Installing the Roof Maker Slimline Roof Lantern

Roger and Robin really enjoyed creating our step-by-step guide to installing a Roof Maker Slimline Roof Lantern.

The English language can be confusing especially when you throw in some building terms. We have skylights, roof windows and roof lanterns. A roof lantern is not actually a lantern but a glass structure with pitched sides.

Its purpose is to provide light. They have become very popular because they throw light back into parts of the building that have been made darker by the addition of an extension.

Even with a large patio door across the whole back elevation, it’s surprising how much the daylight falls away as you move back into the original building.

A roof window gives more daylight than a vertical window and a roof lantern being multi-aspect gives more than that. It’s due to the combination of light that comes directly down from the sky and sunlight which comes in at an angle dependent on the time of the year.

The striking thing about Roof Maker roof lanterns is the minimalist design. When you look up you see the sky and not a whole bunch of bulky glazing bars.

This is the thing that delights the customer but what delights the installer/builder/DIYer is just how easy they are to fit. Even if you have never done this kind of job before you will be amazed how easy it is.

Fitting the Window

The first thing you need to know is that all Roof Maker roof lanterns are made to measure but before you construct your opening and build your kerb you need to look at the size chart because there are certain principles of geometry and structural strength that come into play.

The pitch is 46 degrees which happens to be the optimum for self-cleaning glass, this means that the wider you go the higher the lantern. This might not be a consideration but if you are building an extension you might not want the roof lantern obscuring the view out of the bedroom windows, you might also find that the planning consent stipulates a maximum height.

This is often easy enough to overcome if you have two or more lanterns. The chart shows how you need to narrow the width of the window as you increase the length. This is purely so the weight of the glass is supported.

The next consideration is heat loss. Under Building Regulations, you may be restricted on the amount of glazed area you can have. The good news is that the energy efficiency (U value) of the sealed units and structure is so good that you may be able to have a larger size than you would with some other units.

The lower the U value the better. If you can’t quite achieve the figure you need you can choose the option of triple glazed sealed units which dramatically lower the U Value and also cut out noise from aircraft and traffic.

In most cases, the base perimeter frame comes ready assembled. This is only possible because the company uses its own transport. The other benefit of this is that your lovely new lantern does not have to run the gauntlet of couriers who tend to throw things around.

I can’t begin to count the number of jobs I have done that have been delayed by goods damaged in transit.

Somewhat unusually the Roof Maker frame is fitted before the roof membrane or fibreglass. This means that you don’t have to fit in with somebody else’s schedule. Once the frame is screwed to your built up-stand (kerb) the minimalist frame is constructed and held together with machine screws.

It is hard to imagine how anybody could get this part wrong but the bit you could get wrong is putting in the glass. All I can say about fitting glass, in general, is that it is essential to have a plan.

Before you carry the glass onto the roof you need to work out the route, check for hazards, decide on the method, who is doing what and who is in charge. The last thing you want is a variation on the Chuckle Brothers “To me, to you, to me”.

I would also recommend a pair of professional-grade glass lifting suckers for lowering the last panes onto the frame. These can be bought or hired if you are a DIYer just doing a one-off job.

There are a few bits of siliconing to do to complete the job. If you are not experienced with silicone grab a tub of wipes so you can remove any unwanted smears straight away.

The final bit of siliconing around the bottom edge of the frame must be done before the roof covering is applied and when this is done the glass structure is watertight and draught-proofed.


Whether you do the job yourself or use professionals the end result is a window that gives you superb insulation and the most daylight you can possibly achieve. The question I get asked a lot regarding roof windows is “Will it leak?”.

I can put my hand on my heart and answer that, fitted properly, it will never leak and fitting it properly is amazingly straightforward.

The kind of problems people experience with older style PVC roof lanterns which depend on gazing gaskets can’t happen because the glass is on the outside of the structure not in it.

About Dylan Garton

Dylan Garton is a co-founder, video producer and editor for the Skill Builder social media platforms.

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