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Various Rooflight Sizes and how to Choose Between Them

When deciding to install a rooflight, it is important to consider various rooflight sizes and how they may benefit or be a detriment to your room. Installing a rooflight that is too big can make your room far too bright and may be too heavy for your ceiling, whereas a rooflight that is too small may be essentially pointless. 

In this article, we’ll discuss different rooflight sizes, the benefit of opting for a bespoke rooflight, and the rooflight types you could choose from.

Size Matters


The purpose of a rooflight is to draw more light into your building and create an aesthetically pleasing focal point for your room, no matter how big or small. Rooflight sizes can influence the look and feel of your building and can be an expensive investment, so it’s important to get it right. 

When comparing rooflight sizes, it is important to note that some rooflight types will offer more benefits than others, even if they’re smaller. For example, a Korniche roof lantern is pitched and has panes pointing at different angles, which will provide a larger surface area for light to ingress from. 

So, before we can discuss the rooflight sizes you could choose from, we’ll first cover the various rooflight types and how they perform compared to one another.


Types of Rooflights

Each of the rooflight types offers its own benefits and advantageous properties that will affect natural light transmission. So, before you choose the size of your rooflight, you should consider how these differently shaped rooflights may give you more bang for your buck, depending on what you’re looking for. 


  • Flat Rooflights 


Here at Lonsdale, we offer a range of flat rooflights that are each designed for different purposes. For example, our fixed rooflights are simple non-opening, non-fragile rooflights that are ideal for use in well-ventilated or air-conditioned buildings. 

We also offer continuous flat rooflights, which offer great flexibility when it comes to sizing. Although we make them at a standard size of 2.5M, you can include as many or as few panes as you like in your order. They’re an easy-access rooflight solution that allows superior light transmission and accessibility. 

Additionally, we have walk-on, access, and opening rooflights which each host their own benefits, and offer a similar level of light ingress. 


  • Roof Lanterns


Our range of SpanGard Roof Lanterns has a far larger surface area than any of our flat rooflights. This surface area will allow far more light into your building than any other type of rooflight, regardless of its size. So they’re worth considering in your search! 

Standard Rooflight Sizes


With so much variation in rooflight sizes across the industry, the concept of a ‘Standard’ sized rooflight seems quite redundant. The existence of the bespoke rooflight creates a magnitude of size options to choose from, but there are a few basic sizes you can start from. 

Here at Lonsdale, the smallest standard-sized rooflight we offer is 600 x 600mm, and stretches up to 2000 x 1000mm. But don’t feel as though you have to stick to this! If you’re looking for a bespoke rooflight, we can manufacture any sized rooflight you need. 

We understand that the rooflight that may work for someone else’s building may not work for yours. So don’t feel confined to particular sizes! 


How do you Measure a Rooflight?

The rooflight sizes that will be appropriate for your building will greatly depend on the size of your ceiling, and the size of the external kerb dimensions of the rooflight. 

The width dimension is usually measured by determining the distance between the structural rafters, and the length is the distance between the inside faces of the trimmers. The measurements of flat rooflights often include the external kerb and the opening of your rooflight. 

Once you’ve measured the area you’d like to install your rooflight, you can exclude rooflight sizes that won’t be suitable for your building.



There are a few aspects you should consider when choosing between rooflight sizes, especially when it comes to the structural integrity of your building. 


  • Stability


We manufacture our rooflights from lightweight materials. But the bigger a rooflight gets, the more inherently weighty it will be. You may have the space for a rooflight of a particular size, but you should consider whether your roof will be able to support it. 

It is always worth testing your roof before purchasing your bespoke rooflight, as they’re non-refundable and could cause an accident if installed on an unstable roof. 


  • Privacy


You should consider the privacy of those in your building before installing a large rooflight. Although it may look nice, you may feel spied on depending on the positioning of your rooflight. If your home or building is placed in an area where your building can be peered into from above, you may want to consider installing a smaller rooflight. 


  • Lighting


If you’re hoping to lessen your energy consumption long-term, a bespoke rooflight is a great way to do so. However, you should consider the positioning of your rooflight before you install it so you can achieve maximum efficiency. 

If you’re installing your rooflight in a north-facing room, which is the coldest and darkest room in a building, you will need to install a bigger rooflight to compensate for the inherent disadvantage. 


The Benefits of a Bespoke Rooflight

The overarching benefit of bespoke rooflights over pre-sized rooflights is that you can do anything you’d like with it. Whether you want a specific shape, size, height, or glass type, a bespoke rooflight will adhere to your requirements. 

Here at Lonsdale, we specialise in manufacturing competitively-priced bespoke rooflights of any size for our customers. So if you’re looking for a bespoke rooflight for your home or business, please don’t hesitate to contact us.