Roof Flashing: The Complete UK Guide to Types, Materials and Installation in 2026

Roof flashing is one of those parts of a building that almost nobody thinks about until it fails. And when it does fail, the consequences show up fast: water staining on ceilings, damp patches on interior walls, rot in the timber behind the fascia, and in more serious cases, structural damage to rafter ends and roof decks that costs ten or twenty times what the flashing repair would have cost to get right first time.

The job of roof flashing is straightforward in principle. It creates a watertight seal at every point where two different roof surfaces meet, where the roof meets a wall, and along exposed edges where water would otherwise track behind the covering and into the building structure. Chimneys, valleys, parapet walls, dormer junctions, flat roof edges, the point where a lean-to roof meets a rendered wall: all of these need flashing. Get it right and the roof performs exactly as designed for decades. Get it wrong and the water finds its way in, usually very quietly and very slowly, until the damage is serious.

At Online Metal Store Ltd in Chelmsford, we supply aluminium roof flashing and drip trim products to contractors, developers, architects, and homeowners across the UK. We also supply a full coordinated aluminium roofline system including fascia, soffits, copings, and rainwater goods. This guide covers everything worth knowing about roof flashing before you specify or install: what it is, the different types, the materials in honest comparison, how to install it correctly, and the common mistakes that cause most of the failures we hear about.

This is not a guide written to sell you the most expensive product. It is written to help you understand the subject well enough to make good decisions.

What Is Roof Flashing? Definition, Purpose and How It Works

Roof flashing is thin material, almost always metal or a metal-like composite, that is fitted at joints, junctions, edges, and penetrations across a roof to prevent water from entering the building structure. It works by creating a physical barrier that directs water away from vulnerable gaps and channels it down over the roof covering, into the gutters, and away from the building.

The principle is simple but the execution is what matters. A roof surface, whether it is tiles, slates, flat membrane, or profiled sheeting, handles the broad area of water shedding effectively. But at every point where the continuous roof surface is interrupted, whether by a chimney stack, a dormer window, a wall junction, or the edge of the roof itself, there is a potential route in for water. Flashing closes these gaps.

The reason flashing is so important is that these junctions and edges are where the vast majority of roof leaks actually originate. Tiles and slates do not fail very often. Flat membranes, when correctly installed, are similarly reliable across their main area. The failures concentrate almost entirely at the details: the abutments, the valleys, the edge trims, the pipe collars, the chimney haunches. Get these details right with the correct flashing specification and installation, and the roof will perform reliably for decades. Get them wrong and you are dealing with a leak almost immediately.

Where roof flashing is needed

•      Chimneys: Where the chimney stack passes through the roof slope, flashing is needed on all four sides. The back gutter collects water behind the stack. Step or soaker flashing runs up the sides. An apron flashing covers the front face. Counter flashing is dressed into the mortar joint above and laps over the base flashing to create a two-part weatherproof seal that can accommodate the differential movement between the chimney and the roof.

•      Valleys: Where two roof slopes meet at an internal angle, the valley concentrates all the water running off both slopes. Valley flashing needs to handle a significant water flow and must be correctly shaped to direct water into the gutter rather than allowing it to back up under the tiles or slates on either side.

•      Wall abutments: Where a roof slope meets a vertical wall, either along the slope (side abutment) or at the base (apron or step flashing), is one of the most common points of water ingress on UK buildings. Getting this junction right with the correct overlap, fixing, and sealing detail is critical.

•      Flat roof edges (drip trim): On flat roofs, the edge of the roof membrane needs to be terminated neatly and sealed against wind lift and water entry. Aluminium drip trim provides this function: it holds the membrane edge, throws water clear of the fascia and wall below, and gives the roof edge a clean, finished appearance.

•      Parapet walls: Where a flat roof meets a parapet wall on one or more sides, flashing is needed to seal the membrane upstand against the wall face and to direct water from the parapet down onto the roof surface rather than behind the membrane.

•      Dormers: Dormer windows that project from a pitched roof have multiple flashing requirements: the cheeks of the dormer need step or soaker flashing, the sill needs apron flashing, and the dormer roof itself has its own edge details.

•      Pipe penetrations, vents and skylights: Any penetration through the roof surface needs a collar or flange flashing that seals around the penetration and directs water away from the opening into the roof below

Types of Roof Flashing: A Guide to Every Common Detail

There are a number of distinct flashing types, each designed for a specific application. Understanding what each one does and where it goes is the first step to specifying or installing a correctly weathered roof.

