If you are fitting or replacing a roof window, getting the flashing right matters as much as the glass. Homeowners and installers across the UK ask the same question every week: which VELUX flashing kit do I need for my roof? This guide covers each roof covering, so you order the correct part first time and avoid a leaky loft. We put this together at Skylights Roof Lanterns because we see the same mix-ups come up again and again.
What Is a VELUX Flashing Kit and Why It Matters
A flashing kit is the weatherproof collar that joins your roof window to the roof covering. Without the correct roof window flashing, water can track under the tiles and drip into the room below. This is the real reason so many people search for which VELUX flashing kit do I need before they order a window. Getting this one part wrong can undo an otherwise good installation, so check before you buy.
A kit is not just a strip of lead. It includes an apron, side flashings, and often a drainage gutter, shaped to suit the covering above and below the frame. Roof window flashing must overlap the tiles correctly on every edge, or driving rain will find a way in.
Working Out Which VELUX Flashing Kit Do I Need for Your Roof
The honest answer to which VELUX flashing kit do I need always starts with your roof covering, not the window size. VELUX flashing kit types are grouped by material and profile, and mixing them up is the single most common ordering mistake.
Tile Roofs
Getting your roof window flashing right starts with identifying the covering. Standard interlocking tiles need the EDW or EDJ range, depending on thickness. Plain, flat tiles use the EDP kit instead, since the overlap is shallower.
Slate Roofs
Natural or fibre cement slate uses the EDN flashing kit, shaped for a flatter profile and tighter overlap than tile.
Flat or Low Pitch Roofs
Felt, bitumen, or membrane coverings need a flat roof solution rather than a tiled kit, and the window itself is often a different model built for low pitch use.
Profiled and Interlocking Tiles
Thicker profiled concrete tiles need a taller kit, since the step from batten to tile is deeper than on plain roofs.
If you are still unsure which VELUX window size and matching kit suits your roof, our guide to VELUX window sizes and codes is worth reading before you order.
A Quick Comparison of Common Flashing Kit Types
|
Roof Covering |
Typical Kit Code |
Best Suited To |
|
Interlocking tiles |
EDW / EDJ |
Standard concrete or clay tiles |
|
Plain flat tiles |
EDP |
Thin, flat tile profiles |
|
Natural or fibre cement slate |
EDN |
Slate roofs of most thicknesses |
|
Profiled or thick tiles |
EDL |
Deep profile interlocking tiles |
|
Flat felt or membrane |
Flat roof unit and kit |
Felt, bitumen or single ply roofs |
This table is a starting point, not a final answer. Roof pitch and window model both affect which VELUX flashing kit do I need, so measuring on site still matters.
Common Mistakes People Make When Choosing a Flashing Kit
Buying by window size alone is the most frequent error we see. The frame code tells you glass dimensions, not roof covering, so identical windows on different roofs often need different flashing kit types.
Another slip is assuming flashing kits are interchangeable between brands. Fitting a generic kit to a VELUX frame usually leaves gaps that sealant cannot fix.
People replacing an old window sometimes reuse the existing flashing to save money, but this rarely works, as flashing degrades with age. For more on how roof windows behave over time, our guide to pitched roof window installation covers this in more depth.
New Build Versus Replacement Kits
New build projects usually need a standard flashing kit fitted during first construction, matched to the roof covering. Replacement projects differ, since the existing tiles or slates are already in place.
When replacing an older window, check the VELUX flashing kit sizes against the current opening, not the glass size on the old frame. Roofs settle over the years, so knowing correct flashing kit sizes upfront saves a wasted trip to the merchant.
If you are comparing VELUX against other manufacturers for a new project, our piece on VELUX alternatives available in the UK looks at how flashing compatibility differs between brands.
Building Regulations and Getting It Right First Time
Roof window installation in England falls under building regulations for weatherproofing and, in some cases, permitted development rules. For guidance on what applies to your property, the Planning Portal is a clear government source, and the Health and Safety Executive guidance on roof work is worth reading before anyone works at height.
Getting the answer to which VELUX flashing kit do I need right at the start protects the investment in the window, and a small mistake can lead to a costly repair later.
Final Thoughts
Working out which VELUX flashing kit do I need does not have to be complicated once you know your roof covering and pitch. Measure carefully and check the fit before the tiler leaves site.
If you would rather talk it through, our team can help confirm the right kit for your project, and you can browse our full roof windows collection at the same time. Call us on 0204 538 3079 and we will point you in the right direction.
