Choosing a roof covering for an industrial building

Span widths, the purlin layout, the roof geometry and the location of the building are needed. The temperature and humidity inside must be defined, as must the technological processes. Thermal, acoustic and fire requirements matter. Without this information an offer can only be compared superficially.

Attach a plan of the rooflights, penetrations and equipment to the specification. Openings and point loads change the way the roof performs. It is also worth stating the intended method of cleaning. A coating suitable for a dry warehouse need not be appropriate for a room with aggressive vapours.

It is useful when an insulated enclosure assembled from prefabricated elements is required. The outer profiled facing sheds water, the core provides insulation and the lower sheet forms the interior surface. All these parts work together as a defined product.

Selection requires checking the load tables for the actual facings and the span layout. A thicker core is not the only condition for loadbearing capacity. Lengths, supports and fixings also matter. A wall panel of similar thickness is not an acceptable substitute for a roof panel without appropriate documentation of use.

In a roof with separate layers, a deep structural steel profile can form the loadbearing substrate. A designed vapour control layer, insulation and waterproofing are laid on it. This solution allows the individual functions to be selected separately. It does, however, require a coordinated design for the entire roof assembly.

Structural trapezoidal sheets differ from thin covering profiles. T18 or T35 should not be chosen on the basis of their name alone, with any purlin spacing assumed. Calculations of loadbearing capacity and deflection are needed, along with a fixing design. The behaviour in the zones of openings and equipment must also be checked.

PIR can provide favourable thermal resistance at a smaller thickness. Where the roof has a limited layer height, this can be a significant advantage. Mineral wool may be needed because of fire or acoustic requirements. EPS and other materials are considered where they suit the complete solution.

Do not compare equal thickness alone. Check the declared lambda or U-value of the specific element and the other requirements. Water absorption, point loads and compatibility with the waterproofing also affect the selection. Insulation is not a material for the arbitrary support of heavy technical equipment.

The reaction of a material to fire and the fire resistance of the assembly describe different properties. The core designation does not automatically determine the class of the whole roof. A classification covering the specific variant, the facing thicknesses, the joints and the support conditions is needed.

The requirements for external fire exposure and for service penetrations must also be checked. A change in the support spacing or in a detail may go beyond the scope of the document. The highest class stated in a catalogue should not be treated as a property of every panel in the same family.

The profile geometry, the side joints and any longitudinal laps matter. The required minimum slope may differ for a continuous panel and for a roof slope with rooflights. The values apply to a specific system. They are not transferred between manufacturers or different models.

Flashings, seals and fixings must form a compatible system. When planning lengths, transport, lifting and thermal movement must be taken into account. Dark facings may require additional restrictions. Water should have a clear path to drainage even at local obstacles.

Set two complete assemblies with the same requirements side by side, including installation. For a roof panel, add the flashings and seals; for the trapezoidal sheet, add all the layers above it. Include lifting equipment, transport and protection of the works against the weather. The price of the sheet alone does not give a reliable result.

At handover, the joints, fixings, drainage and condition of the coatings are checked. The product documents and a record of changes must be kept. The maintenance plan should cover access to the rooflights and equipment. An industrial roof is to function as an efficient assembly throughout the building’s service life, including after subsequent changes to the equipment.

In the offer table, add columns for: support spacing, facing thicknesses, declared U-value and the scope of the fire classification. The entry ‘PIR panel 120 mm’ alone is not enough to compare technically equivalent proposals.

The covering of a hall is selected together with the structure and the protective layers. A sandwich panel and a roof on a structural trapezoidal sheet can perform a similar function but require a different design. A full specification allows them to be compared fairly in terms of loadbearing capacity, tightness and cost.