Choosing the right sash window company matters more than almost any other decision in the project. A good specialist will advise you honestly on repair or replacement, deal with planning rules and do work that lasts for decades. These 12 questions will help you compare firms and spot the ones to avoid.
12 questions to ask
- Do you specialise in sash windows? General window firms often focus on uPVC casements. A sash specialist understands box frames, weights and period details.
- Do you repair as well as replace? A firm that only sells new windows may not tell you when restoration would be cheaper.
- Can I see examples of similar work, and speak to past customers? Ask for photos and references for homes like yours.
- Do you make the windows yourselves? Firms with their own workshop can match details exactly; others buy in. Both can be good, but you should know which.
- What timber, glass and paint system will you use? Compare like with like. See our timber sash windows guide.
- Weights and pulleys or spiral balances? See sash window weights vs spiral balances.
- Have you worked in conservation areas or on listed buildings? If your home is in one, you need someone who knows what councils approve. See our guides to conservation areas and listed building windows.
- Will you help with planning or listed building consent? Good firms supply drawings and advice.
- Can you self-certify under building regulations? For replacement windows, ask whether they are registered with a scheme such as FENSA or CERTASS, so you get a compliance certificate.
- What insurance do you have? Ask about public liability insurance as a minimum.
- What guarantees do you give? Ask separately about the timber, glass, paint finish and workmanship, and whether a deposit or insurance-backed guarantee protects you.
- How long will the work take, and how will you protect my home? Ask how many windows are done each day and whether openings are secured each night.
Red flags
- Pressure to sign on the day, or “today only” discounts
- A large deposit demanded up front
- No written quote, or a single price with no breakdown
- Recommending replacement without inspecting the timber
- Vague answers about planning rules
- No address, no reviews or no verifiable past work
How to compare quotes
Get at least three written quotes and check that each covers the same things:
| Check | Why it matters |
|---|---|
| Price per window, broken down by job | Lets you compare fairly and spot padding |
| Timber species and glass specification | The biggest drivers of quality and price |
| Draught-proofing included? | Often an extra |
| Painting and number of coats | Affects how long the finish lasts |
| Making good, disposal and access | Hidden extras on many quotes |
| Guarantees and payment terms | Protects you if something goes wrong |
Use our price guides to check the numbers: sash window repair costs, sash window replacement cost and double glazed sash windows: costs and options.
Speak their language
Knowing the names of the parts helps you describe problems and understand quotes. Keep our sash window parts glossary to hand.
Find a specialist
SashWindow.co lists sash window companies by area, with the services and products each one offers. Find sash window companies near you or browse by area, then use the questions above to choose.
Frequently asked questions
How do I find a good sash window company?
Look for a firm that specialises in sash windows, offers repair as well as replacement, can show similar past work and gives a detailed written quote with clear guarantees.
How many quotes should I get for sash windows?
At least three. Make sure each covers the same specification so you can compare fairly.
Should a sash window company be FENSA registered?
For replacement windows, choose a firm registered with a competent person scheme such as FENSA or CERTASS so it can self-certify building regulations compliance. Repairs do not usually need this.
What deposit should I pay for new sash windows?
Avoid paying a large deposit up front. Ask how your deposit is protected, and pay the balance only when the work is complete and you are happy.
Plain-English guides to repairing, draught-proofing and replacing period sash windows, from the SashWindow.co team.
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