A dairy is a wet building wrapped around cold rooms
A dairy receives raw milk, heat treats it, and moves it into cold storage before dispatch. The receiving and processing side is wet and warm. The storage side is dry and cold. They are usually under the same roof.
That adjacency is the design problem. It is not difficult, but it is easy to get wrong by treating the whole building as one environment.
Receiving is the wettest room in the plant
Milk arrives in tankers, is pumped out, and the receiving area is washed down afterwards. Hoses run, floors are flooded, and the wash water carries milk solids that dry to a film.
Receiving also has to handle the vehicle. A tanker needs a bay it can back into, a platform at the right height, and enough turning space that it does not have to reverse twice. Those are traffic decisions that constrain the structural grid before anything else is settled.
Cold rooms want the opposite of everything else
A cold store needs an insulated envelope, a vapour barrier, and a floor that does not heave. It does not want washdown water, high humidity or warm air reaching it.
Where a cold room sits inside a steel building, the insulated panel does the environmental work and the steel frame does the structural work. The mistake is to let the steel frame do both — a steel wall with insulation added later will condense on the cold side and the problem will appear as corrosion behind the lining, invisible until it is advanced.
The junction between the wet processing hall and the cold store is where this is decided. A separate wall, a drained threshold and a lobby between the two costs little at design stage.
Cleaning in place repeats several times a day
Pasteurisers, lines and tanks are cleaned in place with hot water and caustic. The frequency is what makes dairy different from a plant that is washed once a shift: the slab is wet more often than it is dry.
Falls, gullies and a plinth at every column base are the three details that decide whether the steel at floor level survives. A coating chosen for "food grade" without reference to the actual chemical is a coating chosen by label rather than by specification.
Refrigeration plant is a machine room, not a corner
Compressors and condensers are heavy, they vibrate, and they need airflow. Placing them in a corner of the processing hall because there is space there is how a dairy ends up with a hot spot, a noise problem and a maintenance complaint.
A separate plant room or an external plant deck solves all three at once, and gives the refrigeration contractor a clear boundary.
What I want before drawings
- The process flow with wet and dry zones marked separately.
- The cold room sizes, temperatures and whether they are inside the frame.
- The tanker access and turning envelope.
- The cleaning regime and the chemicals used.
- Whether refrigeration plant is internal or external.
- The wind speed for the site in km/h from the applicable local code, not a round number.
Dairies are usually built to a known process, which is an advantage: the layout can be settled early and the building designed around it rather than adjusted afterwards.
Written by Johnny Joe, who advises owners and project managers in Africa and South America on steel buildings. If this decision is live on a project, send the layout and the constraint that worries you and I will tell you what it changes.
Related: zoning a wet process · a comparable wet production hall · corrosion class as a selection input · how milk arrives and leaves
