When is a T12 profile suitable and how many sheets do you need?

Record the dimensions, building location and planned supports. Note whether the interior is heated and how much moisture to expect. A shallow steel profile provides no insulation on its own. For a garage, design the wall or roof around its actual use and internal conditions.

In this example the 12 mm profile has an overall width of either 1154 or 1160 mm, depending on the version. Both cover 1120 mm. For a 6.20 m wide area, 6.20 ÷ 1.120 is about 5.54. Order six strips and trim the edge to suit the layout; a fraction of a full-width sheet cannot cover the last strip.

Six strips give 6.720 m of cover before cutting. Draw how the surplus width will be divided. The rib position matters next to a door or at a corner. Repeat the calculation using the actual cover width for any other T12 section.

Measure at several points and check the diagonals. If a wall is out of square, the last sheet may need a tapered cut. Allow for this in the cutting plan and edge detail. Keep the specified side laps consistent across the wall.

On a façade, a sheet may run between the bottom and top flashings. On a roof, measure along the slope. In both cases allow for the agreed termination when ordering the cut length. An arbitrary allowance of several centimetres can interfere with the detail.

Check the route from the vehicle to the fixing position. Long sheets can buckle if poorly supported during manual handling. Shorter lengths create extra joints. Agree a manageable format with the installer.

Sheet behaviour depends on steel thickness, trapezoidal geometry, material grade, supports and fasteners. Two products of equal thickness can have different allowable loads. Use the load table for the exact section.

Check the chosen sheet at the support spacing shown on the drawings. If the supports are unsuitable, the design may need different supports or another profile. A nominal thickness of 0.70 mm is no guarantee of capacity. Coordinate sheeting and structure before manufacture.

End laps require particular care on shallow slopes. Overlap length, sealing method and minimum permissible pitch depend on the system. Figures for a different shallow profile are insufficient to specify T12.

Establish whether sheets will cover the full slope or meet at end laps. Include flashings at walls, chimneys and eaves. If the permitted use is unclear, obtain confirmation for the precise configuration before purchase. Adding sealant on site cannot extend the product’s declared application.

Add fasteners, flashings, seals and delivery to the sheet price. On a small shelter these can account for a substantial share. Price the structure and underlying layers separately. Compare packages covering the same usable area and performing the same function.

Provide dry storage and suitable supports for the pack. Material delivered weeks before installation needs different arrangements from sheets delivered to a prepared structure. A delivery date matched to the work may be more valuable than a small discount for collecting the entire order at once.

Specify who will cut the edge sheets. Ordering factory-cut lengths may still leave edges to fit to an irregular outline on site.