A banana packhouse is a traffic building, not a shed
A banana packhouse sits at the end of a transport chain. Fruit comes out of the field on a cableway or in a tractor trailer, is dehanded, washed, treated, boxed, and leaves on a truck.
Each of those transitions happens at an opening in the building, and each opening is a different shape at a different height. That is what makes a packhouse a traffic building: the structure exists to hold those openings in the right relationship.
The cableway arrives high
Where a cableway brings fruit in, it arrives above head height and delivers into the dehanding area. The building has to receive it — an opening at the right height, structure around that opening, and a roof that continues over the arrival point.
The cableway also pulls. It is a tensioned line with a support at each end, and the packhouse is usually one of them. That tension has to be designed into the frame rather than resisted by whatever is convenient.
The truck leaves low and long
The despatch end is the opposite problem: a dock at truck bed height, a canopy over the loading position, and enough turning space for a vehicle that arrived full and leaves full.
The dock is also the hygiene and temperature boundary, so it needs a door that closes. A packhouse that is open to the yard for a whole shift has effectively moved its boundary to the fence.
The building is a one-way flow
Fruit should move in one direction: in at the field end, through washing and packing, out at the despatch end. Backtracking costs handling and damages fruit.
That single rule sets the building's length, and length is what generates the expansion joint question. A packhouse that grows to serve a larger farm will eventually be long enough that thermal movement has to be accommodated rather than ignored.
Washing is the wet part and it is not the whole building
Dehanding and washing use water, and the packing end wants to be dry. The same wet-end and dry-end logic applies as in any fruit packing house, with the wall base and the ceiling as the two places that fail.
Where the two zones meet, the boundary must be a wall and not a change of floor finish.
Height is set by the tallest operation, not by the boxes
Boxes stack low. What sets the height is usually the cableway arrival, the dehanding equipment, and the ventilation needed under a roof in a hot climate.
In a tropical site the roof also has to shed a large volume of rain quickly, and the gutters and downpipes are part of the structure's job.
What I want before drawings
- How fruit arrives: cableway, trailer or both, and at what height.
- The cableway tension and where its other anchor is.
- Boxes per hour, and the truck size and frequency.
- Where washing happens and where the dry side begins.
- Whether the building is expected to grow lengthwise.
- The wind speed for the site in km/h from the applicable local code, not a round number.
Packhouses are usually designed around the packing line and built around the trucks. Reversing that order is the cheapest improvement available.
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: a wet building with a dry end · loadout canopy length and width · raised dock or level entry · a shrimp line is a floor problem
