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Do I need to install rigid insulation in the bottom of a walk-in refrigerator before I install tile?

jimjelinski | Posted in GBA Pro Help on

I am being hired to remove the failing metal floor and install quarry tile in the bottom of a commercial walk in refrigerator. The existing floor has 4″ of insulation, then plywood and then metal floor on top of the wood. I believe the existing insulation is in very poor condition and possibly wet and I am planning to remove all of it. This is in a restauraunt in southeren California which is on the second floor of a commercial building where there is a structural slab as the foundation and there is occupied space on the first floor below. The existing metal floor inside the refrigerator is overall about 5″ thick. There is existing quarry tile at the entrance into the refrigerator and the metal floor ramps up inside the rrefrigerator. I have had conflicting recommendations from refrigeration contractors that insulation is and is not necessary in this application. The refrigerators are set for 34-38 degrees. It is not a freezer.

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  1. GBA Editor
    Martin Holladay | | #1

    My instinct (and building science knowledge) tell me that insulation is necessary. But I have no background in the field of walk-in refrigerators, so I don't know what standard practice is.

    If I were involved with this job, I would want: (1) an adequate thickness of rigid foam insulation above the slab; and (2) a waterproof membrane to make sure that spills don't reach the concrete. Moreover, I would want the floor assembly to be detailed by an engineer.

  2. Expert Member

    I've built several walk in coolers for restaurants. The floors were detailed much like the walls, with several inches of rigid insulation sandwiched between the interior and exterior finishes. They are usually under-insulated from an energy conservation perspective, but there isn't much point in beefing up the floor if the walls and ceiling are not comparably thick.
    If it were me I'd put down two inches of XPS, PT plywood and a de-coupling membrane under the tile, which would also help protect against the moisture from the frequent mopping of the floor.

  3. jimjelinski | | #3

    Thank you both Malcomb and Martin. Your knowledge helps me out tremendously. I think that approach is what I will do. Tell me what you think about my specific plan. I think my approach will be to first put down a layer of 1" thick rigid insulation continuous on the complete floor. on top of this layer, I will lay flat pressure treated 2x4s around the perimeter and then another 1.5" layer of same rigid insulation. 3/4 plywood on top of that layer screwed down to the sleepers. At this point, I will install 6 x 6 stainless steel L-metal around the perimeter if the cooler siliconed to the side walls in side the cooler and screwed to the plywood. I will then waterproof the top of plywood and onto the L-metal so that any moisture will never got into the plywood or insulation. Now I will install a 1.5" thick wire reinforced mortar bed and then the quarry tile on top of that. I will also be install quarry tile coved base 6" tall which will essentially cover over the stainless L-metal around the perimeters. Grout will be laticrete epoxy grout.

  4. charlie_sullivan | | #4

    My guess about what you have now is that what you are calling a 5" thick metal floor is actually a metal-faced SIP (structural insulated panel). Most of the 5" thickness is the insulation, with relatively thin metal skins top and bottom. If I'm right about that, you have 8-9" of insulation now. Going from 8-9" of insulation to no insulation would result in greatly increased electricity consumption, a high floor temperature leading to spoilage of food on the floor, and possibly moisture problems in the wood under the floor. I would recommend high-density EPS foam, in a similar thickness.

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