Planning a sandwich-panel garage: quantities, construction and total cost

First establish the usable dimensions. Allow space to open car doors, install shelving and walk around the vehicle. Then check the garage-door width and the clear height below its tracks. The finished building’s outside dimensions do not tell you how much room will remain inside.

A sandwich panel forms part of the building envelope and normally rests on a designed supporting structure. It does not automatically replace columns, rails or purlins. Plan the garage together with its foundations and fixings. Also establish the formal requirements for the particular plot: calling it a panel garage does not determine the applicable building procedure.

Walls and roofs face different conditions. A roof carries snow loads among other actions, so it needs an appropriate roof panel and purlin spacing. Do not select a wall panel for roofing merely because its core has the same thickness.

One particular 100 mm PIR wall panel may have a Uc of 0.22 W/(m²·K). A selected roof version can have the same value despite a different cross-section. These are examples of specific configurations. Equal thermal performance does not mean equal load capacity. For a heated garage, assess the whole enclosure, the door and additional losses at junctions. Airtightness and ventilation also matter in an unheated garage.

Assume a garage measuring 6 × 6 m in plan with walls 2.7 m high. This is a measurement example, not a ready-to-build design. Four rectangular walls total 64.8 m². A 2.5 × 2.2 m garage door occupies 5.5 m² and a 0.9 × 2 m pedestrian door another 1.8 m². Subtracting both leaves 57.5 m².

Do not order precisely that area based on subtraction alone. A panel layout is essential. Cutting out the door opening can leave waste that cannot be reused elsewhere. A mono-pitch roof also introduces different wall heights. Measure the actual roof slope, including eaves and required laps. The 36 m² plan area is only a starting point.

Divide the budget into six sections: design and site preparation; foundations and floor; the steel frame or other designed structure; panels, flashings, fasteners and seals; garage door, pedestrian door and ventilation; and finally transport, unloading and installation.

For an illustrative calculation, assume PLN 200 net per m² of panel. At a measured wall area of 57.5 m², the material alone would cost PLN 11,500 net. This is an assumed example price, not a current offer. It excludes cutting losses and the rest of the building. Before deciding, replace it with the selected product’s quoted rate and calculate the actual purchased area. Adding doors, flashings and delivery can substantially change the budget.

Once the foundations are complete, check their level and the fixing positions. Assemble and brace the frame next. Before cladding, verify that supports are plumb, correctly spaced and in the right plane. Do not try to straighten a distorted frame by overtightening the panels.

Subsequent work includes starter flashings, tapes, panels and joint closures. The precise order depends on the system; wall and roof installation differ. Fasteners must suit both the panel and the supporting material. Remove metal swarf afterwards and inspect flashings, seals and drainage. Photograph the work before difficult-to-access areas are concealed.

A simple building shape, repeated panel lengths and a sensible number of openings are the easiest ways to reduce cost. Choosing an available colour also helps. Ordering panels, flashings and fasteners together can simplify delivery. Compare complete material schedules rather than only the lowest unit price.

Do not save money by arbitrarily reducing fastener quantities or omitting seals. A wet car brings water indoors; without air exchange, even a well-insulated garage can become damp. Before signing an order, obtain the panel model, lengths, facing thicknesses and scope of work. Only that level of detail allows a realistic assessment of the finished building’s price.

No. It must, however, be designed for its actual use. An unheated garage still needs proper ventilation and protection against water.

Only as a very rough starting point. Cladding quantities are based on wall and roof areas. Foundations, doors and the supporting structure have separate costs.