Sandwich panel building in Batumi: warehouses, workshops and pavilions

How a sandwich panel is made

A sandwich panel consists of two sheets of galvanised steel with a polymer coating and a layer of insulation between them, bonded together at the factory into a single board. Wall panels join with a tongue-and-groove lock, while roof panels have an outer sheet with high ribs and are laid with an overlap down the slope. The factory cuts the panels to length for the design, so a warehouse wall can be clad with vertical panels running its full height, without horizontal joints.

The properties of a panel are set by its insulation:

The frame and how the panels are fixed

A panel encloses the building, but it doesn't hold it up. The load is carried by a steel frame: columns, trusses or beams and bracing, with sheeting rails on the walls and purlins on the roof, to which the panels are fixed. The structural engineer chooses the spacing of the rails and purlins from the panel manufacturer's tables for the wind and snow loads on the plot. At the corners of the building and along the edge of the roof, the wind off the sea pulls harder at the cladding, so the supports for the panels are closer together there than in the middle of a wall. The building gets its stiffness against wind and tremors from the frame bracing, and in the calculation the panels act only as cladding. How the frame itself is protected from corrosion and fire is described on the page about steel frame construction.

For a garage or a storeroom the frame can be made of box section steel, while for a warehouse or workshop it is rolled steel sized by calculation. Around the perimeter we build a concrete upstand above the ground for the panels to sit on: the bottom edge of a panel must not stand in water after a downpour or take knocks from wheels and shovels.

Joints, fixings and edges: where a panel lets in water and cold

The panel itself doesn't let water or cold through: its weak spots are the joints and the holes. During installation we keep an eye on several things:

• sealing tape goes into the lock of a wall panel on the inside and sealant on the outside, otherwise warm, humid air from inside the building escapes into the joint, and moisture settles on the cold sheet;
• screws with EPDM washers are tightened so that the washer is pressed down but not squashed flat, and on the coast we use screws with a heavy-duty coating or stainless steel ones;
• panels are cut with a saw or metal shears, never with an angle grinder: hot sparks burn through the coating around the cut, and a year later rusty dots appear on the sheet;
• the protective film on the face side is removed on the day of installation: under the summer sun its adhesive bonds into the coating within a few weeks;
• corner, window and ridge flashings are lapped in the direction the water runs, and the side laps of roof panels are sealed with sealant.

The site foreman photographs every junction, especially where doors, windows and the roof meet the wall, before the flashings cover it.

Fire and thickness: what we use for warehouses, workshops and shops

We choose the insulation of the panels according to the fire requirements in the design and to what will be kept inside. Walls between fire compartments, walls next to a neighbouring building, rooms holding combustible materials and spray-painting areas are built with mineral wool panels. In the other walls and on the roof, where the design allows it, PIR can be used: at the same thickness it is warmer, and the panel is lighter. We don't put expanded polystyrene panels in warehouses or workshops, even when they are cheaper: in a fire polystyrene melts and burns in drips, and the fire spreads along the wall inside the panel. How fire compartments and separation distances are built into the design is explained on the page about warehouse construction.

We work out the panel thickness from the conditions inside. An unheated warehouse needs only a thin panel, a heated warehouse, shop or workshop needs a thicker one, and a cold room needs the thickest of all, with special locks. There is no point in using a panel thicker than the calculation requires: heat escapes through the joints, the doors and the floor, and extra centimetres of insulation won't fix that.

Where sandwich panels fit, and where they don't

Panels work well where you need fast assembly, a large open hall and warmth without wet work: a warehouse, a hangar for machinery or boats, a workshop, a production building, a car wash, a shop or retail pavilion by the road. They also suit small buildings next to a house: a garage, a storeroom, a site cabin for the duration of a build.

We don't offer panels for a premium home, a villa or a guest house. Thin steel sheet rings in a downpour and when it is struck, a dent in the facade stays for good, the wall does almost nothing to stop sound between rooms, and even with cladding the building reads as a utility building. Temporary accommodation for workers or a watchman's hut in panels is acceptable. In rooms with constant moisture, such as a car wash or a food production area, we use panels with a coating made for that environment and plan the ventilation from the start. Where a forklift operates, the bottom of the walls is protected by a concrete upstand or an impact barrier.

Doors, windows and new openings in a panel wall

A panel carries only itself and the wind, so every opening in the wall is framed with steel posts and a header tied into the main frame. Sectional doors are hung on this frame, doors and windows are fitted in it, and the panels above the opening bear on the header, not on the door leaf. The structural engineer needs the opening sizes and the door types before the steel is ordered: the tracks and the operator take up space under the roof, and a truss must not run into them.

Around an opening the panel is cut, and the insulation is exposed at its edge. We cover the edge with a shaped trim with a seal, and at the doors we build a threshold with a drip, so that water from the yard doesn't run in under the bottom panel. A new opening in an existing wall is also possible: the panels are cut out to the marking, and a frame and trims are fitted, but first the structural engineer checks that the opening won't interfere with the frame bracing.

How much a sandwich panel building costs in Batumi

The shell of a heated sandwich panel building, such as a warehouse, workshop or shop, costs from 580 to 780 ₾ per m². The price includes the column foundations, the steel frame, wall and roof panels, gutters, flashings and trims, and installation. The floor, doors and building services are priced as separate lines, and so are the design and the utility connections.

A turnkey warehouse with an industrial floor, doors and lighting costs from 840 to 1,080 ₾ per m². Cladding the walls of an existing frame with panels costs from 120 to 155 ₾ per m² of wall, and sectional doors with an automatic operator from 7,200 ₾ per opening. A turnkey 4×6 m steel frame garage with sandwich panels costs from 25,200 ₾, and an insulated sandwich panel cabin for a storeroom or a site cabin from 10,800 ₾.

Costs go up with mineral wool panels in fire walls, thick panels for heated conditions, coatings and fixings for the beachfront, and a long span. A simple rectangular building of one height costs less. We send a preliminary estimate based on the dimensions and purpose of the building within 24 hours on business days. The final cost is set on the basis of the design, after a visit to the plot and once the estimate is agreed, and in the contract we break it down by stage.