How do you check the fire performance of a PIR panel roof before alteration?

A classification for one product cannot be transferred to another. In an existing building, establish the precise panel type and installation arrangement. Neither the colour of the sheet nor a photograph of the core identifies the variant reliably enough to determine which conditions of use its documentation covers.

Reaction to fire describes how a product contributes to the development of a fire. For one range of steel-faced PIR roof panels, the product table gives B-s2,d0 at a thickness of 40 mm and B-s1,d0 from 60 to 160 mm. The example shows why the thickness and precise product designation belong in the specification.

The s and d suffixes also describe smoke production and flaming droplets or particles under the test conditions. These classes give no basis for describing all PIR panels as non-combustible. They do not state how long a roof retains its load-bearing or separating function during a fire.

R denotes load-bearing capacity, E integrity and I insulation under fire conditions. The number gives the time in minutes for which the stated criteria are met. For the PIR range in this example, the catalogue lists REI 30 for thicknesses from 100 to 160 mm. It gives no corresponding rating for the thinner versions.

Check the full classification for the permitted support arrangement, spans, fixings, joints and loading conditions. The rating does not cover arbitrary loads or spans. If the catalogue summary omits these details, obtain the classification document before specifying the roof.

BROOF(t1) classifies the performance of a roof exposed to fire from the outside using a particular test method. It answers a different question from REI or a product reaction-to-fire class. A project may require all three, each supported by its own evidence.

Read which roof covering, build-up and conditions the document covers. An added layer, a changed joint or a new component on the roof may need assessment. Only combine ratings in a roof specification when the documents apply to the same proposed assembly.

Alterations often begin with an opening for ventilation, a rooflight or another service. This interrupts the envelope and may change the support conditions. Detail the framing and seals around the opening to suit its structural role and the fire performance required at that location.

New equipment can increase loads or alter conditions on the roof surface. Check how its fixings will transfer forces into the structure before attaching anything to the facing. Review the structure, connections and fire requirements together before drilling so they can all be addressed in the design.

After significant heat exposure, deformation or delamination, assess the condition of the whole panel. A fresh coat of paint gives no indication of the remaining performance of the core or joints. The scope of any local repair after an impact must also reflect the function of the complete roof assembly.

A replacement section must suit the specified assembly. A panel of the same thickness with a different PIR formulation may have different fire properties. If there is no exact match, agree a revised detail or a larger replacement area after checking the design.

Keep panel identification details, performance documents, the scope of each classification, detail drawings and a record of subsequent work together. Add photographs of joints and penetrations taken before they are concealed. This gives the building operator a basis for the next assessment.

The fire performance of the roof depends on keeping the specified assembly intact throughout its working life. Regular inspections and reviews of proposed alterations help maintain it. When describing the fire performance of a PIR roof, identify the product, the function being assessed and the conditions covered by the classification.