets or light shelving, or has simply never been loaded to its design limit, can look completely sound while never having been checked against the concentrated point loads of taller, denser racking. Cracking, punching shear failure, or excessive settlement under rack legs typically shows up only after racking is installed and loaded — by which point the fix is far more disruptive than a design check would have been.
What is FM2 floor flatness and does it apply to high-bay racking?
FM2 is a Free Movement flatness class under the UK Concrete Society's TR34 standard, intended for general-purpose warehouse floors where forklifts move in random directions — it is not the tightest or "superflat" classification. Very narrow-aisle, high-bay racking where trucks run on fixed rails or wire guidance needs a Defined Movement (DM) class instead, which is measured and toleranced differently and tightens further as racking gets taller. Specifying FM2 for a very narrow-aisle high-bay system understates what that floor actually needs.
Does AEDO design warehouse floors for racking outside Negros Oriental?
Yes. Structural assessment and design of a warehouse slab-on-grade for racking loads is a design and engineering service AEDO provides nationwide. Self-performed construction or slab retrofit work is carried out directly by AEDO only within Negros Oriental; elsewhere, AEDO provides the design plus remote oversight of a contractor the client hires locally.
AEDO's role outside Negros Oriental. Nationwide, AEDO reviews an existing slab against your actual racking plan, or designs a new slab-on-grade around your racking supplier's real base-plate loads and flatness requirements, and provides remote oversight of a contractor the client hires locally for the pour. In Negros Oriental, AEDO designs and builds that same slab directly.
Codes and standards referred to in this article, verified directly from primary text where the source is a printed standard.
Not a generic storage-load review — a check run against your rack supplier's real base-plate loads, your slab's as-built condition, and your target storage density.
