Planning a roof replacement: what to check and in what order

The inspection should cover the covering, roof structure, supports and connections. It must be established whether the leak results from material wear or from an error at the chimney, roof valley or eaves. If the cause lies in a detail, replacing the sheets alone may not remove it. It is also worth inspecting the loft after rain and noting signs of moisture and deflection.

An old roof can hide damage to the timber and layers that cannot be assessed without exposing them. The cost estimate must provide for how to proceed once they are revealed. This does not mean extending the works arbitrarily without agreement. It is better to define in advance who assesses the condition and how additional works are documented. This protects the schedule and allows the budget to be controlled consciously.

The new covering must suit the pitch and the method of support. Lightweight steel sheet can reduce the dead load compared with a former heavier material. Snow, wind and the new layers added during the renovation must still be checked. A change in batten spacing and eaves position can affect gutters and flashings. The replacement should not be treated as a simple change of colour.

On a simple roof slope, sheets cut to length can be considered. Modules are often more convenient where access is difficult or there are more offcuts. T18 and T35 are worth comparing on buildings of simpler form. In every case a cutting plan based on measurement of the roof is needed. Dimensions from an old design may not reflect the actual geometry.

The material and the most important accessories should be available in line with the schedule. Unloading, storage and safe protection of the building against precipitation must be established. The extent of roof exposure should match the team’s capacity and the weather conditions. A casually stretched tarpaulin will not always protect the interior in strong wind and prolonged rain.

It is worth protecting the rooms and the surroundings of the building from falling waste. Removed material should be directed to the appropriate form of disposal. If the old covering may contain asbestos, identification and a specialist procedure are required. It should not be broken or cut by hand. This stage must be established before ordinary roofing works begin.

The exposed roof slope allows the substrate and details at penetrations to be repaired. An improvement in thermal insulation can also be analysed. A continuous PIR layer above the rafters is often useful when thermal bridges need to be reduced and space inside preserved. However, it requires a solution for fixings and changes in height at the eaves, ridge and windows.

It is not worth adding insulation without checking for moisture and airtightness from the interior. Wet layers must first be diagnosed. New roofing can seal off the existing drying path. Therefore, the renovation should include a coherent assembly of building layers. Simply increasing insulation thickness will not eliminate draughts or leaky joints.

Accept each stage before it is covered. Check the structural repairs, the substrate, the eaves and the flashings at penetrations. Photos help later to establish what was actually done. Changes to the scope should be described and priced. It is worth separating work that becomes necessary after damage is discovered from additions arising from a new aesthetic decision.

The cost can increase due to insufficiently calculated accessories, transport and access to the roof slope. Therefore, the first quote should cover the complete scope. It is also worth establishing whether the contractor replaces the gutters and safety elements. Leaving worn fasteners or leaky drainage with new sheet metal can quickly worsen the result of the entire renovation.

Check the condition of the coating, the sheet joints, the flashings and the patency of the drainage. No filings, cuttings or transport film should remain on the roof. Ventilation must maintain the planned flow path. It is worth inspecting the attic after the first rainfall. Such a review helps to catch a minor problem before it leads to damage to the interior finish.

Keep the material list, the instructions and the photographic documentation. Establish maintenance rules and service access. A well-executed replacement should solve the causes of the old roof’s wear, not just improve its appearance. The greatest benefit comes from combining correct roofing with structural repair, airtight layers and efficient water drainage.