Rooflights & Overhead Glazing: Costs, Design Tips & Advice

There’s plenty of options to choose from when it comes to specifying rooflights, roof windows and lanterns. From costs to planning permission, here are the key considerations to bear in mind when choosing rooflights for your self build or renovation project
Rebecca Foster
by Rebecca Foster
23rd January 2024

Rooflights and overhead glazing will make a significant impact on the feel of your home, but the vast array of design solutions to suit self builds, extensions and loft conversions can seem mind-boggling at first.

As an initial step in your journey to buying the best product for your situation, it’s worth getting your head around some of the terminology. According to Building Regulations, a rooflight is, “a glazed unit installed out of plane with the surface of the roof on a kerb or upstand.”

Some manufacturers also refer to this solution as a skylight – but it’s essentially the same thing. On the other hand, a roof window is, “installed in the same orientation as, and in plane with, the surrounding roof.” If you have a bigger budget, you might even be tempted by a roof lantern – an elongated, pyramid-shaped structure that sits on a flat roof.

Each glazing solution provides an effective means of pouring sunshine into your home, as the glass is angled towards the sun, whereas a standard window sits vertically in the wall. Here’s how to approach the buying process and the key factors you’ll need to consider.

Rooflight & Overhead Glazing Designs

If you’re tackling a loft conversion or side return extension with a pitched (sloping) roof, there’s an array of design solutions and opening configurations available. You can choose between centre-pivot and top-opening products, or even balcony-style setups (for attics) that open out to create an area big enough to walk out onto.

“If the space is going to become a bedroom, you’ll want the option to black the room out, so consider whether the product includes a blind or can easily have one fitted,” says Jeremy Dunn, technical director at “If the zone is going to be used as a study or craft space, you’ll require as much natural light as possible, in which case a larger rooflight or roof window might be required.”

Looking for the best glazing product solutions? Browse Build It’s Product Directory of established industry suppliers

Suitable for roof pitches between 35° and 53°, the Velux Roof Balcony opens up extra space to enjoy the sunshine in your attic. The top half of the unit can be used like a conventional rooflight if you don’t want to open the entire setup

Ventilation is another important factor to consider – do you want a fixed overhead window or one that you can open to invite a fresh breeze through? “For openable rooflights, you need to take into account the ceiling height of where the product sits in comparison to the finished floor level,” says Jeremy.

If the unit is within easy reach, then a manually operated solution will typically do the trick. Otherwise, you’ll need to investigate the options for electrically operated products.

If you’re doing a rear extension, incorporating overhead glazing at the back of the addition (where the rear elevation of the house was originally) is a smart way to form a visual break between the old and new parts of the property.

Plus, integrating a roof window here means you can channel light into the zones that sit closer to the centre of the floorplan. Flat roof solutions come in a plethora of configurations, too, whether you want glazing that’s fixed, openable or domed.

Learn More: How to Specify Flat Roof Windows for Your Project

Roof Window Opening Styles

  • Top-hung: Featuring a handle at the bottom of the unit, this solution is hinged at the top so the glass pane opens outwards. As the entirety of the pane opens when the rooflight is open, this configuration tends to offer better views than a centre-pivot design.
  • Centre-pivot: This solution is hinged at the centre, which means that when the rooflight is opened the bottom of the pane tilts outwards and the top tilts into the room. Many products in this category can be rotated through 180°, which makes for easier cleaning than with a top-hung solution.
  • Collapsible balconies: This setup comprises two glazed panels. The top pane sits on the same plane as the roofline when shut and opens in the same way as a conventional top-hung rooflight. The bottom panel opens out to form a vertical balustrade that sits perpendicular to the roof. Velux’s solution, for instance, is attached to a set of rails that slides out of the window to form a dormer-shaped balcony.

Do Rooflights Require Planning Permission?

Most installations are covered by permitted development (PD) rights, providing they do not protrude more than 150mm beyond the plane of the roof slope and do not sit higher than the highest part of the roof.

“If they are on a side elevation, they must be obscure-glazed and either non-opening, or no more than 1.7 metres above floor level,” says Sophie Nguyen, director at Sophie Nguyen Architects. “However, if additional volume is created by the installation, it may be treated as an extension and separate rules apply.”

Roof Lanterns: The Ultimate Buyer's Guide

This orangery project by Welsh Oak Frame features a charming roof lantern with a timber frame inside and powder-coated aluminium exterior. This allows the structure to blend seamlessly with the exposed oak inside the addition while offering a durable, low-maintenance glazing solution

Remember, PD rights don’t apply to listed buildings or those in conservation areas, so if your home falls into either category, you’ll need to apply for consent. “If you live in this type of designated zone, opt for products that use materials and designs that maintain the aesthetic of the building,” says Peter Daniel, innovation director at The Rooflight Company.

