How to Start and Grow a Window Fitting Business in the UK

Window fitting is a high-value trade with strong underlying demand. Every house needs windows, and every window eventually needs replacing. In the UK, the combination of ageing uPVC window stock installed in the 1990s and early 2000s, rising energy costs driving homeowners to upgrade to double or triple glazing, and a thriving domestic extension and renovation market means that a well-run window fitting business has no shortage of enquiries. This guide covers everything from FENSA registration and setting up your supply chain to building a quoting process that wins jobs at the right margin.

FENSA Registration: Why It Matters and How to Get It

In England and Wales, any company that installs replacement windows or doors in a domestic property must either apply to the local authority for building regulations approval for each job, or use a competent person scheme to self-certify the work. FENSA — the Fenestration Self-Assessment Scheme — is the dominant scheme for window and door replacement, used by the majority of installers. CERTASS is the main alternative, offering similar self-certification rights with a slightly different assessment process.

In Scotland, the equivalent route is through Building Standards and the relevant local authority. BuildZone operates a similar scheme for Scottish installers.

FENSA registration matters commercially as well as legally. Homeowners are increasingly aware that a FENSA certificate is required to demonstrate compliance when selling their property. Estate agents and conveyancers routinely request FENSA certificates for windows installed after 2002. Installers who are not registered must warn customers that they will need to apply for building control approval at an additional cost — a significant competitive disadvantage. FENSA registration costs from around £600–£900 per year for smaller businesses, including an initial assessment and annual registration fee.

Services to Offer

Window fitters who expand their service range significantly increase their revenue per customer. The core services to build around are:

• uPVC casement and tilt-and-turn windows — the volume bread-and-butter of domestic window replacement. Fast to fit, strong margin when you have efficient supply.
• Sash window restoration and replacement — timber sash windows in period properties require specialist skills. Less competition, higher prices, and clients who are more loyal once they find someone they trust.
• Bi-fold and sliding patio doors — premium products with significantly higher ticket values. A single set of bi-folds can generate more revenue than four casement window replacements.
• Roof lanterns and flat rooflights — extensions and kitchen rear extensions increasingly feature large glazed roof elements. High value, less price sensitivity.
• Conservatories — full conservatory design and installation. Higher complexity, higher revenue, requires stronger project management capability.
• Composite and aluminium doors — front and back door replacement is a natural add-on to window jobs. Separate pricing, short install time, strong margin.

Pricing Guide

Window fitting pricing depends heavily on product specification, frame type, glazing unit specification, and the complexity of the existing opening. As a guide:

• uPVC casement window, standard size, supply and fit: £300–£700. Double glazing is standard; triple glazing commands a 25–40% premium.
• Aluminium casement window, supply and fit: £500–£1,200 per window depending on size and specification.
• Timber sash window, full replacement: £900–£2,500+ per window. Restoration of existing sashes: £400–£800 per window.
• uPVC bi-fold doors, 3-panel set: £1,500–£2,800. Aluminium bi-folds, same configuration: £2,500–£5,000+.
• Roof lantern, standard 1.5m x 2m: £2,500–£5,000 supply and fit. Larger bespoke sizes can exceed £10,000.
• Conservatory, uPVC frame with polycarbonate or glass roof: £8,000–£18,000. Full glass conservatory or orangery: £18,000–£30,000+.

Materials typically represent 40–55% of the total quoted price on standard uPVC work. Premium aluminium products can push materials higher. Labour is the remainder, minus overheads. A two-man crew fitting four standard casement windows per day at an average ticket of £450 each generates £1,800 in revenue — with material costs of around £800–£900, leaving a healthy contribution before van and overhead costs.

Choosing a Supply Chain

Your fabricator relationship is one of the most important decisions you make as a window fitter. The main options are:

• Local fabricators — regional manufacturers who make frames to your measurements and deliver within 7–15 days. Best for most small businesses. Building a strong relationship with one or two local fabricators gives you priority lead times and credit terms.
• National fabricators — larger operations like Eurocell, Deceuninck trade partners, or VEKA-approved fabricators. Often more consistent quality but less flexibility on lead times and minimum order sizes.
• Composite door specialists — companies like Solidor, Rockdoor and Hurst supply through trade networks. A trade account unlocks pricing that makes your margins workable.
• Aluminium systems suppliers — Schuco, Smart, and Senior Architectural Systems all have trade networks. Aluminium products typically require working with certified fabricators who hold the system manufacturer's approval.

