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Nine things you need to know about glass roofs

If you’re thinking about undertaking a project to let in as much natural light as possible, there are some key points to consider. Today’s glass technology makes for an incredibly strong and durable material – it’s an essential building component – although it does have its limitations. It’s also had some incredible engineering behind it, and, for a price, all sorts of styles and functions are available. Here are nine things to consider before you go ahead.

Courtyard House, East Dulwich

Make sure your walls can support it

This is common sense – the bigger the glazed area, the more glass there is, which can get very heavy indeed. Your structural engineer can help advise you on how much weight your walls can take.

You’ll need steel supports either side and above an opening, such as an external door, or if the roof is particularly heavy. New extensions are constructed with a cavity wall to retain a certain amount of insulation. This is a good thing for your glass roof as the cavity can hide a steel column if you need one.

It’s also a good idea to consider the practicalities of getting the materials on site. For example, check if your large piece of glass can fit through your main entrance door or be carried through to your garden around the side of your house. If not, you’ll need a crane to lift it over your property. Bear in mind potential added expenses like this.

St James
Allow a decent budget

Glass is more expensive than bricks and other building materials. The more you wish your project to ‘disappear’ into the area around it, the more costly the system becomes.

If you would like to keep costs down, choose a glazing system with “off the shelf” sizes and, if suitable, a uPVC or aluminium frame. I only say “if suitable” because when you’re applying for Planning Permission for an extension with a new glazed door or window, you may need to specify the material the frame will be made of, and in conservation areas you may not be allowed to use uPVC or aluminium if this isn’t used anywhere else.

Get 10 great ideas for glass extensions from Houzz

Outdoor Entertaining

Ensure you’ll be able to clean it…

Glass roofs need a minimum slope – the absolute minimum is 1% – so rainwater will help wash away any debris, dust and leaves that settle there. Usually, a slope of 5% or more guarantees a decent enough incline to keep it relatively clean in wet weather or when you wash it.

Make sure you have a good space against which to prop a ladder safely for maintenance, whether you do it yourself or call in a specialist.

Discover more glass roofed spaces by browsing these conservatories

Taybridge Road

…or consider self-cleaning glass

Yes, there is such a thing and it does work! There’s a special, factory-applied coating that makes it harder for dust and leaves to stick to the glass, even on small inclines. It’s similar to the coating your shower screen gets.

This coating can also be retrofitted, but its quality is vastly superior when done in controlled conditions in a factory. It doesn’t mean you should skip cleaning your glazed roof entirely – once every six months is usually recommended – but it may be sufficient to simply hose it down.

Sunshine and elegance in North London suburb
Maximise light with glass beams

In this scheme, the glass roof is supported by glass beams. Adding these will probably be more expensive, but the end effect is stunning – the roof is all glazed!

These beams are toughened and laminated, and your structural engineer will calculate the size and strength they need to be. Each individual piece of glass could end up needing to be as thick as 2cm.

London Town House
Factor in window treatments

Roof windows can help you enjoy the sun all year round. However, sometimes too much sun can make it hard to function – if you want to watch TV without the glare, wish to control the light and create a more romantic atmosphere, or want to keep some of the heat out, for instance. This is when blinds or shutters are very helpful.

It’s important to think about these from the start, so there’s a designated space for them around the windows, especially if they’re custom-sized.

Alternatively, there are specialist glazing systems available that can produce the right finish for your home’s needs – for instance, if you wish to retain as little of the sun’s heat as possible and avoid a ‘greenhouse’ effect. Anti-glare finishes are available in the form of opaque films you can apply to the glass, but be aware they will make the roof light less see-through.

Contemporary Extension Chiswick
Work with a single pane

If you would simply like to have a large piece of glass in the roof in order to brighten a dark room, and you don’t actually need it to open, then you might consider ordering a  bespoke double-glazed unit. Your contractor should be able to get one ordered and fitted for you. You could even have it made to echo your dining table, as shown in this example.

To achieve this look, you’ll need to talk with your builder and structural engineer about the size of roof light you’d like to install so they can judge its location, how they’ll reinforce the structure to accommodate it, and whether they’ll use double joists or small steels around the roof light’s perimeter.

Find 10 ways to incorporate glass into your home

Freezeland Barn
Glaze your whole roof

If you’re creating or refurbishing a loft space, you could use the opportunity to glaze your roof – imagine how much light you could let in! Of course, there are privacy and overlooking issues to be considered as part of the Planning Permission, but any problems can often be solved with opaque glazing or a good-quality adhesive film.

A good guide on whether you’ll be able to get the permission is to check adjacent properties. If in doubt, call the local duty planning officer for advice.

Glass Floor Walk-on Glazing

Make sure you can walk on ground-level windows

Walk-on glass is toughened and laminated. The whole glass unit is usually fitted flush, as shown, with a gap around it, which allows water to run down onto the waterproofing layer of the roof. In this case, the timber decking sits on top of that. This is a great option if you want to usher more light into a basement space, or into a room you’ve built under a large upstairs terrace.

If a special non-slip coating is applied, sometimes in the form of sand-blasted round ‘spots’, it’s safe to walk on the glass with a reduced risk of slipping, too. It should be noted that it does require a specific process to make sure a glazed roof can be walked on safely – and it’s very important to order it as such.

Michael Schienke, Houzz Contributor

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