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Walk-in floor rebuilt from the subfloor up

Client: Commercial kitchen
Collage of four photos from the walk-in freezer floor build: plywood subfloor, cutting the diamond-plate deck, welding a seam, the finished floor
Scope
Walk-in floor build: plywood subfloor and a diamond-plate deck, every seam screwed down and sealed
Timeline
May 2026
Location
New York City
Year completed
2026
What was delivered
  • Plywood subfloor cut, fitted and fixed inside the box shell
  • Diamond-plate deck panels cut to size on site and fitted tight to the wall panels and door threshold
  • Perimeter joint sealed
  • Deck seams screwed down and sealed, corners included

The call

A commercial walk-in got a new floor, done properly. Not patched and not overlaid: built from the subfloor up, inside the existing box.

Most of our work is repair. This one was a build, and the sequence is the whole story, so it is laid out here in the order it happened.

Why the floor is the hard side of the box

A walk-in floor is the bottom face of an insulated box, and it has the hardest job of the six sides. It carries rolling loads, takes every spill, gets mopped, and it still has to hold the cold in above the slab. This one went down as a plywood subfloor for a flat, fixed base, with a diamond-plate deck on top to take the traffic.

The build, in order

  1. Subfloor. Plywood sheets cut and screwed down to make one flat, fixed base inside the box shell.
  2. Deck. Diamond-plate panels cut to size outside next to the truck, then carried in and fitted tight to the existing wall panels and the door threshold, protective film still on.
  3. Perimeter. The joint between deck and wall panels sealed.
  4. Seams. Every joint in the deck screwed down and sealed, including the corners.
Plywood subfloor sheets being cut and screwed down. The base has to be flat and fixed before anything goes on top of it.
Plywood subfloor sheets being cut and screwed down. The base has to be flat and fixed before anything goes on top of it.
Subfloor down inside the box. The walls are the existing insulated metal panels.
Subfloor down inside the box. The walls are the existing insulated metal panels.
Diamond-plate deck panels cut to size on the sidewalk beside the truck. There is no room to do this inside the box.
Diamond-plate deck panels cut to size on the sidewalk beside the truck. There is no room to do this inside the box.
Deck panel fitted tight to the wall panel and the door threshold, protective film still on. The perimeter joint is sealed as each panel goes in.
Deck panel fitted tight to the wall panel and the door threshold, protective film still on. The perimeter joint is sealed as each panel goes in.

Why the seams decide whether it works

Every joint in the deck was screwed down and sealed, including the corners, which is where people get lazy because nobody sees them. An open seam is a path for water to get under the deck, and water under a walk-in floor does not dry out.

Sealing a seam in the deck, so mop water and spills stay on top of it.
Sealing a seam in the deck, so mop water and spills stay on top of it.
The finished floor: seams sealed across the deck and into the corners, wall panels and door frame untouched.
The finished floor: seams sealed across the deck and into the corners, wall panels and door frame untouched.

Equipment and materials

BoxExisting walk-in shell, insulated metal wall panels, kept in place
SubfloorPlywood sheathing, cut on site and fixed to the base
DeckDiamond-plate tread panels, cut to size on site, film-protected during fitting
SeamsScrewed down and sealed on every joint, corners included; perimeter joint sealed

What this means if you manage the building

One crew carried the whole scope: the carpentry and the metal deck, cut and fitted on site. For a general contractor writing a walk-in spec, the line that matters is the seams, corners included, because a floor that lets water under it, or leaks cold, does it every hour of every day.

From the job log: Building a walk-in floor from the subfloor up (8 Sep 2026).

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