What does a roofer do and how can you assess their work?

Carpenters build the timber structure. Roofers install the roofing layers and covering, while sheet metal work includes forming and fitting flashings. One crew may cover several trades, but confirm the division of work. Misunderstandings often arise where one trade hands over to another.

Specify stripping the existing roof, preparing the substrate, installing the underlay, battens, covering, flashings and drainage. Set out insulation and the internal airtight layer separately. The words ‘complete roof’ leave too much open if the parties have different work in mind.

The contractor should know the instructions for the particular profile and coating. T18 and T35 trapezoidal sheets and modular tile-profile sheets have different support and jointing requirements. Batten spacing, laying direction and fixing positions must suit the product. General experience with metal roofing alone tells you little about this.

Water management at chimneys, valleys and eaves matters just as much. Ask the roofer to explain where runoff from the covering will go and how the layer beneath it will drain. If the answer relies entirely on applying plenty of sealant, discuss the detail more closely.

Use cutting tools approved by the sheet manufacturer so heat does not damage the coating. Suitable hand or electric shears are typical. An angle grinder with an abrasive disc can damage the finish beyond the cut edge. Hot particles left on the roof can become starting points for corrosion.

Control screw tightening and remove swarf as work progresses. The crew must plan how to transport, lift and support the sheets safely. Sheets should not be left in wet, unventilated packs. These arrangements need to be in place before anyone steps onto the roof.

Ask for examples of roofs with a similar shape and the same covering system. An even roof plane viewed from the street shows only part of the job. Look at chimney flashings, verge finishes and gutter layout. Photographs taken before concealed work was covered are also useful.

Ask how the contractor dealt with a difficult detail on a previous job. Years in business alone say little about that. Experience laying straightforward trapezoidal sheets may not extend to every modular system. Sandwich panels likewise require knowledge of their joints, lifting methods and specific fasteners.

Describe the materials, scope, programme and basis of payment. Agree who will order components and check quantities. Specify what happens if damage to the roof structure is uncovered. Agree the price or basis for charging for extra work before it is carried out.

Distinguish the contractor’s workmanship warranty from the manufacturer’s material warranty. A manufacturer’s document does not automatically cover installation errors. Keep the delivery specification and instructions for the products purchased. They can help establish the cause of a later problem.

Agree how the house will be protected between stages. Rain may arrive while part of the old covering has been removed and the roof is still open. Plan temporary protection and the order in which areas will be stripped. Name a contact who can make a decision if the weather changes.

Arrange inspections in stages. Before work is covered, inspect the substrate, continuity of the layers and difficult junctions. At completion, check the covering, flashings and fixings, and verify that ventilation and drainage paths are clear. Obtain photographs of important details and a written record of agreed corrections.

The client does not need to walk on the roof to inspect it. People trained for work at height should arrange safe access. A suitable specialist can assist on larger or more complex jobs. Inspection should go beyond checking the colour and signing the invoice.

Ask three specific questions. What support spacing does the documentation specify? How will air move through the roof? How will the chimney flashing be formed? The answers reveal more than a general assurance of quality.

Judge a roofer by their knowledge of the selected covering, the details of earlier jobs and how they organise the work. A clear scope and an inspection record help both parties. Settling responsibilities before ordering materials reduces grounds for dispute.