How to Become a Window Fitter in the UK (2026 Guide)

Window fitters remove old windows and doors and install replacements. Day-to-day work includes:

• Surveying and measuring — precise measurements for manufacturing new windows and doors
• Removing old frames — carefully extracting existing windows, managing waste disposal
• Preparing openings — ensuring reveals are clean, level, and structurally sound
• Installing new frames — positioning, levelling, and fixing new window and door frames using mechanical fixings
• Sealing and weatherproofing — expanding foam, silicone sealant, and weather membranes
• Glazing — installing sealed glass units into frames (double or triple glazing)
• Finishing — fitting trims, sills, cills, and internal/external finishing
• Door installation — composite, uPVC, aluminium, and bifold door fitting
• Bifold and sliding doors — high-value specialist work with growing demand
• Building regulations compliance — ensuring installations meet thermal performance (Part L) and safety standards

Most domestic window work involves uPVC replacements, but the market for aluminium (modern/architectural), timber (heritage), and composite frames is growing. Commercial work includes curtain walling, shopfronts, and fire-rated glazing.

Route 1: On-the-Job Training (Most Common)

1. Start as a labourer/mate with a window company — carry frames, remove old windows, clean up. No qualifications needed to begin.
2. Learn from experienced fitters (6-12 months) — progress to fitting under supervision. Learn measuring, frame fixing, and sealing techniques.
3. Develop independence (12-18 months) — start fitting standard windows independently. Build speed and accuracy.
4. Complete NVQ Level 2 in Fenestration Installation — assessed on-site while working. This is the formal qualification for window fitters.
5. Get FENSA registered (if self-employed) — to self-certify that installations comply with building regulations.

Route 2: Apprenticeship

A Level 2 Apprenticeship in Fenestration Installation takes 12-18 months. Combines on-site work with training.

Important: FENSA Registration

FENSA allows registered installers to self-certify that window replacements comply with building regulations. Without FENSA (or equivalent — CERTASS, etc.), every installation needs separate building control approval. Self-employed window fitters should be FENSA registered.

Day 1 of a 2-day whole-house window replacement:

7:30 AM — Load the van with pre-manufactured windows (8 windows + 1 composite front door for a 3-bed semi). Check all frames against the order.

8:00 AM — Arrive at the customer's home. Walk through the plan.

8:30 AM — Start with the front bay window. Carefully remove the old timber frames — this house has original 1970s single-glazed windows. Clean the reveals, check for damage.

9:30 AM — Install the new uPVC bay window. Position frames, check for level and plumb, fix with frame fixings. Expanding foam, external sealant.

10:30 AM — Install glass units into the bay. Each sealed double-glazed unit is heavy (30-40kg). Bead the glass, check operation of opening sashes.

11:30 AM — Move to the two front bedroom windows. Standard casements — faster to fit. One hour each.

1:00 PM — Lunch.

1:30 PM — Afternoon: rear kitchen window, dining room window, and bathroom window. The bathroom is obscure glass.

4:00 PM — Install internal trims around completed windows.

4:30 PM — Clean up, remove old frames for disposal.

Tomorrow: remaining windows, composite front door, and all finishing.

This job earnings: 8 windows + 1 door, 2 days. Fitting price: £1,600-£2,200. That's £800-£1,100/day for a two-person team.

Employed Window Fitter:
• Trainee/labourer: £20,000-£24,000
• Qualified fitter: £26,000-£35,000
• Experienced fitter: £32,000-£40,000
• Surveyor/estimator: £30,000-£42,000

Self-Employed Window Fitter:
• Starting out: £30,000-£38,000
• Established: £38,000-£55,000
• With own supply & fit business: £50,000-£80,000+ (business income)

Pricing structure:
• Standard window fitting (supply by company): £80-£150 per window
• Supply and fit (self-employed): £300-£600 per window to customer
• Composite door fitting: £150-£300 fitting only
• Bifold door installation: £400-£800 fitting only

*Sources: ONS, Glassdoor, FENSA, GGF, and industry data.*

Key earnings insight: The real money in window fitting is supply-and-fit. Self-employed fitters who source windows directly from manufacturers at trade prices and sell the complete package earn significantly more than fitters who just charge a fitting rate.