The short answer
Ask for glass, frames, sills and doors to be listed individually. Identify the finish and any specialist marks before a cleaner chooses products; a window-cleaning quote does not automatically include every uPVC surface.
List the parts you mean
External glass is one element of a window assembly. Frames, sills, doors, glazed panels and decorative trim may require a different scope. State whether you want external surfaces only and include photographs of the parts that matter. Gutters, fascias and soffits are separate exterior features and should be named if you want them priced as well.
Identify the finish and the problem
Tell the provider about coloured or foil-wrapped finishes, painted areas and any manufacturer information you hold. Include close-ups of discolouration, adhesive, paint spots or other residues. A white appearance alone does not establish the material or a suitable cleaning product. Ask for existing damage to be recorded and for the limits of stain removal to be explained before booking.
Keep routine cleaning and restoration distinct
Removing ordinary surface dirt is a different proposal from attempting to restore a changed finish or remove building residue. Ask whether a trial is needed and what result it is intended to establish. Do not assume stronger chemicals or abrasive work are included in a routine price. The provider should check the product’s care guidance and explain the proposed approach for your actual windows.
Check the completion scope
Use your original parts list when the clean is finished. If the quote includes frames and sills, check those alongside the glass. Ask what aftercare or drying period applies to any specialist work. Discuss remaining marks in WhatsApp with a clear photograph and the agreed scope, rather than comparing the result to a different service that was never included.