12 Questions to Ask a Window Company Before You Sign

Why it matters: material names are too broad. Different systems have different profiles, opening limits, thresholds, drainage, hardware and visual character. A good answer names the system, identifies the relevant configuration and explains why it suits the openings. Warning signs include an unnamed ‘premium aluminium’ or ‘heritage-style’ product that cannot be tied to a written specification.

Follow with question 2: What glass specification is included? A useful answer covers the build-up and any safety, solar-control, acoustic, privacy or thermal requirement relevant to each opening. Ask for whole-window performance where that is the issue, not only the centre-pane figure.

The survey converts the design and provisional dimensions into manufacturing information. Ask who attends, what they check, who owns the final sizes and how the survey is recorded. A good answer covers openings, levels, tolerances, finishes, cills, thresholds, access and interfaces — not simply width and height.

Ask what the installation figure covers from delivery to handover. Does it include setting and fixing frames, glazing, perimeter sealing, cills, thresholds, trims, protection and final adjustment? Who supplies access equipment or lifting equipment for large glass? A good answer defines both the included work and the boundary with the builder, plasterer, renderer or decorator.

Question 6 is separate: Is removal and disposal included? Removal can expose failed lintels, damaged reveals or hidden damp. The quotation should state whether old frames and waste leave the site, and how unforeseen building defects are treated.

‘Making good’ can mean a narrow sealant joint to one company and plaster, render, stone pointing, trims and decoration to another. Ask for the internal and external finish at each opening, including what will not be reinstated. A useful answer names the materials and stopping point. ‘As required’ is not a specification.

A candid exclusions list improves a quotation. Common exclusions include scaffolding, cranes or specialist lifting, structural steelwork, lintels, electrical work, alarms and sensors, blinds, decorating, flooring, asbestos work and repairs to concealed defects. None is automatically unreasonable; the risk lies in discovering them after comparing totals.

Ask which route applies to your work and who arranges it. Replacement windows may be self-certified by an appropriately registered installer or dealt with through Building Control. New-build glazing is normally part of the wider Building Regulations process. Planning permission, listed building consent and Article 4 controls are separate and should not be confused with certification.

Do not accept a logo as the whole answer. Ask whose registration covers the installation and what document you will receive. Windows in the Lakes does not itself claim competent-person-scheme registration; the applicable route and installation-team status are confirmed for the project.

Frames, finish, sealed glass units, hardware and installation may have different terms and providers. Ask for those terms in writing, including start date, exclusions, maintenance conditions and claim route. A long headline period is less useful than clear cover from an identifiable party.

Ask who receives the first call, how service work is triaged and what happens where responsibility sits with a manufacturer or another trade. Doors and opening windows may require adjustment after a building settles; a practical service process matters more than a vague promise that problems are ‘never an issue’.

Ask for projects relevant to your scale, property and product. A 5.6-metre slimline sliding door in a barn conversion near Brampton is useful evidence for large-glass handling and rural access. A 36-opening stone self-build in West Yorkshire is relevant to sequencing, measured manufacture and consistent detailing. Neither is a substitute for checking your own specification.

1. 01Which exact system?Name, profile, configuration and finish.
2. 02Which glass?Build-up and performance for each relevant opening.
3. 03Who surveys?The person, checks and record used for manufacture.
4. 04What if measurements change?The approval process for a revised scope or price.
5. 05What installation is included?From access and delivery through sealing and adjustment.
6. 06Are removal and disposal included?Including waste and treatment of concealed defects.
7. 07What making good is included?Internal and external materials and responsibility boundaries.
8. 08What is excluded?Access, structure, decoration and every provisional item.
9. 09How is certification handled?The route, responsible party and document supplied.
10. 10Which warranties apply?Provider, cover, term, conditions and claim route.
11. 11What happens after installation?Service, adjustment and escalation arrangements.
12. 12Can I see comparable work?Projects that genuinely resemble your brief.

Every question above is reasonable. We would rather clarify a system, exclusion or responsibility before order than rely on an assumption. For a Windows in the Lakes quotation, ask us to identify the products, glass, survey route, installation scope, experienced installation teams we know and trust, making-good boundary, certification route, written warranties and comparable work. If an answer depends on a final survey or another professional, we will say so.

Listen for specificity, ownership and written follow-through. A useful answer identifies the product or person, states where responsibility starts and ends, and can be reflected in the quotation or order. A weak answer relies on broad reassurance, changes depending on who is speaking or leaves an important item to be settled after manufacture.

There is no single correct commercial model. One company may use its own installation team; another may use experienced installation teams it knows and trusts. One may self-certify eligible replacement work through an appropriately registered installer; another may use Building Control. The question is whether the route is valid, disclosed and managed — not whether every supplier gives the same answer.

• Ask for technical answers to be reflected in the written specification
• Ask for commercial exclusions to appear beside the price
• Ask who has authority to agree a change after survey
• Keep approved drawings and finish samples with the order
• Do not sign while a material responsibility is described as ‘to be agreed’

The twelve questions establish a sound baseline. Your building will add others. On an exposed site, ask how the exact frame, drainage and perimeter detail have been selected for the elevation. On a stone property, ask where the frame will sit and how irregular reveals will be finished. On a self-build, ask when openings can be released for manufacture and who owns their tolerances.

For large sliding or bifolding doors, confirm panel sizes, sightlines, threshold, drainage, glass handling and structural support. For a listed building or conservation area, ask which details need approval and who will supply drawings or samples. These questions do not make the purchase cumbersome; they expose decisions that the project already contains.