Painting Warehouses and Industrial Space

A house has a handful of surfaces. A warehouse in the light-industrial parks of El Cajon, Santee or the National City bayfront can have five or six on a single elevation: tilt-up concrete panels, a strip of concrete block, steel roll-up doors, painted steel columns and bollards, galvanised flashing, and inside, an open ceiling of steel deck, joists, conduit and ductwork twenty or thirty feet up. Each one fails in its own way, and each one is prepared in its own way. Treating the building as one big wall is how industrial paint ends up peeling within a couple of seasons.

What makes industrial painting different from a large house?

The surfaces and the height. Steel rusts, galvanising repels paint, block soaks it up and concrete is alkaline. Every one of those needs a specific primer before any finish goes on. Then there is access: much of the work is overhead, so lifts or scaffold are part of the plan, and the floor below has to be protected or cleared.

Steel: rust, mill scale and the right primer

Steel doors, columns, stair rails, bollards and structural members are where rust shows first, especially near the coast. On the bayfront in National City, salt on the air finds every chip in a coating. Inland in El Cajon and Santee there is less salt, but more sun, and a dark steel door facing south gets hot enough to stress any finish.

Rust has to be removed back to sound metal, by hand or power tool depending on how far it has gone, and the clean steel primed the same day before it starts to flash-rust again. A coating over live rust looks fine for a while, then lifts in blisters as the corrosion keeps spreading underneath. Product categories matter here: rust-inhibitive metal primers and direct-to-metal coatings both exist for this work, and Sherwin-Williams and Dunn-Edwards each make industrial lines in those categories. The label, not habit, decides which goes on which metal.

Galvanised steel is its own problem

Galvanised flashing, rails and door frames look like they should take paint well. They do not. New galvanising is smooth and often carries oils from manufacture, and some coatings react with the zinc and let go in sheets. The surface is cleaned thoroughly, sometimes lightly abraded, and primed with a product rated for galvanised metal. Weathered galvanising that has dulled to gray usually grips better than new, but it still needs cleaning first.

Concrete block: filler first

Concrete masonry units, the gray block common on older warehouse walls and screen walls, are porous and full of pinholes. A finish coat rolled straight onto bare block soaks in unevenly and leaves the wall looking spotty and rough. A block filler goes on first to close the surface, and on block it is often the coat that does the most work.

Block also shows efflorescence: white, crusty salts pushed to the surface by moisture moving through the wall. It is brushed and washed off, and the wall is allowed to dry. If it keeps coming back in the same place, there is a water source, and that is worth finding before money goes on coating. Masonry primers made for high-pH surfaces, such as the Sherwin-Williams Loxon line, exist as a category for this kind of wall.

Tilt-up concrete panels

Many newer buildings are tilt-up: concrete panels cast flat on site and lifted into place. Two things matter. First, the panels can carry residue from the form-release and curing compounds used when they were poured, and paint will not bond over it; a thorough wash is the start. Second, concrete is alkaline, and fresh concrete especially so. A primer suited to masonry, applied once the label’s conditions are met, protects the finish from that alkalinity. The joints between panels carry sealant that moves with the building, and failed joint sealant is worth raising at the estimate, since replacing it is its own line in the scope.

High ceilings and open structure

Inside, the ceiling is usually the biggest single area and the hardest to reach. Exposed steel deck, joists and ductwork are normally sprayed, because brushing around that much structure is impractical. Two points shape the plan:

• Dry-fall coatings. This is a category of ceiling coating designed so that overspray dries in the air before it reaches the floor, settling as a dust that sweeps up rather than wet paint on racking, stock or machinery. It is often the reason a ceiling can be painted while a building is still partly in use.
• Access. Lifts or scaffold are planned around the racking layout and the floor’s load, and the floor below is either cleared or covered. Ebenezer is certified in Scaffold Safety, Fall Protection and Respirator Training with Medical, and access is part of the schedule.

Roll-up doors and dock areas

Steel roll-up doors flex every time they open, so the coating has to tolerate movement, and the slats are cleaned of grease and grime before priming. Door tracks and moving parts stay masked. Loading-dock bumpers, bollards and curb edges are often done in safety yellow or a contrasting color, and those are high-wear areas that may want a tougher coating than the walls.

How a warehouse job is sequenced

1. Walk the building with whoever runs the floor, and agree what can be cleared and when.
2. Clean every surface by its type: wash concrete and block, degrease metal, remove efflorescence.
3. Repair: rust removal, block and concrete patching, notes on joint sealant.
4. Prime by surface: metal primer on steel, galvanised-rated primer on zinc, block filler on block, masonry primer on concrete.
5. Mask doors, tracks, fixtures, signage and anything that is not to be painted.
6. Apply the finish, ceiling first when the interior is included, then walls, then doors and trim.
7. Walk it together before the lifts leave the building.

Before you ask for a bid

It helps to know which surfaces are involved, whether racking can be moved, what hours the floor runs and whether any area must stay operational. More on how larger properties are handled is on the commercial painting page, and if the floor itself needs a coating, see epoxy floors. For what the climate does to buildings out east, the El Cajon page covers the heat.

An industrial building rewards the painter who gets the primer right on every surface. Ebenezer is a licensed C-33 contractor, number 1120008, issued to Lemoon’s Painting Inc, who manages each project personally and is ready for larger work. Ask for a free estimate and he will walk the building with you, surface by surface, and tell you what each one needs.