Generating Leads

Window fitting is a high-intent, high-ticket purchase. Customers do not impulse-buy new windows — they research, get multiple quotes, and then decide. Your marketing needs to be present at both the research stage and the decision stage:

• Google Local Services Ads — the highest-intent channel for window replacement searches. 'window fitters near me' and 'replace windows [city]' searches convert strongly. Google Guaranteed status (part of LSA setup) builds trust with wary homeowners.
• Checkatrade and Rated People — directories remain effective for homeowners validating local tradespeople. Your review count and average rating directly affect enquiry volume.
• Referrals — satisfied window customers are highly likely to recommend. Systematically asking for referrals after every completed job, offering a small discount voucher for both referrer and new customer, costs almost nothing.
• Estate agents — rental property landlords frequently need to upgrade windows to meet EPC targets or letting standards. Estate agents managing large rental portfolios are an underused referral source.
• Builders and extensions contractors — builders doing rear extensions need a reliable window supplier for the new glazed openings. A referral relationship with two or three local builders can generate consistent work.

The Quote Process: Survey to Signed Contract

Window fitting quotes cannot be given accurately over the phone. Every job requires a site survey to measure the openings, assess the reveal depth, check the lintel, and identify any complications (bay windows, lead flashing, shaped frames). A professional quote process builds confidence with the customer and protects your margin:

• Site survey — visit within 2–3 business days of the enquiry. Customers who get a fast survey response are significantly more likely to choose you. Measure every opening, photograph each window, note any complications.
• Measured quote — produce a written quote within 24 hours of the survey. Include a clear product specification, energy rating, guarantee terms, and FENSA registration details. Itemise each window and door separately.
• Deposit and sign-off — a 25–35% deposit is standard for bespoke manufactured products. Use digital sign-off so customers can approve the quote and pay the deposit online, without back-and-forth.
• Installation — schedule the install date when the deposit is received. Confirm the week before and the day before. Arrive on time, protect the property, and clean up fully on completion.
• FENSA certificate — register the installation with FENSA within the required period and provide the certificate to the customer. This is what they need for their property sale records.

Profit Margins and Financial Planning

Window fitting businesses that grow sustainably share a common discipline: they know their numbers. The most important metrics to track monthly are:

• Average job value — aim to increase this over time by adding premium products and upselling conservatories and bi-folds alongside standard window replacements.
• Quote conversion rate — tracking how many surveys convert to signed jobs tells you whether your pricing is competitive and your presentation is effective. A 40–60% conversion rate is healthy.
• Material cost as a percentage of revenue — if this creeps above 55% on standard uPVC work, your fabricator pricing needs renegotiating or you need to review your quotes.
• Revenue per fitting day — a productive two-man crew should generate £1,500–£2,500 in revenue per day on standard work. If it falls below this, look at scheduling efficiency and job mix.

How Trade2Base Helps Window Fitters

Trade2Base is designed around the job lifecycle that window fitters run every week — from initial enquiry through survey, quote, deposit, installation, and certificate to the Google review:

• Quote builder with digital sign-off — build itemised window-by-window quotes and send them to customers for digital approval. Customers sign and pay the deposit online, without printing or posting anything.
• FENSA certificate storage — store the FENSA certificate and job documentation against each customer record. Customers can access their certificates through the portal at any time.
• WhatsApp communication — confirm surveys, installation dates, and job updates via WhatsApp directly from the platform. Customers love it; no-shows drop significantly.
• Stripe deposit payments — collect your 25–35% deposit by card online when the customer approves the quote. No more chasing or waiting for bank transfers.
• Customer portal — give customers a dedicated portal where they can view their quote, sign off, pay, and access their FENSA certificate and job photos.
• Google review automation — send an automated review request after every completed installation. Consistently collecting reviews is the highest-ROI marketing activity a window fitter can do.
• Campaign attribution — know whether your Google Ads, Checkatrade, or referral programme is generating the most booked jobs. Stop guessing and start spending on what works.