Velux Windows in Thames Ditton

Velux windows are a great way to add lots of light to your loft space. Velux is actually the name of a brand of roof window – not to be confused with roof lights, which are usually installed on flat roofs, or skylights, which are normally used to add natural light into a room without being able to open it. Roof windows open like regular windows and are fitted within your roof. But how much are Velux windows? Whether you choose a Velux window or another brand of roof window, they’re not cheap. Since they require special installation, including cutting roof timbers and replacing them to keep the structure strong enough, they take longer to install than a normal double glazed window. It can take up to a day to install a large Velux window, and it could set you back anywhere between £1,600 and £2,000. If you only need a small roof window in an area like a bathroom, you can expect to pay up to £1,300 for it to be fitted. Usually, there won’t be any need for scaffolding or towers because Velux windows are designed to be installed from the inside of your home. However, it’s worth setting aside an additional £500 in your budget in case unexpected problems occur and an installer needs to get on your roof to finish fitting the window. All of these prices are based on a standard roof window without any additional features. If you want to be able to control your windows with an electric switch or remote, this could set you back as much as an additional £400. For extra-low energy glass, you can expect to pay up to £200 more.

Velux windows actually refer to one brand of roof window, which are windows that sit in your roof space and allow light and ventilation into your loft. But how do you install a Velux window? If you’re a competent DIYer, it’s not as difficult as you might think.

You can normally install roof windows entirely from the inside, so you don’t need to get up on your roof or hire costly scaffolding. They come with detailed installation instructions, so as long as you follow them you shouldn’t have much trouble.

Before you start, you’ll need to read up on the Building Regulations and Planning Permission laws. Speak to your local Building Control department if you have any questions.

Firstly, prepare the opening by removing enough tiles or slates from the roof. There’s no need to go out on the roof – access them by cutting away the felt underneath which will give you access to the tiles and battens. Cut away one of the battens from under a tile, then you can slide all the tiles into the roof space. You’ll need to cut away the roof timbers to make the right size opening, then add more timbers to strengthen the ones that are left.

Next, remove the opening sash from the new roof window then fit the frame into the new opening using the brackets provided with the window. Then fit roof flashing between the new window and the roof so you don’t get any leaks. Then lay your tiles back in position around the new Velux window; you’ll probably have to cut some to shape which you can do with an angle grinder. Always cut them on the ground, not in position on the roof.

Lastly, fit the sash back onto the window and you’re done!

If this sounds like too much hard work, plenty of window installers will be able to help you fit a Velux window and will probably be able to provide a much cleaner finish.

In general, no – you don’t need planning permission for a Velux window. The Planning Portal says that you don’t need to apply for planning permission to install a roof window if the following conditions are met:

• A roof window must not protrude more than 150 millimetres above the existing roof plane
No roof window or any other alteration can be higher than the highest part of the roof or stand out above the roof ridge
• Side-facing windows must have obscure glazing to protect privacy of neighbours and, if they open, they must be 1.7 metres above the floor of the room in which they are installed

You don’t need to apply for planning permission for a roof window because they are covered under permitted development rights. However, if you’re a leaseholder or you live in a building where your local authority has made an Article 4 Direction, you will have to apply. Usually, an Article 4 Direction is made when you live in a conservation area where any external home improvements could affect the character and look of the area. Luckily, there are special Velux windows that are designed to be more likely to be accepted by your local planning authority. They’re called conservation windows and, although there’s still no guarantee that they will be accepted, they are designed to look more traditional. Even if you don’t need planning permission for your roof window, you still need to follow any relevant building regulations for your local authority. The most important parts for Velux windows are section J and section L of building regulations, which refer to energy efficiency, thermal insulation and fire protection.

Fitting a Velux window into a slate roof is very similar to the way you’d install it in other roof types. All roof windows, whether a Velux-branded one or not, will come with detailed instructions for you to follow if you want to have a go at fitting it yourself. But here are some brief instructions to give you an idea of what’s involved in installing a Velux window into a slate roof:

1. After you’ve removed the Velux window from its packaging, remove the sash (the part that opens) from the frame, according to the manufacturer’s instructions.
2. Next, you need to prepare the opening for the window. You can often cut through the felt, remove one of the battens from under a slate, then slide all the slate tiles into the roof space. You should then make the cut 40-60mm wider than the window, cutting away roof timbers then replacing them with more around the opening to strengthen it.
3. The roof window’s bottom brackets need to be installed on one of the existing battens for the slate roof. One of the slate courses should line up 105mm below the top edge of the batten you use.
4. Then, measure from the top edge of the batten upwards to the height of the window plus 45mm. This is where the top installation batten should be installed, with an overhang of 100mm on each side.
5. Remove the course of slates below the window, trim any excess felt and fold it over the surrounding timber. This helps with waterproofing.
6. Add the insulation collar according to the Velux window manufacturer’s instructions.
7. Place the frame in the opening, adding the brackets according to the instructions. You’ll find that lots of roof windows have pre-drilled holes to make it easy for you.
8. Replace the sash and line up the hinges. Take a look at the opening at the bottom between the sash and the frame – it should be even along the entire width. Remove the sash again to fix the upper brackets according to instructions.
9. Add the underfelt collar for your roof window as instructed by the manufacturer, then replace any slates at the bottom. You might need to cut them to size.
10. Next, add the flashing according to the instructions, along with any parts that are not yet attached, including the hood section and top flashing piece.
11. Replace all the slates around the window, allowing 60-100mm of space between the course of slates above the window and the top of the window to allow for rainwater drainage. Then replace the sash into the frame again.
12. Add the vapour barrier on the inside of the window using the screws provided, then tape it to the existing vapour barrier to prevent moisture from reaching your roof structure.

And that’s it! If you think that sounds a bit complicated, ask a roofer or window installer to fit your roof window into a slate roof for you. You’ll get a better finish and you can be sure that you won’t get any leaks from a botched installation.