Velux Windows: Why They Cost More Than You Expect

“I can buy a Velux window online for £400. Why are you quoting me £1,800 to fit it?”

I get some version of this question at least twice a month. And honestly, I understand the frustration. The price gap between the product and the installed cost seems ridiculous until you understand what’s actually involved.

Let me take you behind the scenes of what a proper Velux installation actually involves - and why those quotes aren’t as inflated as they seem.

What You’re Actually Paying For

When you buy a Velux window, you’re buying the window. That’s it. The installation is a completely separate project, and it’s where the real complexity lives.

Here’s what that installation involves:

1. Opening Up Your Roof

Your roof is designed to be a sealed, weatherproof barrier. We need to deliberately break that barrier, remove sections of:

• Roof tiles or slates
• Sarking felt or membrane
• Roof battens
• Possibly rafters (if the opening doesn’t align with existing rafter spacing)

This isn’t like cutting a hole in drywall. Every piece we remove needs to be carefully set aside for reuse or proper disposal.

2. Structural Modification

Here’s where it gets expensive. A standard Velux window is typically 780mm wide. Standard rafter spacing in British houses is often 400mm or 600mm centres.

That means we almost always need to cut through at least one rafter. Once you cut a rafter, you need to create a “trimming” frame:

• Trimmer rafters on either side (doubled up for strength)
• Header boards above and below
• All connections properly fixed with joist hangers or structural screws
• Sometimes additional noggins for rigidity

This is structural work. It needs to be done correctly, or your roof’s integrity is compromised.

3. Weatherproofing

The Velux window comes with a flashing kit (usually sold separately, £150-250). But fitting this properly is an art.

The flashing needs to integrate with:

• Your existing tiles/slates
• The roofing membrane
• The window frame itself

There are about 12 different flashing pieces that all need to interlock correctly. If any single piece is wrong, water gets in. And you won’t know about it until there’s staining on your ceiling months later.

4. Internal Finishing

From outside, the window sits in the roof. But from inside, it sits in a “tunnel” through the insulation and ceiling.

This tunnel needs:

• Framing to create the opening in the ceiling
• Plasterboarding (usually tapered for better light distribution)
• Plastering or finishing
• Often painting/decorating

Some roofers include this; others don’t. Always check what’s included in your quote.

5. Insulation Continuity

Your attic insulation probably runs across the ceiling joists. The Velux opening creates a gap. This needs to be properly insulated around the frame, or you’ve just created a thermal bridge and potential condensation point.

The insulation collar for a Velux window costs £80-120, plus the labour to fit it correctly.

Real Costs: What You’ll Actually Pay in UK

Let me break down genuine pricing for different scenarios:

Single Velux in Existing Roof

Component	Cost Range
Velux window (M04 size, most popular)	£400-600
Flashing kit	£150-250
Insulation collar	£80-120
Labour (2 people, 1 day)	£600-900
Scaffolding (if needed)	£250-400
Internal finishing (basic)	£200-400
Skip/waste disposal	£100-150
Total	£1,780-2,820

For a standard installation with typical access, expect £1,800-2,200 all-in.

Multiple Windows (Same Project)

The good news: multiple windows are cheaper per unit because the setup costs are shared.

Number	Cost Per Window (Approx)
1 window	£1,800-2,200
2 windows	£1,500-1,800 each
3 windows	£1,300-1,600 each
4+ windows	£1,200-1,500 each

Velux CABRIO Balcony Window

These are the impressive ones that open out to create a small balcony. They’re stunning, but the cost reflects the complexity.

The window unit itself is £2,500-3,500. Installation is more complex because:

• Larger structural opening required
• More complex flashing system
• Often requires planning permission
• Safety rails and building regulation compliance

Total installed cost: £5,000-8,000

Electric/Solar-Powered Velux

Adding electric operation to any window adds £500-800 to the window cost, plus electrical work for hardwired versions.

Solar-powered versions are easier (no electrician needed) but cost more upfront.

Additional cost for electric: £600-1,200 total

Why Some Quotes Are Higher Than Others

If you’re getting quotes that vary by £500 or more for the same window, here’s what might explain it:

Scaffolding Requirements

Some roofs can be safely worked on from a ladder. Others absolutely need scaffolding. If your roof is:

• High (more than 1 storey)
• Steeply pitched (over 35 degrees)
• In a location with poor access

Scaffolding adds £250-500 to the job.

Internal Finishing Scope

A “basic” finish is plasterboard and skim, unpainted. A “complete” finish includes:

• Tapered reveals for better light distribution
• Full plastering
• Painting to match your room

The difference can be £300-500 per window.

Structural Complexity

Some roofs have:

• Older timber that needs reinforcement
• Non-standard rafter spacing
• Existing roof lights being replaced (much easier)
• Trusses instead of traditional rafters (much harder)

Trussed roofs, in particular, can add significant cost. Cutting into trusses often requires an engineer’s sign-off and structural modifications.

Insurance and Guarantees

Roofers with proper insurance and meaningful guarantees charge more than cash-in-hand operators. This isn’t padding - it’s the cost of doing business properly.