Apron flashing

Apron flashing covers the joint where a roof slope meets a vertical wall at its lower edge. It is a single piece of metal that is dressed flat against the base of the wall above, then folded down and out over the top course of tiles or slates below. The overlap onto the roof covering must be sufficient to prevent wind-driven rain from being forced back under the flashing: typically a minimum of 150mm onto the tiles, and 75mm up the wall.

Apron flashings are one of the most common details on UK buildings, particularly on lean-to extensions, garage roofs, and rear extensions where the new roof slope meets the existing house wall. They are also used at the front face of chimney stacks.

Step flashing and soaker flashing

Step flashing is used at the junction between a pitched roof slope and a vertical wall running along the slope, such as the side of a chimney or the wall of an adjacent property on a semi-detached or terraced house. Individual pieces of step flashing are installed one per tile or slate course, each piece lapping over the tile below and turned up against the wall above. A separate cover or counter flashing is then dressed into the mortar joint above to lap over the exposed top of the step flashing, creating the two-part weatherproof seal.

Soakers are the flat, L-shaped pieces of metal that sit under each individual tile or slate and turn up against the wall. They are hidden under the tiles and form the primary waterproof layer at the junction. The visible step flashing dresses over the soakers and into the wall, providing the second line of defence and the visible finished appearance.

Getting the step flashing and soaker combination right is one of the more involved flashing details. Each soaker must be the correct length for the gauge (exposed width) of the tile or slate, and the step flashing must be correctly dressed into the mortar joint. Poorly executed step flashing is one of the most common causes of persistent roof leaks at wall junctions on UK properties.

Valley flashing

Valley flashing is fitted in the V-shaped channel formed where two roof slopes meet at an internal angle. It handles the concentrated water flow from both slopes and channels it down to the gutter. There are two main approaches: open valleys, where the flashing material is left exposed in the valley, and closed valleys, where the tiles or slates are cut and fitted close to the centre line so the flashing is largely hidden.

Open valleys with a formed metal lining are the most reliable approach for long-term performance. Lead was the traditional material, but aluminium is increasingly used for new installations. The valley lining should be a minimum of 300mm wide, dressed into the roof below the tile underlay, with a correct upstand on each side to prevent water from being blown back under the tiles at the edges.

Counter flashing and cover flashing

Counter flashing is the part of a chimney or wall abutment flashing detail that is fixed into the masonry, usually by cutting a chase (horizontal groove) into a mortar joint and pressing the turned-in edge of the flashing into the chase before sealing with mortar. The counter flashing then laps down over the base or step flashing below, creating a two-part seal that can accommodate differential thermal and structural movement between the masonry and the roof structure without cracking or delaminating.

This two-part detail is fundamental to chimney flashing. A single-piece flashing that is sealed directly to the masonry with mastic or sealant will eventually fail as the masonry moves. The counter-over-base detail is the correct and durable approach.

Drip edge and drip trim flashing

Drip edge is fitted along the eaves (bottom edge) and rakes (sloping sides) of a pitched roof, and along the perimeter edge of flat roofs. Its job is to direct water off the edge of the roof covering and away from the fascia board and soffit below, preventing water from tracking back along the underside of the covering and rotting the timber behind.

On flat roofs, the aluminium drip trim performs an additional function: it terminates and holds the edge of the waterproofing membrane, preventing wind from lifting the membrane edge and providing a clean, weatherproof finish to the roof perimeter. Online Metal Store's 1.5mm aluminium roof edge drip trim in 3m lengths is specifically designed for this application, compatible with single-ply membranes, EPDM, felt, and liquid roofing systems.

Parapet wall flashing

On flat roofs with parapet walls, the waterproofing membrane needs to be turned up the face of the parapet and protected from both the weather and physical damage. Parapet flashing covers this upstand, dresses back over the coping at the top of the parapet, and directs any water collecting on the parapet face back down onto the roof surface rather than behind the membrane.

Coping stones or aluminium copings at the top of a parapet wall serve a complementary function: they protect the top of the parapet from weather and must overhang sufficiently on both sides to throw water clear of the wall face. A well-detailed parapet junction combines the membrane upstand, the parapet flashing, and the coping into a fully weatherproof assembly.

