Your First Year as a Window Fitter: What to Expect

‍‌​​​​​‌​​‌​‌‌‌‌‌​‌‌‌​‌‌​​‌​​‌​‌​‍Window fitting is one of those trades that looks simple until you realise you're dealing with Building Regs, thermal performance standards, glazing safety law, and customers who'll call you back about every drop of condensation.

The improver reality

Most people starting in window fitting aren't ready to run installs solo on day one. That's normal - you're an improver. Own it. Don't pretend you know every frame type and fixing method when you've only been on the tools a few months. Watch experienced fitters, ask questions about surveying, packing, and sealing, and learn why they do things a certain way - not just how. The good ones will teach you if you show willing. This stage lasts months, sometimes a year. It's not a failure - it's how every competent window fitter starts.

1. Reality check: your first year

First year, you're mostly a mate/installer on PVC and aluminium windows and doors, not running your own FENSA-approved firm just yet. You'll be:

• Measuring and helping order jobs.
• Ripping out old frames without wrecking reveals.
• Fitting new units, packing, fixing, sealing and trimming so they're weathertight and safe.

It's physical and picky work, but demand is steady: every house has windows, and current Part L changes mean replacement windows have to hit tighter U-values than before, so customers are still spending on upgrades.

2. Cards, NVQs and competent person schemes

GQA Level 2 NVQ in Fenestration Installation

This is the standard qualification for fitters.

Mandatory units cover:

• Health, safety and welfare.
• Communicating and working with others.
• Locating, transporting, handling and positioning materials.
• Identifying and confirming installation requirements.

Optional units cover the actual fitting tasks:

• Prepare and shape products, prepare the site and tools.
• Remove existing windows and doors and prepare apertures.
• Prepare and position units, install glass/panels, seal and finish.

Some providers advertise fast completion in 4-8 weeks for experienced fitters via on-site assessment. Costs are typically £800-£1,500 depending on provider and assessment method.

FENSA and CERTASS -- self-certifying Building Regs

As a fitter going self-employed, you either join a competent person scheme (CPS) or pay Building Control each time.

• FENSA is the best-known CPS for replacement windows and doors in existing homes.
• CERTASS is an alternative CPS for window and door installers.

As an approved FENSA/CERTASS installer, you can self-certify your own installations to current Building Regulations as an alternative to using Building Control.

Important: FENSA/CERTASS are for the business, not the individual -- you join once you're up to scratch with Part L/K and have enough jobs under your belt.

FENSA/CERTASS costs

Budget for these before you register:

• FENSA: annual registration fee (typically £300-£500+ depending on business size) plus a per-job notification fee (typically £30-£40 per installation notified).
• CERTASS: similar structure with annual and per-job fees.
• These are business costs that eat into your margin if you don't price for them.

3. Building Regulations and standards

Part L -- thermal performance

Recent changes tightened the rules for replacement windows:

• For existing dwellings in England, updated Part L requires replacement windows and doors to achieve a whole-window/door U-value of 1.4 W/m²K or better, or meet equivalent WER/DSER ratings.
• Changes effective 15 June 2022 apply across the board.
• Your installs must use frames and glass that meet that spec -- that's baked into FENSA/CERTASS compliance.

Part K -- glazing safety

• Safety glass in critical locations -- low-level glazing, doors, side panels, and areas where impact is likely.
• Toughened or laminated glass is legally required in these positions.
• Glass suppliers (Pilkington, Saint-Gobain etc.) publish Part K guides on where safety glass must be used.

Fire escape windows

• Building Regs require escape windows in certain locations (bedrooms above ground floor, inner rooms).
• The window must open to a clear opening of at least 450mm high x 450mm wide, with a minimum clear area of 0.33m².
• If you fit a window that doesn't open far enough or has restrictors that prevent escape, that's a Building Regs breach.
• Check every bedroom window you replace - if the existing window was an escape window, the replacement must be too.

BS 8213-4 -- how to install properly

BS 8213-4:2016 is the code of practice for the survey and installation of windows and external doorsets.

It gives detailed guidance on:

• Surveying apertures, checking reveals/DPM and services in the opening.
• Removing old windows carefully, maintaining weathertightness and security.
• Positioning, packing and fixing windows so they're plumb, level and square with correct overlaps to insulation.
• Sealing for weathertightness and drainage, and finishing off properly.

FENSA/CERTASS expect you to work to BS 8213-4, not just "make it look nice".

4. Glass handling safety

Glass is one of the most dangerous materials to handle -- cuts from broken glass are one of the most common injuries in fenestration.

Safe handling

• Always use proper glass suckers/lifters rated for the weight of the sealed unit.
• Carry sealed units on edge, not flat -- they flex and can break.
• Wear cut-resistant gloves when handling glass (even sealed units can have sharp edges).
• Store glass vertically on A-frames or racks, never leaning loose against walls.

