Aluminium Valley – 2.4m Length

A leaking valley is one of the most damaging faults a pitched roof can develop. Water pours down both slopes and concentrates in that channel, and if the valley lining is corroded, cracked or poorly lapped, every heavy rainfall sends water straight into the roof structure. Rotten timbers, damp ceilings, ruined plasterwork. It gets expensive very quickly.

Our aluminium valley takes that risk off the table. It channels rainwater cleanly and reliably into the gutter without corroding, cracking or warping over time. Whether you are a roofer stripping a Victorian terrace in Chelmsford, a builder fitting a valley on a new extension in Colchester, or a homeowner sorting out a valley that should have been replaced years ago, this product does the job properly and lasts.

Product Overview

An aluminium valley is a pre-formed metal trough that sits in the internal angle where two pitched roof slopes meet. It collects rainwater running down both slopes and channels it towards the gutter. The valley sits on top of valley boards and beneath the roof tiles or slates, which are cut and dressed to either side of it to create a neat, weathertight finish.

We supply our aluminium valleys in 2.4 metre lengths, which is the standard trade size and covers most domestic valley runs. Each trough is available in three widths: 300mm, 375mm and 450mm, so you can specify the right coverage for the roof pitch and tile type. The valleys can be ordered in mill finish or powder coated to any RAL colour for projects where the valley is visible or where a colour match to the wider roofline is needed. For a fully coordinated finish, pair the valley with our colour coded sealant at the lap joints.

Online Metal Store Ltd manufactures these valleys at our factory in Chelmsford, Essex. We supply roofers, builders and homeowners across the UK with aluminium roofing components that are made locally and designed for British conditions.

Key Benefits

Will not corrode, warp or crack

This is the single biggest advantage over lead. Aluminium does not corrode in acidic rainwater, does not develop fatigue cracks from thermal movement and does not warp under UV exposure. A properly installed aluminium valley will sit in place for 25 years or more without any degradation. In the UK, where roof valleys take a battering from rain, frost and temperature swings, that durability matters.

Lightweight and easy to work with

A 2.4 metre aluminium valley weighs a fraction of the equivalent lead valley. You can carry it up a ladder with one hand, cut it to length with tin snips or a hacksaw, and form overlaps without specialist tools. For roofers working at height all day, that weight difference makes the job noticeably easier and quicker.

A genuine lead alternative

Lead valleys have been the traditional choice for centuries, but the cost of lead has climbed sharply and theft from roofs has become a real problem. Aluminium delivers the same water-channelling performance at a lower price point, with none of the theft risk or brickwork staining that comes with lead. For the vast majority of domestic and commercial roofing projects in the UK, aluminium is now the sensible choice.

Powder coating in any RAL colour

On some roofs, the valley is visible from ground level, particularly on dormer cheeks, front-facing gables or lower roof slopes. A mill finish strip of metal in those situations can look out of place. Powder coating the valley to a matching RAL colour gives you a clean, discreet finish that blends with the surrounding tiles or slates.

Three width options

Not every valley is the same. A steep pitch with plain tiles needs a different trough width to a shallow pitch with large-format slates. Our three sizes, 300mm, 375mm and 450mm, cover the full range of standard valley details you are likely to encounter on UK roofs.

Made in Chelmsford, delivered across the UK

We manufacture these valleys at our facility on Southend Road in Chelmsford, Essex. Orders go out quickly across the country. If you are local to Essex, you are welcome to collect. If you are in Birmingham, Bristol or Aberdeen, we will get them to you.

Technical Specifications

Material: High-grade aluminium

Length: 2.4 metres (2400mm)

Available Widths: 300mm, 375mm, 450mm

Profile: Pre-formed valley trough

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

Suitable For: Plain tiles, interlocking tiles, natural slates, man-made slates, metal roofing panels

Roof Pitch Range: Suitable for standard UK roof pitches (typically 15 to 55 degrees)

Manufactured In: Chelmsford, Essex, United Kingdom

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

Choosing the Right Width

The width of your valley trough depends on the roof pitch and the type of tiles or slates being used. Here is a practical guide:

• 300mm width is suitable for steeper roof pitches (40 degrees and above) with interlocking tiles or smaller format slates. The steeper the pitch, the faster the water runs off, so a narrower trough is adequate.

