Can sandwich panels be used on flat and pitched roofs?

A low-pitched roof is often called flat in everyday language. Material selection needs a specific slope, however, based on the design and actual support geometry. The roof-shape description alone is too imprecise.

A sandwich panel with an upper metal facing forms a jointed roof covering. A PIR insulation board beneath a membrane belongs to a separate waterproofing assembly. Minimum pitches cannot be transferred between the two. Choose the structure and drainage arrangement first, then the appropriate product.

An example system may require 3° for a simple roof without rooflights and 5° where panels have end laps. These correspond to approximately 5.2% and 8.7%. They are example conditions for one solution, not universal minimums. Confirm the complete joint, penetration and support arrangement for the selected panel. Another system may have different requirements.

These figures do not apply universally to every panel. Another range may need a different slope or detail. Nor can extra silicone replace the required fall. A joint must function as intended by the system. Too little slope can alter drainage and watertightness conditions.

Percentage fall is the height difference divided by horizontal distance, multiplied by 100. An angle in degrees expresses the slope differently. Therefore, 5° does not mean 5%. This is a common mistake with small roofs.

For a horizontal distance of 6 m, a 3° angle gives a height difference of about 31.4 cm; at 5° it is about 52.5 cm. These are geometric calculations without deflection or construction tolerances. The design must also establish sloping panel length, eaves and bearings. Do not order solely from a plan-view dimension.

A long panel can reduce transverse joints but needs suitable logistics and structural conditions. Where joining is necessary, specify cutbacks, laps, seals and supports. Use details from the selected model’s documentation.

Do not transfer lap lengths from a different panel type without checking. The same applies to rooflights and service penetrations, each of which interrupts the uninterrupted roof field. At low slopes, drainage around them is especially important. The detail must match the system’s profile, fixings and seals.

Over a load-bearing substrate, separate PIR insulation can be installed beneath suitable waterproofing. This differs from a finished roof panel with steel on both sides. Specify the vapour-control layer, joint layout and fixings. Boards intended for a dry assembly need protection from water during work.

A PIR board with thin aluminium facings is not itself the external roof covering in this arrangement. The designed waterproofing drains the water. Slopes, outlets, overflows and flashings are specified separately. An apparently flat roof still needs proper drainage. Low insulation water absorption cannot replace a watertight layer or suitable substrate.

On a pitched roof, panels, fixings and structure still require checking. Snow and wind loads matter, as do panel lengths and facing colour. Load tables are used to select the precise arrangement.

A steeper roof also changes installation and maintenance access. Plan protective measures and material handling. Do not treat a panel as an unrestricted working platform. Permitted use follows from the design and instructions. Correct pitch is only one condition for a safe roof.

Before installation, check levels and support alignment. Afterwards, inspect joints and drainage clearance. Deflection, local depressions or incorrectly positioned flashing can retain water despite the correct design angle. Installation instructions help organise the inspection.

Keep gutters and outlets accessible. Inspect for accumulated debris during maintenance. Suitability for flat or pitched roofs is therefore conditional: documentation must cover the designed slope, joints and loads. That decision can be checked against data, rather than judged from a photograph alone.

Do not assume so. The specific model’s minimum slope and all manufacturer conditions must be met.

No. An angle of 5° corresponds to approximately 8.7%. State the correct unit in the design and order.