Aluminium Roof Flashing – 3000mm Length

Every junction where a roof meets a wall is a potential weak point. If the flashing fails, water gets in. It does not matter how good the tiles are, how well the membrane is laid, or how solid the brickwork is. A dodgy flashing detail will undermine the lot and leave you with damp, staining and, eventually, structural damage.

Our aluminium roof flashing is designed to make sure that junction stays watertight for decades. Supplied in 3-metre lengths and available in five widths, it covers wall abutments, parapet upstands, cladding junctions and flat roof details with a clean, permanent finish. Whether you are a roofer in Chelmsford finishing a re-roof, a builder in Brentwood flashing a kitchen extension, or a cladding contractor in East London wrapping up a commercial job, this product does exactly what it needs to do.

Product Overview

Aluminium roof flashing is a flat, pre-formed metal strip used to weatherproof the junction between a roof surface and a vertical wall. It is the cover layer that sits over soakers, membranes, termination bars or other primary waterproofing components, providing a visible, durable finish that sheds rainwater away from the joint.

We supply this flashing in 3000mm lengths, which is longer than the industry-standard 2.5 metre option and means fewer joints on longer runs. You can choose from five widths: 100mm, 150mm, 200mm, 250mm and 300mm, each available in mill finish or polyester powder coated to any RAL colour. The 3-metre length and range of widths make this flashing suitable for everything from a narrow step flashing cover on a domestic chimney through to a wide parapet wall detail on a commercial building. It pairs naturally with our aluminium roof soakers on pitched roof abutments and our aluminium termination bar on flat roof upstand details.

Online Metal Store Ltd manufactures this flashing at our factory in Chelmsford, Essex, and dispatches across the UK. We produce roofline and weatherproofing components every day, so we understand the details that matter on site.

Key Benefits

3-metre length for fewer joints

Most competitors supply flashing in 2.4 or 2.5 metre lengths. Our 3-metre option covers more wall in a single run, which means fewer overlaps, fewer potential failure points and a tidier finished appearance. On a long abutment or parapet run, that extra half metre per length adds up to a noticeably cleaner result.

Five width options for every detail

Not every flashing detail is the same width. A narrow step flashing cover over soakers on a pitched roof might only need 100mm or 150mm. A wide parapet wall cover that needs to dress over a termination bar and lap onto the roof surface might need 250mm or 300mm. Having five widths in the range means you can specify exactly the right product for the job rather than cutting down an oversized piece or making do with something too narrow.

Powder coating in any RAL colour

On visible details, especially front-facing abutments, dormer cheeks, shopfronts and commercial facades, a mill finish aluminium strip can look out of place. Powder coating the flashing to a matching RAL colour means it blends with the surrounding brickwork, render or cladding and gives the building a much more polished appearance. It also adds an extra layer of surface protection.

Lightweight and corrosion resistant

Aluminium does not rust, does not corrode in acidic rainwater, and does not stain brickwork the way lead can over time. It weighs a fraction of lead flashing, which makes it easier to handle on a ladder and quicker to dress into position. In the UK climate, where rain and damp are constants for most of the year, corrosion resistance is not a nice-to-have. It is the minimum requirement.

A practical lead alternative

Lead flashing has been the traditional choice for centuries, but costs have risen sharply and theft from building sites and occupied properties is a real and growing problem. Aluminium flashing does the same job at a lower price, with no theft risk, no brickwork staining and significantly less weight. For the vast majority of modern roofing work in the UK, aluminium is the smarter choice.

Made in Chelmsford, shipped nationwide

We manufacture this flashing at our facility on Southend Road in Chelmsford, Essex. Orders are dispatched quickly across the country. If you are local to Essex, you are welcome to collect. If you are anywhere else in the UK, we will get the order to you.

