The Importance Of A Five Degree Pitch
With any roofing structure, one of the main objectives will always be for it to be designed and built to prevent water and dirt from pooling on the glass. This rule applies to any rooflights you may want to install as well.
Selecting the correct angle for your installation will make all the difference in the long run, especially when it comes to extending the working life of the structure.
Let Gravity Work For You
Everything boils down to simple physics, as it is only natural that water and dirt need to be able to easily roll off of the fitting to prevent further damage. In the event that you devote considerable time and resources to installing a skylight, while at the same time forgetting to place it at the correct angle, you could see your investment wasted.

When discussing the benefits of flat rooflight installations, it would be very easy to assume that this would need to be installed with a completely zero degree angle. However, in this instance, ‘flat’ should not be entirely ‘flat,’ as this would lead to excess dirt and water having nowhere to go and run off.
If you picture spilling a glass of water onto a regular table, you will notice that it just stays there until it is mopped up – this is far more complicated to perform on a flat rooflight! Instead, a minimum of a five degree pitch should be used (the maximum being 30o).
Determining the correct pitch is crucial for efficient water runoff in your flat glass rooflight. A five degree pitch, equivalent to a 9mm rise every 100mm or 87mm rise per meter, can achieve the desired 5 degrees. However, it’s essential to consult with your supplier. Factors such as glass thickness and rooflight span must be considered, especially for larger rooflights, which may require an increased pitch, potentially up to 15 degrees. Ensure a precise calculation to optimize the performance of your rooflight installation.

If you’re crafting your flat glass rooflight, ensure you place the pitch at the top, where the upstand meets the rooflight. This positioning is crucial for optimal aesthetics. Some rooflight offer flat upstands, prompting you to add the pitch at the bottom, thereby altering the upstand’s angle. For a seamless and efficient rooflight solution, prioritize proper pitch placement at the top.
Avoiding Excess Build Ups
There are two main reasons for not wanting excess water and dirt to remain on a skylight for any extended period of time.
First of all, water pooling and evaporating on the flat surface will leave watermarks on your glass, not a good look.
More importantly, the dirty and stagnant water could result in the growth of algae and other unwanted substances on the surface of your skylight – at the very least this will be an unsightly and therefore unwelcome addition to your property, severely restricting the light passed through to your interior. With an angle of five degrees, the water and dirt will simply wash away.
Protect Your Home
If you believe that mould and other growths are enough of a problem on the outside, you may also be interested to know that seeping moisture from a damaged roof could end up damaging the internal walls and ceilings below.
Interior mould and moisture is far more than just an aesthetic issue, and it can actually pose a serious health hazard. Over a long time, constantly breathing in these poisonous ingredients has the potential to lead to severe respiratory illnesses, and it is therefore sensible to protect any building with a five degree roof slope.
To achieve the desired angled you may be able to place the upstand directly onto the roof firrings. Firrings give a flat roof its fall, this will translate the roof pitch onto the roof light. Alternatively if your fixing onto level roof joist, firrings will need to be placed under the upstand or the pitch can be built into your upstand if yourself or your builder is building it.
Exceptions When Pitch Isn’t Needed
Not every rooflight requires a pitched angle. For walk-on rooflights, a flat design is acceptable, but regular cleaning is essential to maintain clarity. If your roof already features a 5-15 degree pitch, the upstand is generally flat, allowing the rooflight to seamlessly follow the roofline. At EOS Rooflights, we offer upstands in both flat and pitched designs to suit diverse installation needs.

Avoiding Excess Build Ups
There are two main reasons for not wanting excess water and dirt to remain on a skylight for any extended period of time.
First of all, water pooling and evaporating on the flat surface will leave watermarks on your glass, not a good look.
More importantly, the dirty and stagnant water could result in the growth of algae and other unwanted substances on the surface of your skylight – at the very least this will be an unsightly and therefore unwelcome addition to your property, severely restricting the light passed through to your interior. With an angle of five degrees, the water and dirt will simply wash away.
Protect Your Home
If you believe that mould and other growths are enough of a problem on the outside, you may also be interested to know that seeping moisture from a damaged roof could end up damaging the internal walls and ceilings below.
Interior mould and moisture is far more than just an aesthetic issue, and it can actually pose a serious health hazard. Over a long time, constantly breathing in these poisonous ingredients has the potential to lead to severe respiratory illnesses, and it is therefore sensible to protect any building with a five degree roof slope.
To achieve the desired angled you may be able to place the upstand directly onto the roof firrings. Firrings give a flat roof its fall, this will translate the roof pitch onto the roof light. Alternatively if your fixing onto level roof joist, firrings will need to be placed under the upstand or the pitch can be built into your upstand if yourself or your builder is building it.
If you are in any doubt about the most effect design for a rooflight, albeit flat or otherwise, it is reassuring to know that our team of experts at EOS Rooflights are available to answer any questions that you may have.
Our expertise are built upon our many years of experience in this field, and our team combined have been responsible for countless quality roofing installations. To get in touch by telephone, simply call 0208 462 3557, or we can also be contacted directly via email.
Contact our team
If you have any questions, would like a bespoke price or want to enquire about our installation service. Give us a call or drop an email:
0208 462 3557