How To Install Skylights

If you are a keen on DIY and have a familiarity with carpentry, you might be thinking about how to install skylights. This can be a good way to keep down costs but you need to be confident in what you’re doing. If in doubt, get a professional to do the work.

How To Install Skylights

Choose where to place the skylight

Deciding which side of the roof to place the glass skylight on is a crucial decision as it will determine how much direct sunlight you are able to capture throughout the day. A south or west facing skylight will receive the greatest amount of sunlight and north or east the least. The former can be hugely beneficial during the colder winter months, but during the summer, you run the risk of the room heating up to an uncomfortable temperature. This can be avoided by adding remote control shades or blinds to your skylight.

Think ahead about how you’re going to install the skylight and try and avoid areas where electrics or plumbing are already present. Choose a point between rafters to avoid making significant structural changes.


Determine the pitch of the roof

Unless you’ve chosen a highly bespoke option, the vast majority of skylights are created for a set roof pitch. You will need to purchase one that matches the pitch of your roof in order to ensure a watertight finish. To make things easier, roof pitch is typically expressed as the number of inches the roof rises vertically for every 12 inches it extends horizontally along the roof’s run. The roof’s run is simply the distance from the edge of the roof to the point directly below the centre of the roof ridge. As an example, if a roof rises 4 inches for every 12 inches of run, it has a 4-in-12 pitch.

By using this ratio, you only need to measure a small section of the roof. If you can get into your attic, we would recommend that you measure the pitch of your roof from the inside. The lack of roof materials on the inside can actually help to give you a more accurate measurement.

First, measure and mark 12 inches on your level. Take the level and rest it directly underneath a roof rafter at the point at which it meets the wall, so that it is pointing into the room. Find the 12 inch mark on the level and then measure vertically up for this point to the roof rafter. This should then give you the number of inches the roof rises for every 12 inches of horizontal run.


Cut a space in the roof for the skylight

To make sure that you cut the hole for the skylight in exactly the right place, we would recommend marking each corner of the rectangle from the inside of the building. This is most easily down by inserting four screws that will then become visible when you remove the external roofing material. You should not just remove the roofing material within the defined area but also anything in the vicinity that could be easily damaged. Connect the marked corners with a chalk line.

When it comes to the actual cutting, we would recommend that you use a circular saw. Have someone else on end hand to catch any falling debris as you make the final cut. This debris might include any installation.


Build the supporting frame

In order to support the skylight in its position, you’re going to need to build a strong supporting frame. Cut sections of wood to fit the length of the rectangle hole, and nail them into place, ensuring that they are level. We would recommend that you insert the nails at angle for the greatest security. This is known as toenailing. Alternatively, you could screw the frame into place with L-frame brackets.


Prevent water leakage and drafts with a membrane

A waterproof membrane will help prevent moisture or wind entering your home or damaging the roof. Prior to fitting the membrane, remove any roofing felt from the area that it needs to cover. Starting from the bottom of the skylight, lay the membrane so that it reaches the very top of the skylight frame as well as extending onto the roof. Membranes are typically self-adhesive so be careful to avoid introducing any crinkles or air pockets as you lay it in place. Ensure that there is a sharp crease at the point where the roof meets the frame.

Around the corners, make sure that the membrane extends beyond the length of the frame. Right at the corner edge of the frame, where you want to try and get the membrane to lie flat around the corner, cut a 45 degree angle. Take the resulting flap and smoothly attach it to the side of the frame around the corner. Simply ensure that the remaining membrane is firmly attached to the roof.

Repeat on each side of the frame until it is entirely covered in membrane.


Add the flashing on top

On top of the membrane along the bottom edge of the frame, lay a strip of roofing material. Fit the flashing over the top, securing it onto the frame with roofing nails. You should be able to buy this to perfectly fit your skylight. This can then be covered with shingles, again attached with nails.

Up the side of the frame, lay single step pieces then a shingle over the top, and then repeat all the way up, keeping to this alternating pattern. The step pieces and shingles should be interwoven.

With the bottom and sides of the frame covered in step pieces and shingles, you just need install the flashing on the top edge (saddle flashing). Make sure that you slide it slightly underneath the roof underlay. You may need to cut a slit in the underlay in order to do this.


Insert the skylight

Slide the skylight on top of the covered wooden frame. We recommend that someone else stands on the inside of the roof to help you position it in place and prevent it from inadvertently falling through. Secure the skylight by inserting screws through the provided metal brackets and into the supporting frame that you’ve already assembled.


If you’re still not sure how to install skylights, at Glass and Stainless we can install your skylight as well as design and produce it. To discuss your specification, get in touch today.