• 375mm width is the most versatile option and works well across a wide range of standard UK roof pitches (25 to 45 degrees). It provides good coverage for both tiles and standard slates and is the size most roofers reach for on a typical domestic job.

• 450mm width is the right choice for shallower roof pitches (below 30 degrees), larger format slates, or valleys with a high volume of water run-off. It gives you a wider channel and more overlap under the tile or slate course on each side, which provides extra protection on lower-pitched or more exposed roofs.

If you are unsure which width is right for your project, measure the distance between the nearest tile battens on each side of the valley and check the tile manufacturer's recommended minimum valley width. Alternatively, drop us a message with your roof pitch and tile type and we will confirm the right specification.

How to Install an Aluminium Valley

Fitting an aluminium valley is a straightforward process for any competent roofer. Here is how to get it right:

Start by fixing the valley boards between the valley rafters. These should be a minimum of 12mm plywood, cut wide enough to support the full width of the valley trough plus the tile battens on each side. Lay a strip of roofing underlay down the centre of the valley boards before positioning the aluminium trough.

Place the first length of aluminium valley at the bottom, letting it overhang into the gutter. If the valley run is longer than 2.4 metres, overlap the next length by at least 150mm, with the upper piece sitting on top of the lower one so water cannot get behind the joint. Secure the valley with clips or nails at the edges, but avoid fixing through the centre of the trough where water flows. Once the valley is in position, lay the tiles or slates to either side, cutting them neatly along the valley line. For the best appearance, aim for a consistent margin of 100mm to 125mm between the tile edges on each side. At the abutments where the valley meets a wall or chimney, our aluminium roof soakers provide the waterproofing detail at each tile course.

Where Aluminium Valleys Are Used

Domestic re-roofing and valley replacement

This is the most common job we supply valleys for. A homeowner in Brentwood, Basildon or Braintree has an older property with a lead or mortar valley that has started leaking. The roofer strips the tiles back, removes the old valley lining, lays new boards if needed and drops in an aluminium valley. It is a permanent fix that costs a fraction of re-leading. For the roof edge detail on the same job, our aluminium drip trim finishes the perimeter neatly.

New build extensions and dormers

Any time a new pitched roof joins an existing one, you create a valley. Side extensions, rear extensions with catslide roofs, dormer windows. All of them need a valley detail. Aluminium valleys are now the default specification on the vast majority of new domestic builds across the South East and beyond, largely because they perform as well as lead at a lower cost and without the theft risk. On the same project, you may also need aluminium roof flashing where the new roof meets the existing wall.

Commercial and contract roofing

On larger commercial projects, whether that is a school in Southend, a care home in Cambridge or a housing development in Thurrock, specifying powder-coated aluminium valleys in a matching RAL colour gives you a consistent, professional finish. The 2.4 metre length keeps joint numbers to a minimum on long valley runs. Browse our full range of roof accessories to build out the complete roofing specification.

Heritage and conservation projects

While lead is often specified on listed buildings and conservation area projects, there are many heritage-adjacent properties where the planning authority is happy to accept aluminium as a valley material, particularly when it is powder coated to a dark grey or black finish that visually mimics traditional lead. Always check with your local conservation officer, but do not assume lead is the only option.

Coastal and exposed locations

Properties along the Essex coast, the Kent coast, or anywhere exposed to salt-laden air benefit particularly from aluminium valleys. Unlike lead, aluminium does not corrode in saline environments, and unlike GRP alternatives, it will not become brittle over time. Combined with our aluminium half round gutter system, you can specify a complete rainwater management system in aluminium that handles coastal conditions without any issue.

Frequently Asked Questions

What is an aluminium roof valley used for?

An aluminium roof valley is a pre-formed metal trough that sits in the internal angle where two pitched roof slopes meet. It collects rainwater running down both slopes and channels it towards the gutter, preventing water from pooling or leaking into the roof structure. It is a lightweight, corrosion-resistant alternative to traditional lead valleys and is suitable for tiled, slate and metal roof systems.

