Installation · 8 min read
How to Compare Window Quotations
Two quotations for the same project can differ by thousands and both be honest — because they are rarely quoting the same thing.
Why Are Window Quotes So Different?
Because they are usually quoting different things. Most of the variation is system, glass specification and how much of the work is actually included.
3 min read
Written by Windows in the Lakes · A trading name of Home Glazing Ltd · Last reviewed 21 September 2026
Short answer
In short: a spread of fifty per cent or more across three quotations is normal and rarely means anyone is being dishonest. It means the specifications are different. The way to compare them is to reduce each one to the same six facts, and then look at the price.
Reduce every quotation to these six facts
- 011. The systemThe exact system and profile range, not just the material. This alone explains much of the variation.
- 022. The glassUnit make-up, coatings, gas fill, spacer type and any acoustic or solar specification.
- 033. The hardwareHandle and hinge ranges, locking specification and any security accreditation.
- 044. The scope of installationRemoval, disposal, fixing, sealing, internal making good, external making good.
- 055. AccessWhether scaffolding or access equipment is included or excluded.
- 066. Certification and guaranteeHow Building Regulations compliance is handled, what is guaranteed, for how long and by whom.
Where variation hides
| Line | Cheap quotation often assumes | Realistic quotation states |
|---|---|---|
| Making good | Excluded, or 'by others' | Internal reveals and external seals included, with the standard described |
| Access | Ladder access throughout | Scaffolding or access equipment priced where the elevation requires it |
| Disposal | Left on site | Removed and disposed of |
| Glass | Standard unit throughout | Specified per elevation, including safety glass where required |
| Trickle ventilation | Not mentioned | Addressed, because current regulations frequently require it on replacement |
| Lead time | 'A few weeks' | A stated manufacturing period from confirmed survey |
When a lower price is entirely legitimate
Lower prices are not automatically suspicious. A smaller business with lower overheads, a supplier with a particularly efficient relationship with one manufacturer, or a quieter period in the calendar can all produce a genuinely lower figure for identical work. The test is whether the scope matches, not whether the number is low.
Sources and further reading
Regulatory and technical points in this guide should be checked against the current published guidance below, and against the specific circumstances of your property.
Guidance last reviewed 21 September 2026 by Windows in the Lakes
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