Choosing a roofing contractor: how to assess the quotation

First prepare a description of the roof. You need its dimensions, shape, the type of covering planned and the number of chimneys and windows. For a renovation, add photos of the loft and information about leaks. On this basis the contractor can assess the scale of the task. A quote based solely on a photo of the elevation should be treated as preliminary.

Choose a team that works with the given system. Experience in laying roof tiles does not yet confirm familiarity with the joints of modular tile-effect metal roofing or an insulated sandwich roof panel. Ask who will manage the works and who will check the first part of the installation. The person selling the service does not always work on site later.

Ask for examples of roofs similar to yours. More important than a photo of the whole building are shots of the roof valleys, chimneys, eaves and ridge. These places show how water is directed and how the sheet metal is finished. A simple roof slope can look good even when the most difficult joints have been done carelessly.

If the owner of an earlier project agrees to talk, ask about how the acceptance went and how the team responded to the comments raised. Looking at a roof that is several years old gives different information than a photo from the day of installation. Do not expect, however, that sight alone will replace a technical assessment. Some defects remain hidden.

Compare dismantling, substrate preparation, laying of the covering, flashings, drainage and transport separately. Check whether scaffolding, protection of the building against rain and removal of waste are included in the price. An amount per square metre of roof slope without these items cannot be compared with a quote covering the whole scope.

The materials list should include the sheet thickness, the type of coating and the necessary accessories. The term “graphite sheet metal” is not precise enough. Also establish whether the settlement relates to the covering area, the sheets purchased or the actual roof area. With many cuts, these quantities differ.

A good starting point is to ask about the installation instructions for the chosen covering. The contractor should be able to explain the choice of substrate, batten spacing, direction of laps and method of fixing. It is not a memory test. What matters is that they can point to the document from which the adopted solutions derive.

Also ask about ventilation under the metal sheet and drainage of water from the underlay. Sealant does not replace a correctly formed flashing. For a sandwich panel, different details are needed than for metal sheet on battens. These two technologies should not be priced or executed according to one scheme.

Record the scope of works, the deadline, the method of settling changes and the acceptance rules. Establish who is responsible for ordering sheet lengths and for assessing the old structure once exposed. If damaged timber is found, the decision to replace it should precede covering it up and additional billing.

It is worth linking the payment schedule to recognisable stages. Discuss the material warranty and responsibility for installation separately. These are different matters. Keep purchase documents, instructions and photos of the works. In the event of a later defect report, they will make it easier to reconstruct what was actually done.

Suppose one team quoted only for installing the covering, while the other also included new battens, gutters and flashings. The difference in the final amount then says nothing about the rate for the same service. Transfer the items into one table and ask for the gaps to be filled. Only such a scope allows a sensible conversation about costs.

Ask about items settled after the old roof is exposed. It is possible to set a rate for a specific type of additional work, the method of documenting it and the requirement for approval before execution. This reduces the risk of a dispute over a cost that neither party could reliably determine before dismantling.

Do not treat a fast deadline as a defect or a long queue as proof of quality. What matters more is a realistic work plan and the availability of a suitable team. When the quote does not specify details, ask for them to be added before payment. A reliable quote should be verifiable without guessing the contractor’s intentions.

Plan an inspection of the substrate and layers before the metal sheet is laid. Afterwards, check the continuity of flashings, the alignment of gutters, the fixing of accessories and the condition of the coating. No swarf or cuttings should remain on the surface. It is worth attaching photos of details to the report together with a list of defects and a deadline for their removal.

If the roof is complex or requires structural repairs, the help of an independent specialist may be more useful than another round of price negotiations. Acceptance should compare the execution with the design and the system instructions. A promise that ‘we always do it this way’ does not resolve a discrepancy in an important detail.