Is aluminium better than lead for roof valleys?

For the vast majority of roofing projects in the UK, yes. Aluminium valleys are much lighter, fully corrosion-resistant and significantly cheaper than lead. They do not stain surrounding brickwork, they are not a target for metal thieves and they do not develop fatigue cracks from thermal movement. Lead still has its place on listed buildings and conservation area projects where the local authority requires traditional materials, but for standard domestic and commercial roofing, aluminium is the practical, cost-effective choice.

What width aluminium valley do I need?

It depends on the roof pitch and tile or slate type. As a general guide, 300mm suits steeper pitches with interlocking tiles, 375mm covers most standard domestic applications, and 450mm is the right choice for shallower pitches or larger format slates. Always check the tile manufacturer's recommendations for minimum valley width and consult your project specification. If you are not sure, get in touch and we will help you choose.

How do you install an aluminium valley on a tiled roof?

Fix valley boards between the valley rafters, lay a strip of underlay down the centre, then position the aluminium valley trough starting at the bottom and overlapping each length by at least 150mm. Secure the trough at the edges with clips or nails, keeping fixings away from the water channel in the centre. Cut and dress the tiles neatly to either side, maintaining a consistent margin of 100mm to 125mm between tile edges. Seal lap joints with a suitable external sealant.

Can an aluminium valley be powder coated?

Yes. We offer polyester powder coating in any RAL colour. This is especially useful when the valley is visible from ground level, such as on dormer cheeks, front-facing gables or lower roof slopes. A powder coated valley in a colour-matched RAL shade blends with the surrounding tiles or slates and gives the roof a much tidier finished appearance.

How long does an aluminium valley last?

A properly installed aluminium valley will last 25 years or more in normal UK conditions. Aluminium does not corrode, warp or crack, so there is no gradual degradation of the kind you see with lead or GRP over time. It requires no maintenance beyond keeping the valley clear of leaves and debris, which is good practice with any valley material.

Aluminium vs Lead vs GRP: Which Valley Material Should You Use?

Aluminium valleys

Very lightweight, easy to carry up a ladder and straightforward to cut and overlap on site. Excellent corrosion resistance with a lifespan of 25 years or more. Will not warp, crack or discolour. Available in any RAL colour through powder coating. Very low theft risk. No brickwork staining. Fully recyclable. Competitively priced. Compliant with current UK building regulations for domestic and commercial roofing.

Lead valleys

Heavier to handle and more expensive per metre. Good long-term durability in the right conditions, potentially 40 to 60 years, but lead can develop fatigue cracks over time, particularly where thermal cycling is significant. Only available in grey. High theft risk, which is a genuine and growing problem across the UK. Can stain surrounding brickwork and render. Still specified on listed buildings and in conservation areas where the local authority requires traditional materials.

GRP (fibreglass) valleys

Lightweight, pre-formed and relatively cheap upfront. Suitable for many standard domestic applications. However, GRP can become brittle over time, especially under UV exposure, and it is not as easy to overlap or adapt on site as aluminium. Limited colour options. Not always suitable for very low pitches or high water volume situations. Lifespan is typically 20 to 30 years, though this varies with exposure and quality.

For the majority of UK roofing work, aluminium valleys offer the best all-round balance of performance, cost and longevity. They are lighter than lead, more durable than GRP, and adaptable to virtually any roof type. View the full range of trims, flashings and angles from Online Metal Store Ltd for the other components you need to complete the job.

Standards and Compliance

Aluminium roof valleys should be installed in accordance with BS 5534:2014+A2:2018, the British Standard for slating and tiling, which covers valley detail requirements including minimum overlaps, fixing methods and material specifications. The NFRC Technical Bulletin 28 provides additional guidance specifically on valley trough design and installation, and is widely referenced by UK roofing contractors and building inspectors. For new-build projects requiring NHBC warranty sign-off, the valley detail will need to comply with the relevant chapter of the NHBC Standards. Getting the specification and installation right protects the warranty, the building and everyone who lives or works in it.