When a unit breaks

• Toughened glass shatters into small, relatively safe granules -- messy but unlikely to cause serious cuts.
• Laminated glass cracks but the interlayer holds the pieces together -- usually stays in one piece.
• Annealed (float) glass breaks into large, razor-sharp shards -- this is where serious cuts happen. Handle with extreme care and dispose of safely.

Know which type you're handling before you pick it up.

5. Condensation -- the biggest callback issue

The single biggest customer complaint for window fitters is condensation. Knowing the difference between types saves you a lot of grief:

Between the panes

• This means the sealed unit has failed -- the seal has broken and moisture is getting between the glass layers.
• This is a product/installation issue -- the unit needs replacing.
• If it fails within the warranty period, it's usually covered by the glass supplier's guarantee.

On the inside surface

• This is usually a ventilation issue, not a window fault. New, better-sealed windows reduce draughts, which means moisture from cooking, bathing and drying clothes has nowhere to go.
• This is not your problem to fix (unless you've blocked trickle vents or failed to install them when required).
• Explain to the customer: "Your new windows are working properly -- they're so well sealed that you need to ventilate more than you did with the old draughty ones."

On the outside surface

• This actually means the window is performing well -- the outer pane is cold because the insulation is working, and morning dew condenses on it.
• Some customers panic about this. Reassure them -- it's a sign of a good window, not a bad one.

Having these three explanations ready will handle 90% of condensation callbacks.

6. Insurance

Public liability

• Your PL must cover fenestration installation -- not all standard trade PL policies do. Check the schedule.
• Product liability for units you supply and fit -- if a sealed unit you supplied falls out and injures someone, product liability responds.
• Typical minimum: £2m PL, but many FENSA/CERTASS requirements and commercial clients expect higher.

FENSA/CERTASS insurance requirements

Both schemes have minimum insurance requirements for members. Check their current published requirements before applying.

7. Waste disposal

Old PVC frames and glass need proper disposal:

• Old PVC frames are classed as UPVC waste and should be recycled where possible. Companies like Veka Recycling and Eurocell take old frames for recycling.
• Old glass needs separate disposal -- it can't go in standard glass recycling and usually goes to specialist waste handlers or licensed tips.
• Factor waste disposal into your pricing -- skip hire, recycling charges, and your time to dispose properly. Leaving old frames piled in a customer's garden is not professional.

8. Heritage and conservation area work

Heritage glazing is a specialism that can set you apart early. It commands higher prices, but you need to understand the rules - they're different from standard domestic work.

Conservation officers override Building Control and FENSA

This catches people out. In conservation areas and on listed buildings, the conservation officer's decision on maintaining historical character takes priority over Building Control or FENSA's standard requirements. If the conservation officer says you can't fit a particular frame type because it would alter the character of the building, that's the end of the conversation - regardless of what Part L or FENSA might normally require.

Always check with the local planning authority's conservation team before ordering materials for any conservation area or listed building job.

Heritage glazing manufacturers matter

There are specialist manufacturers producing heritage slimline double-glazed units with slim sightlines that satisfy both thermal performance and conservation requirements. Not all slimline units are equal - using a low-quality manufacturer can mean failed units, poor sightlines, or products that don't pass conservation scrutiny.

Do your research on which suppliers are genuinely trusted in heritage work. The established specialists have a reputation for a reason.

Sealing: breathability is critical on solid-core buildings

This is where a lot of fitters get it wrong on older properties:

• Solid-core buildings (no cavity) have no natural breathability in the wall construction. If you seal timber windows with standard silicone, moisture gets trapped and rots the timber joinery.
• On solid-core buildings: use breathable products like lime mortar or burnt sand mastic on timber frames. These allow water vapour to escape and protect the timber long-term.
• On cavity wall properties: standard sand and cement is acceptable, but burnt sand mastic with oakum is still best practice for a proper, long-lasting seal.

Getting this wrong means you'll be back in two years looking at rotten frames. Getting it right means the work lasts decades.

Sash window repairs: a great entry point

Here's something most new fitters don't realise - repairs and upgrades to existing sash windows often fall outside both conservation approval and FENSA:

• Conservation: as long as you're using a like-for-like product (matching timber, matching profile), sash repairs and upgrades are usually classed as permitted development and don't need prior conservation approval.
• FENSA: because sash upgrades involve the sash components rather than replacing the entire frame, FENSA generally considers this a repair rather than a replacement - so it doesn't need to be notified through the scheme.

This means sash repair and upgrade work is a brilliant entry point for a new fitter. There are untold rotten sash windows across the UK that need attention, and you can build a solid income stream from this work without needing full FENSA registration first. Your biggest priority on this type of work should be offering a strong warranty on the product rather than chasing every formal qualification before you start.

