How to fit a skylight in a pitched roof

St Ives Scaffolding - How to fit a skylight in a pitched roof

A loft space can be one of the most relaxed and inviting rooms in your home if it's given the right treatment. A well-furnished loft will offer an area of quiet solitude and add value to your home. However, lighting is often an issue in modern loft spaces, particularly in homes with pitched roofs. That's why skylights are so popular. A skylight fills the space with natural light, potentially bringing an otherwise rather dour room to life.

Installing a Skylight

Installing a skylight in a pitched roof is not necessarily a job which will require calling in 'the professionals'. It’s always an option, with hundreds of reputable companies able to do a great job, but labour doesn’t come free. In fact, your best option might be to try doing it yourself.


There are two approaches to installing a skylight; external and internal. Depending on whether your roof is slated or tiled, it may be impossible to do the work internally. Removing slate is easier from the outside, while removing tile is easier from inside. In either case, working externally is a much quicker job. Note that you will need specialist equipment like domestic scaffolding and safety harnesses.


Working from the inside, all you'll need is a step ladder and the right tools. It will, however, be a much longer and more involved job. You should be able to fit your window between the rafters, but if there isn't space and you want to cut the rafters to make room, you'll need to consult a structural engineer.


To install a skylight you'll require a variety of tools, most of which you'll probably find knocking about in your garage:

  • Gloves
  • Screwdriver
  • Handsaw
  • Craft knife
  • Spirit level
  • Set square
  • Silicone gun
  • Adjustable spanner
  • Angle grinder (or tile cutter)
  • Lead dresser
  • Stepladder
  • Goggles


Besides the skylights themselves, you'll also need a range of materials to make sure your roof isn't damaged in the process:

  • Lead sheeting kit
  • Two rolls of lead (Code 4)
  • Roof sealant
  • Timer trimmers
  • Wooden battens
  • Wooden fillets
  • Pre-sized slates or tiles


  1. If you're working externally, make sure you've secured the scaffolding (single, bricklayers scaffolding should do the trick) and are strapped in with your safety harness.
  2. Remove the tiles from the part of the roof where you're intending to fit the window.
  3. If working internally, you'll first need to cut away the under-felt, then lift and slide the tiles to remove them.
  4. Cut into your battens to make a space large enough to accommodate the unit.
  5. Screw your timber trimmers into the rafters. They should be around 100mm by 50mm.
  6. Cut out a section of your lead sheet that extends about 150mm past every side of the base and is around 300mm wide. Next, place a wooden fillet along the tiles at the bottom of the opening, then apply roof sealant to the sheet. Then dress the lead.
  7. Pass your up-stand through the window and into the opening, making sure to use a shim if the unit isn't completely level (use your spirit level for this). Then bolt the base plate into the rafters, placing timber packing between the mounting brackets and the rafters if there is any space.
  8. Cut more strips out of your lead sheet and tuck them behind the tiles that you'll be fitting alongside the window. Each strip will be folded around a tile and the next tile will be nailed on top of it. You should now be ready to replace the tiles.

Of course to a layman, this all sounds very confusing indeed. Yet, once you've purchased your skylight (which should come with its own set of instructions) and have your materials laid out in front of you, you'll be surprised just how simple it is.

If this all seems a little daunting and the idea of erecting scaffolding and cutting a hole in your roof completely unsupervised fills you with dread, we certainly wouldn't blame you if you decided to make a quick call to your local carpenter.