Which measurements are needed for made-to-measure chimney flashings?

Each side should have its own dimensions. It is not worth assuming a perfectly rectangular outline without checking. Chimney cladding or uneven workmanship may change the actual shape. Measurements should be taken safely, entrusting roof access to a person prepared for such work.

The flashing must fit what will remain on the building after the work is completed. If the chimney is to receive additional cladding, it must be included in the dimensions. Measuring the core alone may be insufficient. It is also important to establish which material the seal will connect to.

Visible offsets, projections and changes in cross-section should be noted. They may affect the upper termination of the chimney flashing. It is worth attaching photographs of each side together with a clear sketch. Photographs help to understand the situation but do not replace numerical values.

The roof pitch affects the shape of the side parts and the course of the joint. Information about it should reach the flashing installer. The type and profile of the covering are also needed. The detail for tile-effect metal roofing may differ from the solution used for a specific sandwich panel.

It is worth indicating the position of the chimney relative to the ridge, eaves and roof valley. Adjacent elements may restrict space or change the path of water. The penetration should not be analysed in isolation from the roof. In particular, the part located above the chimney requires a clear plan for drainage.

The quote may cover just the bent strips or a set prepared for a specific solution. The scope must be clearly defined. It is worth separating chimney flashings from seals, fixings and installation work. This allows quotes to be compared without guessing at missing items.

It should also be checked which adjustments will be made in the workshop and which on site. This applies to corner joints and the ends of individual parts. If unusual flashings are required, they should have their own drawings. The general term chimney set does not describe their geometry.

Galvanised, aluzinc and coated steel sheets have different specifications. A specific version suited to the conditions of use must be selected for the order. For coloured surfaces, the colour and finish are specified. The material should be compatible with adjacent roof components.

The visible side is marked on the cross-section. With asymmetric flashings, incorrect orientation of the colour can prevent correct installation. The appearance should be coordinated with ridge tiles, verge flashings and gutter aprons. This is not, however, a reason to omit the requirements specific to the chimney zone.

The sheet metal collar is used to resolve the junction with the covering. It does not replace the structural documentation or the requirements for the chimney. When quoting, it should not be expected that the shape of the sheet alone will settle all these matters. The relevant data should be established before ordering.

For sandwich panels, a solution for their terminations at the opening is also required. Wall starter profiles do not share a function with this detail, although they may be included in the same delivery. Each cladding component should have a defined purpose. Organising the scopes makes later acceptance of the works easier.

Before production, the order drawing should be compared with the measurements. Particular attention must be paid to the description of sides and the angles. If the contractor makes a correction, the document must be updated. Two different sketches of the same chimney should not be valid at the same time.

After delivery, completeness and the sheet surfaces are checked. The chimney flashings should be trial-fitted in the agreed installation sequence. A major discrepancy should not be corrected by randomly stretching or bending components. First it must be established whether the problem lies in the measurement, the production or a change made on the building.