Safety glazing and small panes

One technical point that matters on older properties: any piece of glazing under 300mm cannot be toughened. This creates a problem on period windows with lots of glazing bars and individual small panes, because you can't meet safety glazing regulations with toughened glass in each small pane.

This is where applied glazing bars come in - using one larger pane of glass with applied bars on the surface to replicate the look of individual panes. This approach:

• Improves thermal performance (better U-value from a single sealed unit).
• Solves the safety glazing problem (the single pane can be toughened or laminated to meet regulations).
• Satisfies the visual requirement for multi-pane appearance in heritage properties.

Understanding when and why to recommend applied bars over true divided panes is the kind of knowledge that separates a competent heritage fitter from someone just fitting windows.

See guide 7.17 for more on planning permission requirements.

9. Money: realistic day rates (2026)

Money is comparable to a good chippy, with the same caveat that your rate has to cover van, fuel, waste, quiet weeks, FENSA/CERTASS fees and NVQ/insurance.

10. Domestic vs commercial glazing

Domestic replacement

• PVC, aluminium and some timber windows and doors into houses/flats.
• Lots of small jobs, dealing with homeowners, self-certifying via FENSA/CERTASS, and Part L/K compliance.

Commercial glazing

• Curtain walling, shopfronts, structural glazing, high-rise.
• Usually working for specialist firms, with CSCS-type cards, often IPAF/PASMA etc. required, and more paperwork and lifting/cranage.

First year, you're likely to be on the domestic side with a bit of small commercial shopfront work if your employer does both.

11. 12-month route map

Months 0-3: Get on the tools and learn properly

• Get your CSCS card sorted (see guide S4).
• Start as a mate for a window company -- your job is to carry, protect, and watch how the experienced fitter surveys and installs.
• Focus on:
  • Learning safe glass handling and access, including how to protect customers' homes.
  • Understanding what "good" looks like: plumb/level frames, neat silicone, smooth operation.
  • Safe removal of old frames without damaging reveals or structure.

Months 3-6: Take on parts of the job and start NVQ2

• Ask your employer to support you through GQA Level 2 NVQ in Fenestration Installation (~£800-£1,500).
• Take on more: do your own surveys under supervision, remove and prep openings, position frames and fixings while your fitter partner checks them.
• Start paying attention to Part L U-values and safety glazing rules -- you'll be signing jobs off to these later.

Months 6-12: Become a competent installer and think ahead

• Aim to complete NVQ2 (many providers say 4-8 weeks of assessment once you're experienced enough).
• Be trusted to run straightforward installs (e.g. a couple of windows or a simple back door) with a mate, with your boss checking.
• Start understanding what's involved in FENSA/CERTASS registration:
  • How jobs are notified.
  • What paperwork and photos are needed.
  • How Part L/K compliance is evidenced.

The message: window fitting is a solid trade if you take the standards seriously. If you learn the GQA NVQ units properly, work to BS 8213-4, and treat FENSA/CERTASS as more than just a logo, you can go from "carrying frames" to running your own compliant installation business inside a few years.

Know your worth

The temptation in year one is to say yes to every job that comes your way. Don't. Saying yes to everything means rushing installs, cutting corners on sealing and finishing, and burning out. A busy diary doesn't mean you're earning - five cheap single-window swaps pay less than two proper full-house refits done right. Learn when to say no. Quality window fitting gets callbacks and referrals. Rushing doesn't. Price properly, take the time to seal and finish properly, and the right customers will find you.

What to do next

• Read: Guide S25 -- Choosing a trade and earning potential
• Read: Guide 15.4 -- Your first year self-employed -- what actually happens
• Read: Guide 7.17 -- Do I need planning permission? (for conservation area work)
• Action: Get your CSCS card and find a window installation company that works to FENSA/CERTASS standards and will support your NVQ.

Sources

• Building Regulations 2010, Part L (Conservation of fuel and power) -- legislation.gov.uk/uksi/2010/2214/contents -- U-value requirements for replacement windows and doors.
• Building Regulations 2010, Part K (Protection from falling, collision and impact) -- legislation.gov.uk/uksi/2010/2214/contents -- safety glazing requirements.
• Building Regulations 2010, Part B (Fire safety) -- legislation.gov.uk/uksi/2010/2214/contents -- escape window requirements.
• BS 8213-4:2016 -- Code of practice for survey and installation of windows and external doorsets.
• GQA Level 2 NVQ Diploma in Fenestration Installation -- published qualification specification and unit content.
• FENSA and CERTASS scheme rules -- published requirements for member installers.
• Health and Safety at Work etc. Act 1974 -- legislation.gov.uk/ukpga/1974/37/contents -- general safety duties.

How this site is funded →

Spotted something wrong or out of date? Email us at hello@kilnguides.co.uk.

In crisis? Samaritans 116 123 · Mental health support