Roof sandwich panels: decisions to make before ordering

On a roof, the outer facing profile and joint must drain water as intended. A wall panel may use different geometry and fixings. Matching colour and core thickness do not make the two products interchangeable.

Specify the section drawing, rib height, effective cover width and seal positions when arranging flashings. Accessories must suit that geometry. Visual similarity is insufficient, and sealant alone is not a remedy for an incompatible joint.

PIR can provide useful thermal performance where assembly depth is limited. Check the declared U-value of the actual panel against the building requirements. Facings, joints, fixings and the use of the interior also affect roof performance.

Reaction to fire and the fire resistance of a complete assembly describe different properties. PIR does not mean non-combustible; mineral wool may suit some projects. Apply classifications to the actual thickness, orientation and support arrangement, not a general marketing claim.

Core thickness does not automatically include the height of the external rib. Use the complete section when choosing screw lengths and flashing dimensions. An abbreviated invoice description is no substitute for the panel drawing.

The manufacturer specifies minimum pitch for a particular arrangement. End laps and openings may change the requirements compared with an uninterrupted panel. Drainage must remain effective under anticipated structural deflection, not just at the initial setting-out stage.

State the pitch unit clearly in the order. A 5% slope means a height change of 5 cm per metre of horizontal distance. It is not an angle of 5°. Confusing these expressions can lead to an unsuitable roof specification.

The load table must match the core, facing thickness, number of spans and loading conditions. Colour and thermal effects may also matter. Results for another panel or support arrangement cannot be transferred without checking.

Check support width and alignment, with fixings intended for steel or timber as appropriate. Roof panels do not replace the building frame. Rooflights, penetrations and equipment may require extra supporting members, planned before panel lengths are finalised.

Side joints, end laps, ridge and eaves must form a coordinated drainage arrangement. Airtightness on the inside also matters for heated spaces. Pressing panels together does not replace seals of the type and position specified in the instructions.

Protect exposed core edges with suitable closures and flashings. Cutting tools must not damage the steel protection, and swarf must be removed. Follow the manufacturer’s requirements for the sequence and deadline for removing protective film.

Provide roof dimensions, pitch, support spacing and material, openings, thermal requirements and intended use. Compare panels together with flashings, fixings, seals and transport. The panel price per unit area does not show the complete cost.

Before long panels arrive, prepare unloading space, lifting equipment and storage conditions. Protect joints, facings and cores, then inspect connections and surface cleanliness on delivery. Logistics forms part of a properly planned roof specification.