Ask every roofer for:

• Public liability certificate
• Employer’s liability certificate
• Their written guarantee terms

The Hidden Factors That Increase Cost

Beyond the obvious, here are things that can push your quote up:

Existing Roof Condition

If we open up your roof and find rotted timber, crumbling battens, or deteriorated felt, we can’t just ignore it. Repair work is additional.

A good roofer will include a “subject to existing condition” clause. This protects both of you.

Access Issues

Can we get scaffolding to the right spot? Can materials be delivered nearby? Is there parking for the van?

Poor access equals more time, which equals higher cost.

Conservation Areas

If you’re in a conservation area, you might need:

• Planning permission for a roof window
• Specific Velux models (conservation style)
• Heritage officer approval

The windows themselves cost more, and there’s additional time for paperwork.

Time of Year

We can’t install Velux windows in the rain (obviously). Booking in winter means a higher risk of delays and possibly a slight premium for the uncertainty.

What the “Cheap” Quotes Miss

I’ve been called out to fix “cheap” Velux installations more times than I can count. Here’s what corners get cut:

Inadequate Structural Support

The rafters get cut, but the trimming isn’t done properly. I’ve seen windows held in by nothing more than the flashing kit - terrifying.

Poor Flashing Installation

The flashing kit comes with detailed instructions. Ignoring them means leaks. Not now, but within 2-3 years when the sealant deteriorates.

No Insulation

The insulation collar gets skipped. For a year or two, you won’t notice. Then you’ll start seeing condensation on the frame, mould around the opening, and wonder why.

Rushed Internal Finish

The plasterboard gets screwed up, given a single coat of jointing compound, and called done. Cracks appear within months.

No Building Regulations Compliance

In UK, new roof windows technically require building regulations compliance for:

• Structural modifications
• Ventilation changes
• Fire safety (in some situations)

Most domestic jobs don’t get formally certified, but a proper installation should at least meet the standards.

Is It Worth Buying the Window Yourself?

You can save money by buying the Velux window yourself and having a roofer install it. But consider:

Potential Problems

• Wrong size ordered (you’re responsible)
• Window damaged in delivery (your problem)
• Missing flashing kit (common mistake)
• Voided warranty if not installed by approved installer

Potential Savings

Typically £100-200 compared to the roofer supplying it.

My Advice

If you know exactly what you need, buying it yourself is fine. But most homeowners don’t know about flashing kits, insulation collars, and the different installation depths for tile vs slate.

Let the roofer supply everything. They’ll order correctly, get trade prices, and take responsibility for the whole system.

The Velux Warranty and Why It Matters

Velux windows come with a 10-year warranty. But there are catches:

What’s Covered

• Manufacturing defects
• Glass seal failure
• Operating mechanism failure

What’s Not Covered

• Installation problems
• Flashing kit issues
• Damage from improper handling
• Condensation (usually considered an installation/ventilation issue)

The Installation Matters

If your Velux leaks and Velux determines it’s an installation problem, their warranty won’t help. This is why using an experienced roofer - ideally a Velux-certified installer - matters.

We can arrange Velux-certified installation that gives you both the product warranty and installation guarantee.

Alternatives to Velux

Velux dominates the market, but they’re not the only option:

Brand	Quality	Price vs Velux
Fakro	Good	10-20% cheaper
Keylite	Good	15-25% cheaper
Roto	Good	Similar
Generic/Budget	Variable	30-50% cheaper

My Experience

I’ve installed all of these. Velux remains my preference for:

• Consistent quality
• Readily available parts
• Flashing systems that actually work
• Long-term reliability

The budget brands can be fine, but the flashing kits are often problematic, and getting replacement parts in 10 years might be difficult.

Questions to Ask Before You Commit

Before accepting any Velux quote, ask:

1. Is the window included, or just installation? (Both should be listed separately)

2. What flashing kit is included? (EDL, EDW, EDS, etc. - depends on your roof type)

3. Is the insulation collar included? (Should be)

4. What internal finishing is included? (Plasterboard? Plastered? Painted?)

5. What structural work is required? (How many rafters cut? What trimming?)

6. Do you need scaffolding? (And is it included?)

7. What guarantee do you provide? (On your workmanship, separate from Velux warranty)

8. Are you a Velux-certified installer? (Not essential, but reassuring)

The Bottom Line

Yes, Velux windows cost more to install than most people expect. But the alternative - a leaking, structurally compromised roof opening - costs far more to fix.

When you’re paying £1,800-2,200 for a properly installed Velux window, you’re paying for:

• Permanent structural modification to your roof
• Weatherproofing that will last decades
• Professional finishing inside and out
• Guarantees that mean something

That’s not expensive. That’s proper building work at fair rates.

Thinking About Velux Windows?

We’ve installed hundreds of Velux windows across UK. We can give you an honest assessment of what’s involved with your specific roof and a fixed-price quote with no surprises.

Call us: +44 89 981 9675

Or request a quote online - we’ll get back to you within 24 hours with clear, itemised pricing.

Natural light transforms attic spaces. Let’s make it happen properly.