Roof window processing kit – everything you need to know

In order to install a roof window, you will need the kit to go with it. Some people call it a processing kit but many call it a flashing kit or a flashing. Flashings are pieces of aluminium that prevent water from entering your property through the small gaps that would be left between your tiles and the roof window. This ensures the window is completely watertight and reduces the changes of mould or damp.

Which flashing kit would suit my roof?

The type of flashing kit is dependent on your roof covering – most people either have interlocking tiles made from concrete or clay, slate in varying thicknesses or plain tiles.

At FAKRO, we design our flashing based on the thickness of the roof covering or tiles. Interlocking tiles can reach up to 120mm so it is important that the flashing is able to accommodate such thicknesses. For that reason, there are 2 different interlocking tile flashing kits – high profiled tile flashing (EHN-A) and profiled tile flashing (EZ_-A). High profiled tile flashing is suitable for tiles up to 120mm and the profiled tile flashing is suitable for up to 45mm tiles ensuring that the window remains waterproof no matter which roof covering you have.

Similarly to tiles, slate roof covering can come in two styles; non-interlocking up to 8mm and interlocking up to 45mm, therefore at FAKRO we have designed flashing kits to suit both. Our EZ_-A flashing can be used for the interlocking slates up to 45mm and for the slates up to 8mm, EL_ flashing is required.

It is important that tiles are properly inspected before a flashing kit is ordered as plain tiles and interlocking tiles look very similar from a distance but upon closer inspection they are much slenderer and have a maximum thickness of 16mm. FAKRO offers a flashing kit specifically for these tiles called EP_ that will help you achieve a snug and secure fit around your new roof window.

Standard vs. Recessed installation

In the case of standard installation, FAKRO roof windows should be fitted on the V level – there are 3 levels on the side of the window; N, V and J. These indicate the level the window should be fitted. V level or standard installation is where the window sits just slightly proud of the roofline – we call this standard as it is the most common.

Let’s see: Standard flashings

Recessed installation is where the window is fitted on the J level and the window therefore sits lower in the roofline. They are most popular, and generally a legal requirement, for conservation areas as the window is less visible and compliments the surrounding historic buildings.

See also: Types of roof windows

Can I combine my roof windows?

We produce specialist combination flashings which allow roof windows to be seamlessly installed side by side or on top of one another. Multiple adjacent windows set out in a bank means that homeowners with limited space can achieve the same exposure to natural light as they would with a lantern.