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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.

Velux installers offer the Velux Active home kit. This provides an automated system to enhance your indoor living. With its sensor-based ventilation apparatus, the Velux active home kit’s smart sensors repeatedly monitor your home’s temperature, humidity and CO2 levels for its optimum healthy living standards.

Sensor-based ventilation
Velux Active tracks temperature, humidity and CO2-levels, and ventilates to keep your indoor climate nice and healthy.

Automatic heat protection
Velux Active automatically protects your home from excessive heat by closing your Velux Integra blinds, awnings and shutters on hot days.

Set personal preferences
Want to swap your alarm clock for a sunrise or air out while you’re at work? Customise your indoor climate with Velux Active.

Voice-control and smart speaker integration come standard with VELUX ACTIVE with NETATMO, enabling you to draw the shades or open the windows just by asking.

You should inspect your roof at least once a year, to check there are no leaks or infestations. It’s best to do this just after it has rained, so leaks are as obvious as possible. You may find over a period of time there is a build up of moss on the roof, this should be cleaned so rain water has a clear path to the guttering.

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.

Ponding is where you see pools of water appearing on your flat roof. Unless your roof is leaking or showing other signs of damage, you don’t need to replace it. When you do have your flat roof replaced, tell the contractor so they can find out the cause of the ponding.

Most material warranties come from the waterproofing layer manufacturers, and can last between 5 and 20 years. If your roofing contractor is on the manufacturer’s installer list, it might cover their work. It’s important that you always read through all the information given to you about your warranty so you know exactly what is included.

You should inspect your roof twice a year, ideally after rain or snow, to see if it’s draining properly. Also in the Spring to check for damage that may of been caused over the winter months that will need to be put right before the next winter. Have an inspection carried out if you are unsure.

Blisters are most common on membrane roofing systems. Lots of contractors will tell you that if there are no signs of further damage, there might not be any need to repair flat roof blisters. They form when pockets of air or water get trapped between layers of the roof’s membrane or between the membrane and the frame. When the sun is out and it heats the pockets expand and stretch the membrane. If you do want to repair your flat roof blisters, there are a few ways to go about it.

If you have a membrane flat roof, cut away the membrane until you reach a place where the membrane is still stuck tightly to the roof. Reapply as many new membrane layers as you cut away over the blistered area. You might even need to do more. To make sure your patch remains watertight, you’ll need to leave at least 6 inches around the edges of the blister.

If you’ve got a felt roof, you can cut an X shape through the blister. Peel back the triangles that you’ve made and let the timber frame dry for a while (so don’t do this when rain is forecast!). Then, coat the area with lots of bitumen adhesive and leave it to dry until it feels tacky. Then press down the triangles of felt firmly into the adhesive.

After that, you’ll need to add more bitumen adhesive to the cuts you made. If you’ve got any spare roofing felt, cut a square that’s about 100mm bigger than the cuts then lay this over the adhesive. If you’ve not got any felt, it’s cheaper to use a self-adhesive flashing strip. Once you’ve laid the strip or patch over, seal the edges with more bitumen adhesive.