Every warehouse layout starts with the same conversation, and it is not about racking. It is about the things in the building that are not moving: the columns holding the roof up, the downpipe in the corner, the sprinkler drops, the electrical riser, the dock leveller pit, and the expansion joint running across the floor.

The racking is the flexible part. The building is not. So the layout is really an exercise in arranging a flexible thing around a fixed one, and how well that is done is the difference between a warehouse that stores what it should and one that quietly loses ten percent of its capacity to geometry nobody thought about.

The one rule that decides most of it

Your bay pitch has to work with the column grid, or you lose a bay in every run.

Here is why. Racking is built as a repeating unit: a frame, then a bay, then a frame, then a bay. The beams span between frames, and they span a fixed distance set by the pallet configuration you chose. If a building column lands in the middle of one of those bays, that bay is finished — the beam cannot pass through the column, and the space either side of it is too short to be a usable pallet position.

So the design question is not "where shall we put the racking?" It is "what bay pitch, starting from where, causes the columns to land at frame lines rather than mid-bay?" Get that right and the columns cost you almost nothing. Get it wrong and every single run in the building pays the same penalty, multiplied by however many runs you have.

There are two honest ways to handle a column, and both are used:

Set the run out so columns fall at the frame line. The frame straddles or sits immediately beside the column, and the column effectively disappears into the structure of the run. This is normally the better answer, and it has a second benefit: whatever protection you put on that frame is also protecting the column.

Leave a deliberate gap and let the column sit in it. Where the grid simply will not divide, you build a blind space — a gap between two frames sized to swallow the column and its base. You lose that space, but you lose it once and deliberately, rather than losing a half-bay you keep trying to use.

What does not work is pretending it is not there and dealing with it on installation day. That is how you end up with a run that stops short, a bay with a beam that cannot be loaded, and a layout drawing that no longer matches the building.

Columns are bigger than the plan says

This catches almost everyone, including people who have done it before.

On a drawing, a column is a small square. On the floor, a column is a steel section plus its base plate, plus in many buildings a concrete kicker or encasement around the bottom metre, plus sometimes a haunch where a bracing member comes in, plus the fire protection or the paint build-up, plus whatever has been fixed to it over the years — a socket box, a conduit run, a fire extinguisher bracket, a hose reel.

The base is what matters, because that is where your frame foot has to sit and where your anchor bolts have to go. A column drawn as 200mm can easily be 400mm at floor level once the encasement is measured, and that difference is enough to move a frame, which moves the run, which moves everything after it.

Measure at floor level, in the building, before the layout is finalised. Not on the landlord's plan, which in our experience is frequently the original construction drawing and does not show alterations made since. This is one of the two or three things a proper site survey exists to catch, and it is covered in what a warehouse layout drawing process should actually involve.

A column in the aisle is far more expensive than a column in the run

This is worth understanding as its own point, because the cost is not proportional.

A forklift aisle has to be wide enough at its narrowest point, not on average. A single column protruding into an otherwise clear aisle sets the working width for that entire aisle, and therefore for the runs either side of it. One obstruction, and every bay in that aisle is affected.

It is worse than it sounds, because the aisle you need is not the width of the truck. It is the width the truck needs to turn, position and enter a pallet position, and a driver who has to swing wide around a column loses time on every single pick. Forklift turning radius and aisle width covers how that number is arrived at.

Where a column genuinely must sit in an aisle, it needs protection that is more substantial than a rack guard — a column guard or barrier sized for the impact, not a decorative one. We have written about rack protection, column guards and barriers and what actually survives being hit.

The lowest thing in the room sets your top beam, not the roof

Owners tend to quote the eaves height, or the ridge, and design the racking to it. The usable height is set by whatever hangs lowest over the storage area, and there is usually something.

Sprinkler heads and their drops. Lighting. Cable tray and busbar. Ductwork and fan units. The underside of a roof brace. A crane rail. In a warehouse with a portal frame roof, the haunch at the eaves is lower than the eaves themselves, which routinely surprises people planning a run along an external wall.

Two consequences. First, the top beam level and the load height above it have to clear the lowest obstruction over that run, so a single low duct can cost you a whole storage level along one line. Second, sprinklers have their own clearance requirement that is not negotiable and is checked — sprinkler clearance and racking approval covers what that means in practice, and it is the item most likely to force a redesign late if it was assumed rather than measured.

The practical version of all this is in warehouse clear height and how many racking levels you actually get.

The floor has obstructions too

Less obvious than columns and easier to miss on a walk-through.

Expansion joints. A slab joint is designed to move. A frame baseplate anchored across one will eventually be working against that movement, and the anchors are the part that gives. Runs should be set out so baseplates do not straddle joints — which sometimes means shifting a whole run by a few hundred millimetres.

Drainage channels, trenches and pits. Common in food and industrial units. A frame cannot be anchored over a trench cover, and a drain in an aisle is a maintenance access point that has to stay reachable.

Slab thickness and construction that varies across the building. Extensions and infilled areas are often a different slab from the original, and the anchor specification is not automatically the same across both. Anchoring pallet racking to the floor sets out what has to be established before the first hole is drilled.

Dock levellers and shutter door zones. The area in front of a loading door is not storage, and it is bigger than people allow — it has to accommodate the truck's approach, the leveller's travel and the turning space to get a pallet away from the door and into the aisle. Aligning rack runs with dock doors covers why run direction relative to the doors matters more than almost any other layout decision.

Things above the racking that people forget

Lighting. Fittings that were positioned for an empty shed end up directly above rack runs once the racking goes in, lighting the top of the pallets and leaving the aisles dim. Ideally lighting sits over aisles. Where the racking arrives after the lighting, this is a real and common problem — lighting design in racked warehouses covers what can be done about it.

Fire hose reels, extinguishers, call points and escape signage. These have to stay visible and reachable, which means a rack run cannot simply pass in front of them. Escape routes and exit access in a racking layout covers the ones that are non-negotiable.

If the warehouse is leased

Two extra constraints, and they are worth establishing before design rather than after.

You cannot alter the building. A column, a downpipe or a riser that would be easy to relocate in your own premises is simply a fixed object in a leased unit, and the layout has to accept it.

You may also be restricted in where and how you can drill, and you will normally have to reinstate at the end of the term — which is an argument for fewer, better-placed anchor points rather than for working around a column with extra frames. Racking in a leased warehouse covers floor loading and reinstatement in more detail.

What to expect, honestly

A building with a tight column grid and a lot of services will not yield the same number of pallet positions per square metre as a clear-span shed. That is a property of the building, not of the racking.

So when comparing layouts or comparing buildings, the number that matters is not the floor area. It is the positions the layout actually delivers, and whether the person who produced it walked the floor or worked from a plan. A layout that claims no loss at all around a column grid is usually a layout drawn on a plan where the columns were small squares. How many pallet positions a warehouse will actually take goes through that calculation.

The useful thing to hand a designer is a dimensioned survey: column positions measured centre to centre at floor level, base dimensions including any encasement, the lowest obstruction height over each area, floor joints and trenches marked, and the doors with their clear zones. That one document removes most of the late surprises, and it is far cheaper than moving a run after installation.

What we do is set out on the racking page and the services page.

Planning a layout around a difficult building? WhatsApp us on 9107 2601 — tell us the column grid, the lowest obstruction over the storage area and what truck you run, and we will tell you where the capacity is likely to be lost before anything is drawn.