Sizes for every opening
Each window should be listed separately with its own width and height, not lumped into 'ten windows, various sizes'. Sizes should be taken from a survey, not the old advert measurements, because openings on older houses are rarely identical even when they look it from the street.
It's also worth checking that the quote names each opening by room, kitchen, front bedroom, landing and so on, rather than just a number. That way, when the order is confirmed, you're checking the same list rather than trying to remember which line was which.
Profile and colour
The quote should name the frame material (uPVC, aluminium) and the chamber count of the profile, plus the exact colour and finish, foil or spray, both sides if they differ. 'White windows' isn't a spec; 'white internal, anthracite grey foil external' is.
Chamber count matters because it affects both insulation and rigidity. A profile with more internal chambers traps more still air and needs less steel reinforcement to stay stable in larger sashes, so it's a fair thing to ask about rather than assume.
Glass spec and U-value
Look for the glass makeup written out: double or triple glazed, the cavity width, argon fill, warm edge spacer and low-E coating. The whole window's U-value (not just the glass) should be stated, along with its Window Energy Rating band where relevant.
The whole window U-value matters more than the glass on its own, because it accounts for the frame and spacer performance too. Two quotes both offering 'A rated glass' can still end up with different real world performance once the frame is factored in.
| Spec line | What it should say |
|---|---|
| Glazing | Double or triple, cavity in mm, argon filled |
| Spacer bar | Warm edge (not aluminium) |
| Coating | Low-E, and which pane it's on |
| Whole window U-value | A number in W/m squared K, not just 'A rated' |
Opener positions and locks
Which sashes are fixed and which open, and how (top hung, side hung, tilt and turn) should be marked, ideally on a small drawing. Locking hardware should name the type, an espagnolette or multi point lock, and any escape requirements for upstairs rooms.
Upstairs bedroom windows in particular often need to open wide enough and easily enough to act as a fire escape, so it's worth confirming this is accounted for rather than discovering it afterwards.
Trickle vents, disposal and making good
Building Regulations Part F generally require trickle vents when windows are replaced, so the quote should state whether they're included or why they're not needed. Disposal of the old frames and making good of the reveal, plaster or render should be named as included, not assumed.
- Trickle vents included, or a stated reason they're not required
- Removal and disposal of old frames and glass
- Making good internally around the reveal
- Making good externally where render or brick has been disturbed
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Certificate, guarantee and payment terms
You should be told how compliance will be certified (a FENSA style certificate or Building Control sign off), what guarantee covers the frames, the glass units and the fitting labour separately, and the payment schedule: deposit size, balance timing and how you're protected if the job stalls.
It's fair to ask for guarantee lengths for each of those three elements separately, since a long frame guarantee doesn't automatically mean the fitting labour carries the same cover.
It also helps to ask what happens if a problem shows up just outside a guarantee period, some companies will still take a reasonable view on a borderline case, and it costs nothing to ask that question before you sign rather than after something goes wrong.
Survey quote versus on the spot quote
There's a real difference between a quote given after someone has actually measured your openings and one worked out from a quick look round or from photographs sent over. A survey based quote can name exact sizes, confirm access for the fitting team and flag anything unusual, like a lintel that needs checking or an old frame that's been packed out with timber over the years.
An on the spot figure given at the first visit is often described as an estimate rather than a firm quote, even if it's presented confidently. It's worth asking directly which one you're being given, because the two carry very different weight if the final bill ends up different from what was first mentioned.
Common red flags on a quote sheet
A handful of patterns tend to repeat on weaker quotes, and spotting them early saves an awkward conversation later. None of these are automatically dishonest on their own, but two or three together are worth querying before you commit.
- A single total with no breakdown of sizes, spec or labour
- Vague wording like 'A rated glass' with no whole window U-value stated
- No mention of trickle vents either way
- Guarantee mentioned verbally but not written into the document
- Deposit terms missing or described only as 'usual terms'
What a thin quote leaves out
A quote that only shows a total price, a generic product photo and a deposit amount is not giving you enough to compare against another company or to hold anyone to later. If any of the lines above are missing, ask for them in writing before agreeing to anything, even informally.
It also helps to keep a copy of every version of a quote you're sent, including earlier drafts, since a later revision that quietly drops a line, such as making good externally, is far easier to spot when you can put the two side by side.