Site prep for a Flat Rooflight
The flat skylight needs to sit on a timber upstand with a five-degree pitch. The upstand needs to be a minimum of 150mm high to satisfy building regulations and a minimum 80mm thick for the rooflight to sit on. Upstands play an important role in ensuring your new skylight sits and fits well. They are the frames that a skylight sits on, creating enough height from the roof surface and enough pitch for the water to run off. Upstands are vital as skylights are not meant to be submerged or have standing water or snow on them. When you place your order with Express Bi-folds Direct we will e-mail the required information to build the correct sized timber upstand for the sized roof that you have ordered.
The rest of the flat roof needs to be covered with a plywood deck, which then needs to be covered with a weatherproof membrane such as GRP or fibreglass.
Before you begin the installation of your new skylight, you will have installed the timber kerb, we also recommend that you apply your roof membrane to your flat roof and upstand to ensure you have a weatherproof flat roof & upstand ready for your skylight to be installed onto.
If you have added your roof membrane on top of your plywood deck already, please ensure that you leave enough excess material around the timber kerb to flash the roof lantern upstand. This can be folded back out of the way until your roof lantern is installed.
You are now ready to begin the installation of your new skylight.
Measuring & creating your timber upstand
The measurements for your flat skylight are the external measurements from the outside edges of your timber upstand. A 1m x 1m skylight needs to sit on an upstand with the same external measurements.
The kerb needs to be a minimum height of 150mm with one edge of the kerb 237mm high to create the five-degree pitch. The pitch is essential to ensure no standing water or snow on the skylight.
The upstand should be perfectly square. We recommend that you check the corners have a 90° angle, by measuring it diagonally from corner to corner. If both dimensions match, then your timber upstand should be square.
Once you have a level and square timber upstand you are ready to start the weather proofing of your roof prior to installing your new skylight.