Technical Specifications

Material: High-grade aluminium

Length: 3000mm (3 metres)

Available Widths: 100mm, 150mm, 200mm, 250mm, 300mm

Profile: Flat strip (can be bent and dressed on site to suit the detail)

Finish Options: Mill finish as standard, or polyester powder coated (PPC) to any RAL colour

Compatible With: Pitched roof abutments, flat roof upstands, parapet walls, cladding junctions, chimney flashings, dormer details

Works Alongside: Aluminium roof soakers, termination bars, drip trims, copings

Manufactured In: Chelmsford, Essex, United Kingdom

Custom Fabrication: Yes. Powder coated to order. Non-returnable unless faulty.

Choosing the Right Width

Picking the right flashing width depends on the detail you are covering. Here is a practical guide:

• 100mm is a narrow cover strip, well suited to step flashing details over soakers on a pitched roof abutment. It provides just enough cover to dress over the soaker upstand and lap onto the wall face.

• 150mm gives you a bit more cover and is a popular choice for domestic chimney flashings and smaller abutment details where you need a wider lap onto the wall or a deeper dress down over the roof covering.

• 200mm is a versatile mid-range option that works across a broad range of abutment and wall junction details. It is wide enough to provide generous cover on both the wall and roof sides of the joint.

• 250mm suits wider details, including flat roof upstand covers where the flashing needs to dress over a termination bar and lap a good distance onto the roof membrane or covering.

• 300mm is the widest option and is designed for large-scale details such as wide parapet wall covers, deep cladding junctions and commercial facade details where maximum coverage is required.

If you are unsure which width is right, measure the depth of the wall detail and the required lap onto the roof surface, add them together and choose the next size up. A bit of extra width gives you room to dress the flashing neatly without running short.

Where Aluminium Roof Flashing Is Used

Pitched roof wall abutments

This is the classic application. Where a pitched roof meets a side wall on an extension, a party wall between terraced houses, or an adjoining building, aluminium flashing covers the top of the soakers to create the visible weatherproofing line. The flashing is chased or surface-fixed into the brickwork, with the lower edge dressing over the soakers beneath the tile courses. Our aluminium roof soakers sit beneath the tiles and work with this cover flashing to form the complete abutment detail.

Flat roof upstand details

On flat roofs, the flashing dresses over the top of a termination bar and laps down the wall face, covering the membrane termination and providing a clean, weathertight finish. This is a standard detail on domestic extensions, garage roofs and commercial buildings across the UK. Pair it with our aluminium termination bar for the complete upstand specification.

Parapet wall weatherproofing

On buildings with parapet walls, flashing is used at the junction between the inner wall face and the roof membrane. It provides the cover layer above the termination point, directing rainwater back onto the roof surface rather than allowing it to track behind the membrane. On these details, the flashing often works alongside our aluminium flat copings or aluminium sloping copings which cap the top of the parapet wall itself.

Chimney and dormer flashings

Chimneys and dormers create multiple junctions with the main roof surface. The front apron, the side stepped flashings and the rear gutter all need a cover flashing layer. Aluminium flashing in 100mm or 150mm width is ideal for the stepped side details, while the wider options (200mm to 300mm) suit the front apron and back gutter where more coverage is needed.

Cladding and facade junctions

On commercial buildings, flashing is used where cladding panels or curtain walling meet a roof surface or another material. The flashing provides a clean, straight termination line and sheds water away from the junction. On these jobs, powder coating to a matching RAL colour is almost always specified. Browse our full range of trims, flashings and angles for the other components you may need on the same project.

Frequently Asked Questions

What is aluminium roof flashing used for?

Aluminium roof flashing is used to weatherproof the junction where a roof surface meets a vertical wall or other structure. It acts as a cover layer, directing rainwater away from the joint and preventing water from penetrating the building. Common applications include pitched roof wall abutments, flat roof upstand details, parapet wall junctions, chimney flashings, dormer details and cladding junctions. It works alongside soakers, termination bars and other primary waterproofing components to create a complete, lasting seal.

Is aluminium flashing better than lead flashing?

