How to start a window fitting business in the UK

Is window fitting a good trade to get into?

Window fitting sits in a sweet spot in the UK building trades. Demand is steady — driven by the government's push to improve home energy efficiency, the steady turnover of ageing double-glazing units from the 1990s and 2000s, and new-build completions running at around 230,000 homes a year. It is not a trade that disappears when the economy softens, because replacing failed sealed units or broken frames is maintenance, not luxury.

The average window fitter in the UK earns between £28,000 and £45,000 a year as an employee. Running your own business, a sole trader with low overheads can generate £40,000 to £70,000 in turnover with the right client base, and more if you move into conservatories, bi-fold doors, or commercial work.

Qualifications and certification

There is no single mandatory licence to fit windows in the UK, but two things matter enormously for trading legally and commercially:

FENSA or CERTASS registration

Under the Building Regulations (Part L for England and Wales), replacing windows and doors is controlled work — it must comply with minimum thermal performance standards. As a FENSA or CERTASS-registered installer, you can self-certify your work and issue compliance certificates directly to customers. Without this, each job requires a Building Control application, which takes time, costs money, and puts customers off.

FENSA registration costs around £200 to £400 a year depending on your turnover. Apply at fensa.org.uk. CERTASS is an alternative with similar cost and benefits.

Glass and glazing qualifications

An NVQ Level 2 or 3 in Fenestration Installation gives you recognised credentials and is required by some larger contracts. City and Guilds and NOCN both offer relevant qualifications. If you want to work in social housing or commercial contracts, formal qualifications significantly improve your chances.

Tools and equipment

Starting out, the core kit for a window fitter includes a cordless combi drill and impact driver, an angle grinder for cutting sill extensions, an oscillating multi-tool for removing old frames, spirit levels (600mm and 1200mm), silicone guns, plastic packers in mixed sizes, tape measures, squares, and marking tools. Budget around £1,500 to £3,000 for a solid set of hand and power tools. A van is essential — most window fitters use a medium wheelbase Transit or similar with good racking to protect frames during transport.

How to price window fitting jobs

Pricing varies depending on the frame material, the job size, and your region. Rough 2026 benchmarks: a standard uPVC casement window supply and fit costs £400 to £700. A uPVC bay window (3 pane) runs £1,200 to £2,000. Aluminium casements are £600 to £1,100. A front door replacement is £800 to £1,800. Failed sealed unit only work comes in at £80 to £180.

If you are fitting customer-supplied frames, labour-only rates typically run £80 to £150 per window depending on complexity. Use the free quote generator to produce professional quotes for customers — it makes a real difference to conversion rates.

Insurance for window fitters

You need at minimum: public liability insurance at £2 million cover minimum (around £200 to £400 per year for a sole trader); employers liability insurance, legally required the moment you take on any staff or labour-only subcontractors; tools and equipment insurance; and contract works insurance to cover materials and work in progress if a job is damaged before completion. See our guide on tool theft insurance for tradespeople for more on protecting your tools.

Finding your first customers

Word of mouth is the biggest source of work for window fitters, but you need a base to build from. Set up a Google Business Profile and ask every customer for a review — five genuine reviews puts you ahead of many competitors. Register on Checkatrade, TrustATrader, or MyBuilder to get leads while building your own reputation. Leaflet drops in residential areas are still effective for local trades. Partner with local estate agents and letting agents for window replacements on rental properties, and contact local builders who need windows fitted on refurbs. For more strategies, see our guide on winning more quotes as a tradesperson.

Invoicing and VAT for window fitters

You must register for VAT once your taxable turnover exceeds £90,000 in a 12-month period (2026 threshold). Window fitting supplied and fitted to residential customers is standard-rated at 20% VAT. Some energy-saving work may qualify for a reduced rate — check the HMRC guidance on VAT for energy-saving materials. Use InvoiceAdept to invoice customers professionally, track payments, and keep MTD-ready records automatically.