With a large order, flashings often come from several batches or arrive on site at different times. It is then easy to mix up the material, the surface finish or the colour side. One clear schedule limits the problem. It should describe each group of elements, from ridge caps to starter profiles. A joint delivery makes sense when all parts are easily identifiable and correspond to the approved specification. Ridge caps, barge flashings, gutter aprons and chimney flashings should be listed in separate rows. For each, add the cross-section, length and number of pieces. Starter profiles and other plinth elements should also be separated. This allows quantities to be checked without mixing the functions of similar profiles.

Follow the water from the glazing, down the frame and across the sill when choosing an external window sill. A suitable outward fall, a drip edge clear of the façade and a sound junction with the window matter more to durability than the colour or finish. Select the coating once these details have been settled. On a refurbishment, lift the old sill and inspect what supported it. An uneven or poorly formed base may let water reach the wall long before a stain appears on the visible surface.

With a parapet, the building perimeter is not the only thing that matters. Copings must fit the actual wall width, the position of the layers and the planned drainage. The order must include straight sections, corners and changes in height. A complete set prepared in this way is easier to install and to accept. It also avoids a situation where the straight strips are ready but one end piece is missing, stopping the whole parapet from being closed. Measurement should cover all layers that will sit under the flashing. The dimension of the wall or structure alone is not enough. The final finish on both sides must be taken into account. If the façade is not yet finished, its actual thickness needs to be agreed.