For the vast majority of roofing projects in the UK, yes. Aluminium flashing is much lighter, fully corrosion-resistant and significantly cheaper than lead. It does not stain brickwork, does not attract thieves and does not develop fatigue cracks from thermal cycling. Lead is still specified on listed buildings and conservation area projects where the local authority requires traditional materials, but for standard domestic and commercial work, aluminium flashing is the practical, cost-effective choice that most roofers and builders now prefer.

What width aluminium flashing do I need?

It depends on the detail. For narrow step flashing covers over soakers on a pitched roof, 100mm or 150mm is usually sufficient. For flat roof upstand covers and mid-range abutment details, 200mm is a versatile choice. For wide parapet covers, deep cladding junctions and large-scale commercial details, 250mm or 300mm provides the coverage you need. Measure the depth of the wall detail plus the required lap onto the roof surface and choose the next width up.

Can aluminium roof flashing be powder coated?

Yes. We offer polyester powder coating in any RAL colour. This is especially useful on visible flashing details such as front-facing abutments, dormer cheeks, shopfronts and commercial facades. A colour-matched flashing blends with the surrounding materials and gives the building a much more polished finished appearance. Select your RAL colour when you order.

How do you install aluminium flashing on a wall?

There are two common methods. The traditional approach is to chase a slot into the mortar joint, tuck the top edge of the flashing into the chase and point it over with mortar or sealant. The alternative is to surface-fix the flashing using a termination bar screwed through the top edge, with a bead of sealant along the upper edge. Both methods work well. The chase method gives a flush finish, while the surface-fix method is quicker and less disruptive. The lower edge of the flashing should dress over the soakers, membrane or roof covering with a minimum overlap of 75mm.

Does aluminium flashing work on pitched roofs?

Absolutely. Aluminium flashing is widely used on pitched roofs as a cover flashing over soakers at wall abutments, as chimney apron and stepped side flashings, and as dormer cheek cover strips. It bends and dresses easily on site to follow the roof slope and wall profile. For pitched roof abutment details, it works alongside aluminium roof soakers which sit beneath the tile courses.

Aluminium vs Lead vs Self-Adhesive Flashing: Which Should You Use?

Aluminium flashing

Lightweight, easy to handle and dress into position on site. Fully corrosion-resistant with a lifespan of 25 years or more. Available in any RAL colour through powder coating. Very low theft risk. No brickwork staining. Fully recyclable. Competitively priced and available in a wider range of widths than most lead suppliers stock. The default choice for the vast majority of modern roofing work in the UK.

Lead flashing

Heavier and more malleable, which makes it easier to dress around complex profiles. Good long-term durability in the right conditions, potentially 40 to 60 years. However, lead is increasingly expensive, highly susceptible to theft, and can stain surrounding brickwork and render over time. It also develops fatigue cracks in areas of significant thermal cycling. Still specified on listed buildings and conservation area projects. For heritage work where the planning authority requires traditional materials, lead remains the correct choice.

Self-adhesive flashing tape

The cheapest and quickest option upfront. Useful for temporary repairs or very low-budget projects. However, self-adhesive flashings have a significantly shorter lifespan than metal flashings, typically 5 to 10 years. The adhesive bond degrades under UV exposure and thermal cycling, and the material itself is less durable. Not recommended as a permanent solution on any project where longevity matters. Most building inspectors and warranty providers do not accept self-adhesive flashing as a primary weatherproofing detail on new builds.

For most UK roofing work, aluminium flashing is the right balance of cost, durability and appearance. It lasts, it looks good, and it does not come with the headaches of lead or the compromises of adhesive tape. View our full range of roof accessories from Online Metal Store Ltd for everything else you need on the job.

Standards and Compliance

Aluminium roof flashing should be installed in accordance with the relevant British Standards for the roof type. For pitched roofs, BS 5534:2014+A2:2018 covers flashing details at abutments and other junctions. For flat roofs, BS 6229:2018 sets out best practice for flashing and weatherproofing details at upstands and perimeters. For new-build projects, the relevant NHBC Standards chapter provides additional guidance on acceptable flashing materials and installation methods. Getting the flashing detail right is not just about keeping water out. It protects the warranty, the building and the people who live or work inside it.