“Manufacturers now make high-performing products that look the part, such as our Conservation Rooflight, which takes the look and feel of the original Victorian rooflights and combines it with modern materials.”

Learn More: Conservation Rooflights: Specifying Overhead Glazing For Heritage Homes

conservation rooflights from the rooflight company

The owners of this property, which is located within a conservation area in Henley on Thames, maximised their living space using The Rooflight Company’s conservation rooflights

Which Rooflight Frame Materials Are Best?

Typical options include timber, PVCu, aluminium or steel. Metal solutions have the edge when it comes to creating a sleek aesthetic with minimal framing. “Plus, aluminium can be powder-coated to provide a long-lasting, durable exterior finish,” says Jeremy. It is also lightweight, which makes it easier to install.

“Steel is most often used in conservation areas,” he says. “Timber or plastic are most likely to be used as the internal material, but if the frame is thermally broken, aluminium and steel are commonly used.” Another advantage of a metal frame is that it can be recycled at the end of its useful life.

Timber and PVCu can’t match the innate strength of metal, so tend to result in chunkier frames. On the plus side, wood provides a natural charm that is great on traditional homes. It’s also strong, durable and a natural insulator. Typically, wooden frames require more upkeep than other options as timber can degrade over time if it’s not property sealed or maintained.

PVCu frames are the most affordable option and require no maintenance, aside from periodic cleaning. This material is also corrosion resistant. On the downside, it’s more likely to become brittle in cold weather and typically offers a shorter service life.

More Inspiration: Window Design: Choosing the Right Glazing for Your Project

CASE STUDY Historic home transformed with rooflights

When Caroline and Gustavo Ordonez-Sanz bought this listed property, there was an existing two-storey extension to the rear that had previously destroyed an arched window opening.

Modern SIPs extension

The couple wanted to restore this original feature as it could be used to bring light into the hallway. So, with the help of Paper Igloo Architects, they planned to demolish the existing structure and build a new single-storey extension, combining its historic charm with a new contemporary design.

The single-storey extension has been constructed with structural insulated panels (SIPs) for maximum efficiency and utilises a large rooflight stretching across the ceiling to illuminate the home’s charming stone wall and bring as much light in as possible.

see the home

Are Rooflights Thermally Efficient?

Updated in June 2022, Part L of Building Regs lays out the required standards for rooflight installations. The efficiency of a rooflight or roof window is set out in U-values: a unit of heat loss where lower numbers mean better performance.

The lowest acceptable U-value for a rooflight installation in an existing dwelling is 2.2W/m²K. For a roof window, it’s 1.4W/m²K. In practice, most homeowners will look to beat these figures.

One of the key things to look out for is whether the U-value is for the whole unit or just the centre pane of glass. “The latter can be deceiving as it makes a window appear to be more thermally efficient than it actually is. This is because the measure doesn’t consider the performance of the frame, which is where most heat loss occurs,” says Peter.

U-values for the entire unit may appear less efficient at first glance, but as they include the glass and its surrounds, they actually offer a more accurate measurement of how much heat will be lost.

More Advice: Specifying Energy Efficient Windows: Your Questions Answered

With ultra-slim framing, this roof lantern from Korniche maximises the amount of sunlight that can flood into the room below. There are no visible fixings on show, which makes for a clean, crisp aesthetic

How Much Do Rooflights Cost?

There are plenty of options to suit all budgets. Suitable for roof pitches between 15° and 90°, Velux’s centre-pivot roof window is priced from £305 per unit. For higher-spec solutions, particularly those made bespoke, the cost can easily run into the £1,000s.

Frame material, opening configuration, motorisation and special glass coatings will all affect your overall outlay. “Products on start from £799 if you’re looking at a Glazing Vision Flushglaze fixed rooflight,” says Jeremy. “If you’re looking for a higher spec product that provides you with access to the roof, you can expect to pay as much as £4,599.”

For roof lanterns, you can find good-quality, smaller products starting at around £500. These will suit compact spaces that are after a generous boost of daylight. “Our Slimline roof lantern starts at £473 (+ VAT) for a 400mm x 500mm lantern with toughened, double-glazing and jet-black frame,” says Scott Nicholas, owner of Roof Maker.

According to, homeowners should budget between £800 and £1,100 for professional labour costs. This would cover installation with a flashing kit, collar, insulation and roof alterations. Fitting a roof lantern is likely to cost closer to the £2,500 mark.

“For conservation projects, we particularly recommend choosing a skilled tradesperson who is well-versed in working with heritage properties and period-modelled products,” says Peter. “There are certain nuances that come with installing solutions of this nature, and without the expertise, they can be fitted incorrectly.”

More Inspiration: 31 Amazing Window Design & Feature Glazing Ideas

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