How to Install an Aluminium Roof Lantern on a Flat Roof

Jul 21, 2026 Jamie Robinson

More homeowners across the UK are choosing to install an aluminium roof lantern and take advantage of the benefits they offer:

More natural light
Greater energy efficiency
Better ventilation
Adding a feeling of space to smaller rooms

If you're looking to install an aluminium roof lantern on a flat roof, this guide covers a standard four-pane configuration. Unless you're fitting triple glazing, this applies to sizes up to 3000mm x 1500mm.

Things to Consider Before Installing an Aluminium Roof Lantern

Before deciding on your aluminium roof lantern installation, consider the following:

Do you have the confidence and experience to DIY, or would you benefit from a builder?
The roof structure will usually need structural alterations — cutting joists or rafters and fitting trimmers to carry the weight of the aluminium roof lantern.
Adjacent joists may need strengthening to maintain roof support.
Any aluminium roof lantern must comply with UK building regulations. Installation on an existing roof must be inspected and approved by building control.
Fire performance needs consideration if the aluminium roof lantern is near a boundary.
If roof work could affect bats, a survey may be required.

If you're confident installing an aluminium roof lantern yourself, follow the steps below.

How to Install an Aluminium Roof Lantern on a Flat Roof: Step-by-Step

Step 1: Gather Up Supplies

Check all parts against the inventory before assembling your aluminium roof lantern. The number and type of parts vary by size — all outlined in the inventory list.

Step 2: Measure the Opening

Before buying an aluminium roof lantern, measure the structural opening. The actual size should reflect the aluminium roof lantern you ordered.

For example, a 2,000mm x 1,000mm aluminium roof lantern needs a matching opening. The opening should be 70mm in width to match the built-in upstand. The upstand kerb should have a minimum height of 70mm (increasable if necessary).

Step 3: Prepare the Roof

In most cases, you'll have installed your roof membrane over the ply deck of a flat roof. If so, leave enough extra material around the timber kerb and upstand to weatherproof your aluminium roof lantern when fitted. Fold this material to one side until installation.

We recommend applying the roof membrane after installing the aluminium roof lantern to prevent damage or punctures during fitting.

Step 4: Assemble the Aluminium Roof Lantern Frame

For most aluminium roof lantern sizes, the built-in insulated upstand comes assembled. If your aluminium roof lantern is larger than 3000mm x 1500mm, you may need to assemble the aluminium frame yourself.

Take two corner cleats and slide them into the slots of the aluminium frame. Insert the other end into the matching piece. Ensure nuts and bolts are in pre-drilled holes before sliding the two aluminium frame sections together. Use provided screws to fasten through the top of the upstand. Repeat for all corners, then turn the upstand over and repeat.

Step 5: Connect the Upstand to the Timber Kerb

The upstand is now ready to be fixed to your timber kerb. Apply a thick bead of professional-quality silicone sealant adhesive around the kerb, about 20mm from the inner edge.

Place the assembled upstand onto the kerb, ensuring it sits flush. Insert screws into the groove on the bottom edge of the upstand, 100mm from each corner. Pre-drill holes into the aluminium frame using a standard metal drill bit. Use 12 screws minimum 50mm long — two at each corner, plus one in the middle of each side.

Step 6: Attach the Bars to the Upstand

Attach the four hip bars to the upstand. Place each hip over the upstand and slide the bolt head into the slot. Pull the hip body forward while tightening to keep the internal nut in place. Repeat for each corner.

Ensure the hip body doesn't touch the timber kerb — cut slots in the hip bars if needed.

Now fit the ridge bar. Blocks at either end hold bolts that connect to the hip bars. Slot the grooved end of the hip bars over the screws in the ridge edge block. Position to align with the centre of the ridge bar. Repeat for the other end.

Remove protective film from both sides of the ridge and hip profile. Fit a packer to each corner of the kerb with silicone to prevent sliding.

Step 7: Install the Glass

Insert the glass panels — the heaviest components of your aluminium roof lantern. Peel back a small tab of protective glazing film from the ridge and hip bars.

Lift each glass panel onto the inside groove of the packers, then carefully lower into the aluminium frame, ensuring flush fit. Repeat for all four panels.

Step 8: Install the Carriers and Caps

Once glass is positioned correctly, apply generous silicone sealant into the top and bottom grooves of each hip bar. Run silicone between panels and frames on either side of the hip and ridge bars.

Tap hip carriers and top caps onto the hip bars by hand or with a rubber mallet. Slide hip carriers up so angled cutouts line up, centred to the ridge bar. Arrange so 100mm protrudes at the top — you can't slide hip caps in until the ridge carrier and top cap are fitted.

Run a thick bead of silicone between the glass and ridge bar on both sides. Tap the ridge carrier into place and check it's perfectly centred. Slide the ridge top cap in from one end.

Slide the top caps into place to meet equally at the top centre. Attach the four hip caps to the bottom ends of the hip bars using a screw gun on low gear — don't overtighten. Repeat for all corners.

Install the two ridge end caps. Fill the gap between hip caps and the end of the ridge cover with silicone, then attach.

Step 9: Install the Roof Membrane

Seal the underside of the bottom edge of the glass with silicone. From inside the aluminium roof lantern, gently peel off the remaining glazing film from the hip and ridge bars.

Weatherproof your upstand with your chosen roof membrane. Ensure it's tucked under the drip lip below the glass — this is the final weatherproofing stage to prevent water ingress.

Step 10: Enjoy Your New Aluminium Roof Lantern

Once correctly installed, your aluminium roof lantern will give years of trouble-free pleasure, bringing more light into your home. The room below will enjoy a wealth of natural light, though suitable ventilation is still needed — sometimes through background venting where the product allows.

You'll also benefit from energy efficiency and weatherproofing with low maintenance requirements, thanks to the durable aluminium construction.

Upscale Your Home With Aluminium Windows and Doors

The benefits of natural light have made aluminium roof lanterns, aluminium windows and aluminium doors ever-popular solutions. More homeowners are choosing aluminium bifold doors to take advantage of energy efficiency and ventilation benefits. They also free up space in smaller rooms and create a more aesthetically pleasing home.

With aluminium doors and aluminium windows like ours, you can achieve just that.

Once installed, follow our tips on maintaining your aluminium doors and windows.

FAQs

Do I need planning permission to install an aluminium roof lantern?

Generally, most aluminium roof lantern installations in the UK won't require planning permission, provided:

The aluminium roof lantern sits no more than 150mm from the existing roof plane
It cannot be higher than the highest part of the roof
Side-facing windows may need obscure glazing if overlooking boundaries

Minor repairs affecting less than 25% of the roof area generally don't need building regulations approval, unlike creating a new opening for an aluminium roof lantern.

What should the U-value of an aluminium roof lantern be?

To comply with building regulations, an aluminium roof lantern must achieve a maximum U-value of 2.2 W/m²K. This is set out in Approved Document L-1B. During significant renovations, thermal insulation should be upgraded to reasonable standards to minimise heat loss through the aluminium roof lantern glazing.

How long does it take to install an aluminium roof lantern?

Set aside 3–4 hours to install your aluminium roof lantern, depending on size and whether the opening is already prepared. You'll need a minimum of two people, especially when lifting the glass into the aluminium frame.