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Glass Link Extensions: 10 Ways to Get This Feature Right

glass link extensions connecting timber clad building
(Image credit: Simon Maxwell)

Glass link extensions make stunning additions to all kinds of house styles, from super contemporary properties to period houses, as well as conversions.

A glass link is one of the best ways to approach a number of design dilemmas. Perhaps you're linking a detached garage, an outbuilding or a barn to an existing property or you're building an extension but need to link the old and new due to the position of the new extension.

Designing a link that seamlessly stitches two structures together, is no easy task, however, so what do you need to know to get it right? 

Covering design, structural and practical implications, our guide is here with the top 10 ways to ensure your glass link extension is a sparkling success. 

To get a glazed link extension right you need to consider how it will be installed. The best solutions are those that allow you to conceal the link’s supporting frame so that the glass appears to be the only thing present. 

This is achieved by slotting the glass panes into a steel or aluminium frame, and fixing them in place with structural silicone. Ideally, a really sleek look should be created by concealing a channel within the adjacent structure that hides the frame. You then slide all glass sheets and connections into this channel and structural silicon fixes it in place. 

You can use bolted connections but structural silicone is the typical practice used by specialist glass suppliers. A good structural engineer will know how to do this. 

glass link to brick house

Made from clear laminated glass the panels in this glass link by Ion Glass were individually manufactured to fit precisely within the space. Each wall panel is set into bespoke stainless steel channels at floor level and fixed between stainless steel angles to the walls on either side. Pressed zinc flashings ensure the glass is structurally integral to the building and fully watertight. (Image credit: Ion Glass)

2. Use a Glass Supporting Structure

Steel or aluminium framing is a standard way of supporting the glass, but if your budget allows, you could use glass as a supporting structure instead. This would allow you to deliver a completely seamless, elegant glass box — walls, roof and supporting elements. 

There are many examples of glass being employed structurally as both beams and columns. Whether you can go this route will depend on the structure the glass will be ‘stitching’ to. 

In some instances your structural engineer will be able to design a way to slide the glass into the structure. The key here is making sure that the glass and the structure it’s set into can move independently of one another so that there are no issues with differential movement. In most cases a material such as structural silicon will allow for this to take place.

3. Use Laminated Glass

There is always an interesting debate about which type of glass to use: toughened vs laminated. 

  • Laminated is glass that if damaged will not shatter into a million pieces and immediately fall away — it’s what’s used in car windscreens. 
  • Whereas toughened glass is much stronger and will take more damage before shattering, but when it does get damaged, it will do just that — shatter.

So, laminated is preferred, in such situations. It may not be as strong as toughened glass, but it will stay in place.

If you opt for a seamless glass link extension then there are a few things to keep in mind regarding solar gain. If the space faces due south you’ll need a method of controlling solar gain. This can be done by using some of the structure as shading — structural overhangs, for example. 

There are also specialist solar control glass products which reduce solar heat gain, so you should discuss the options with the specialist glass supplier to see what’s available to you.

Home ventilation is another option…

glass link in barn conversion with flagstone floors

Do consider how you will keep your glass link cool in summer — specialist glass, as well as ventilation will all help. This link has doors in it to outside.  (Image credit: Simon Maxwell)

5. Don't Forget About Ventilation

Although a glass link is essentially just a passage from one building to another, it’s still important to consider how to ventilate it. External doors, windows and rooflights are all good options. This may seem like an obvious design detail, but it’s not one to overlook.

6. Cut Costs By Using Standard Sizes

While striking, a glass link can be an expensive feature to add to your home.

The most affordable glazed links will be those that span the shortest distance between new and old buildings and use standard sizes of extruded steel or aluminium rather than specialist lengths and shapes for roof pitches.

bungalow replacement contemporary design with upper storey glass link

In this self build, designed by Hayward Smart Architects, a glazed link provides a transparent structure between the main house and the garage, with study above.  (Image credit: Fraser Marr)

7. Design Your Glazed Roof With Care

The roof of a glazed link could be solid laminated glass or, alternatively, you could opt for an insulated lantern arrangement, which could be flat or pitched. A fully-glazed roof should never be totally flat. In order to shed water, it needs a slope somewhere between 3º and 5º. 

Designing a solid roof with a central glazed roof lantern will draw light into the centre of the link. The main challenge here will be the thickness. When it comes to roofs, the easy way to get around this is to favour a flat roof with solid laminated glass. The glass specified for such a roof (or wall), is not likely, even if laminated in several sections, to be more than 75mm at the very most.

8. Improve Your Chances of Planning Permission Approval

When it comes to securing planning permission for a glass links, there’s no getting around the need to work within the bounds of what your local planning authority will deem appropriate. Therefore you should have this in mind from the very start of your project. 

If your house is listed, in a conservation area or an area of outstanding natural beauty, you will have to enter into dialogue with the local conservation officer. Conservation officers are there to advise and protect any heritage assets within a defined area. They will judge any proposal on its merits. 

In many cases conservation officers will look favourably on pure, transparent structures like the ones we’re discussing here, as they allow existing structures of historical significance to exist without any visual distraction.

contemporary timber clad extension joined to existing stone house with glass link

This striking self build, designed by Peregrine Mears Architects, is in a conservation area so a sensitive approach was required — the form of the house was based upon a Devon longhouse.  (Image credit: Lawrence Liddy)

Using glass for the entire structure, including beams and columns, will always be the most expensive option. If your structural engineer specifies laminated glass, which has the outer pane heat treated to make it stronger and less prone to damage, the cost would be around £1,500/m2 .

Do think about maintenance when it comes to glass links — and how you might minimise it. All that glazing will need to stay clean if it is to remain a visual asset to your home. 

There are specialist coatings that can be applied to the glass to assist with maintenance and reduce the amount of residue left on the it, including a range of water-repellant applications.

Darren Bray is Technical Director of award winning New Forest practice Pad Studio. He has been a part time studio tutor at Portsmouth School of Architecture since 2007.