T12 trapezoidal sheets: dimensions and suitable applications

TRB 12/1120 has an effective width of 1120 mm and an overall width of 1154 or 1160 mm, depending on the version. Profile height is 12 mm. These figures describe that cross-section, not all products called T12. For a supplementary order, also check edge geometry and the coated side.

Agree sheet lengths for the precise version and thickness. The longest available sheet may not suit the site best. Consider transport, unloading and lifting onto the roof. Production length does not specify the permissible distance between supports.

Assume a roof width of 8 m along the eaves. Dividing by 1.120 m cover width gives about 7.14, so eight strips are required. Do not divide by overall sheet width: part of it is lost in the lap. Eight strips at 1.120 m cover 8.96 m before the verge edges are adjusted.

Profile width affects total cover and the amount trimmed from the edge strip. Width alone is therefore not a sound selection criterion; another roof may produce the opposite result. Draw the strips on a roof plan and include the verge detail. Measure sheet length along the slope, not from the building’s horizontal plan.

Do not confuse the excess cover of the final strip with waste across the entire roof. In the example, eight sheets cover more than the required 8 m. Some material will be trimmed, but the final flashing detail determines exactly how much. Its dimensions are needed for an accurate order schedule.

T12 is available in roofing versions and as wall or ceiling cladding, but the designation alone does not confirm every application. A concentrated-load test at a stated span is not a ready-made batten spacing either. A point load and snow acting over the entire roof are different load cases.

Selection requires a table for the chosen thickness and support arrangement. Check load resistance, deflection and fasteners, as well as bearing width. In refurbishment, measure the existing battens and inspect their condition. Comparing T12 with thicker sheet on a neighbour’s roof proves nothing about suitability.

Do not interpret a test span in a declaration as the required spacing for every batten. It describes the conditions of that test. If no appropriate load table is available, obtain calculations or data from the manufacturer for the intended order. A missing table does not justify choosing an arbitrary distance.

Check minimum pitch for the exact roofing version. If the quotation and instructions disagree, resolve that before buying. Do not adopt the lower angle simply because it suits the building. Obtain confirmation for the actual roof, including sheet length, any joints and lap sealing.

At low pitches, laps, seals and sheet deflection become particularly important. Water drains more slowly and local unevenness can change its route. Do not confuse degrees with percentages: a 10% slope is not 10°. This is a common ordering misunderstanding.

Consider T12 for simple cladding or roofs where the manufacturer permits that version. Its shallow appearance may suit the building, but should not outweigh structural requirements. With wider support spacing, calculate a deeper-profile alternative as well.

T14 is not automatically a better investment than T12. Profile height is only part of the comparison: rib geometry, steel, thickness and cover width also count. Compare the cost of the full roof and substructure. This reveals whether a seemingly cheaper sheet requires additional battens.

Specify the exact model, roof or façade use, thickness and coating. List quantities and each sheet length. Include roof pitch, building location and support spacing. Obtain a price per effective m² and a flashing schedule. Quotations per linear metre require the cover width for comparison.

Do not switch models after receiving a lower price without checking the drawing again. A different profile changes compatibility with seals, flashings and existing sheets. Similar rib height does not ensure dimensional compatibility. Compare physical samples and cross-sections before a supplementary order.

Do not assume compatibility. Different widths may indicate different cross-sections and lap edges.

Yes, if it is a roofing version. Confirm pitch, load resistance and installation requirements for the particular building.