How to choose a roofing sheet colour when the sample and screen disagree

Specify the colour, coating type and finish together. Agree the appearance of flashings, gutters and exposed fixings. For components from different batches, ask to compare samples. Descriptions such as anthracite and dark brown can mean different things to different suppliers.

Take the sample outside. View it in sunlight and shade beside the proposed façade and window frames. Tilt it to the approximate roof pitch. A sheet lying flat on a table reflects a different scene from a roof slope facing the sky, a common cause of surprises after installation.

If possible, view a larger section from a few metres away. A low trapezoidal profile and a deeply formed tile profile cast different patterns of light and shade even in the same colour. A phone photo is a reminder, but automatic white balance and screen settings make it unsuitable as a colour standard.

Compare samples side by side at the same time and angle. Comparing one photographed colour with another physical sample makes judgement difficult because the two were lit differently.

A dark coating generally heats up more in sunlight than a light one with otherwise similar properties. The precise behaviour depends on the finish and surroundings. Long metal components move as temperatures change. The fixing design must accommodate this movement.

Colour is only one influence on roof temperature. Light sheet metal can reduce surface heating, but attic comfort also depends on insulation and a suitable roof build-up. For dark sheets check length and joint requirements. Sandwich panels may also have colour groups with specific installation limits.

Start with long-lasting features such as brick, stone, window frames and driveway paving. A roof occupies a large area, so a slight difference in tone can change the impression of the whole building. On a small building, limiting competing colours on flashings and gutters can help.

Check any local appearance requirements that apply to the site. Availability does not guarantee a colour is permitted. For an extension, compare the new sample directly with the existing roof. Sunlight and dirt may have changed the old finish, even if the colour codes match.

Confirm the chosen finish is available for every component. An unusual sheet colour may be unavailable in prefabricated flashings or accessories. Resolve this before buying the main covering. A near match added later can stand out along ridges and corners.

Agree whether the entire visible slope will come from one batch. Keep the coating specification and a small sample for future additions. With metallic finishes, sheet orientation can also affect the result. Confirm marking and laying instructions for the ordered material.

Compare components under similar lighting with surfaces prepared for inspection. Protective film, dust and sky reflections can disguise differences. If installation is some time away, plan unpacking. First check labels and agreed samples with the supplier’s representative.

If you see a difference, record batch numbers in the delivery inspection and take comparison photos. Hold back from mixing sheets on one visible slope. Assess compliance against the agreed conditions and tolerances. A single sunset photograph is insufficient to decide it.