Pipe collar and vent flashing

Wherever a pipe, vent, or service penetrates the roof covering, a collar or flange flashing seals the gap around the penetration. Lead has traditionally been used for these details because of its malleability: lead can be dressed and beaten to take the exact shape of the penetration and the surrounding tiles or membrane. Aluminium collars are available for some pipe sizes, and proprietary rubber or EPDM collars are commonly used for soil vent pipes and gas flues where the penetration is a standard size.

Roof Flashing Materials: An Honest Comparison

The material you choose for roof flashing affects the longevity of the installation, the ease of installation on site, the fire compliance of the finished roof, and the long-term maintenance requirement. Here is an honest assessment of the main options.

Lead flashing

Lead is the traditional UK roofing flashing material and has been used on British roofs for centuries. Its primary advantages are malleability and longevity: lead can be worked and dressed into very complex shapes by hand, and a correctly installed lead flashing typically lasts 60 to 100 years. Lead is specified in codes from Code 3 (thinnest, lightest) to Code 8 (heaviest), with the British Standard BS EN 12588 defining the specifications. Code 4 and Code 5 are the most commonly used for standard residential and commercial flashing applications.

The practical limitations of lead are also worth acknowledging. Lead is heavy, which matters for handling on site, particularly at height. It requires skilled installation: improperly detailed lead flashings can split along stress lines caused by thermal movement if the individual pieces are too long. Current environmental and health regulations in the UK have introduced restrictions on the use of lead in some contexts, particularly in areas where run-off from lead may reach watercourses. And lead has a value as a material, which means lead flashings on accessible roofs are an occasional target for theft.

For further guidance on lead flashing specifications and installation, the Lead Sheet Association publishes comprehensive technical guidance and standard details.

Aluminium flashing

Aluminium is increasingly the material of choice for new-build and replacement roofing flashing in the UK, particularly for flat roof edge trim, drip edge, parapet flashings, and wall abutment applications. The reasons are practical and straightforward:

•      Light weight: Aluminium is approximately one third the density of lead, which makes handling and installation significantly easier on site, especially at height or on complex roofs.

•      No rot or rust: Aluminium forms a natural protective oxide layer that prevents further corrosion. Unlike galvanised steel flashings, a scratch through the surface does not then create a rust risk.

•      Powder-coat colour options: Aluminium flashings can be powder-coated in any RAL or BS colour, which is important for coordinating the flashing with the wider roofline system. Online Metal Store supplies aluminium roof flashing in any RAL colour to match fascia, soffits, copings, and rainwater goods.

•      No theft risk: Aluminium does not carry the same scrap metal value as lead. This is increasingly relevant for commercial and public buildings where lead theft from accessible roofs has been a serious problem.

•      Fire classification: Aluminium achieves A2-s1,d0 under BS EN 13501-1, making it non-combustible and fully compliant for use on all building types including high-rise residential where non-combustible external materials are required under Approved Document B.

•      Recyclable: Aluminium is 100 percent recyclable without loss of quality, which matters for projects with sustainability criteria.

The practical limitation of aluminium compared to lead is that it is less malleable. Dressing aluminium around complex curved shapes and beats is not as straightforward as lead, and for intricate details around irregularly shaped chimneys or heritage masonry, lead remains the appropriate choice. For straight runs, flat roof edges, wall abutments, and parapet details, aluminium is the better practical specification in most cases.

Online Metal Store's aluminium roof flashing range includes 3000mm length flashing strips in 1.5mm gauge, available in any RAL colour, suitable for flat roof edges, parapet abutments, and wall junction details. Our Aluminium Roof Flashing 3000mm and 1.5mm Aluminium Roof Edge Drip Trim 3m are two of our most widely specified products for new-build and refurbishment roofing projects.

Galvanised steel flashing

Galvanised steel flashings are widely used on profiled sheeting roofs for agricultural buildings, industrial units, and large commercial roof structures. They are cost-effective, structurally strong, and well-matched in appearance to galvanised or plastisol-coated sheeting. The limitation is corrosion resistance: if the galvanised zinc coating is damaged, the steel underneath will rust. For long-term installations, particularly in coastal or polluted environments, a plastisol-coated steel or aluminium alternative offers better durability.

Copper flashing

Copper is a premium flashing material most commonly seen on heritage and ecclesiastical buildings, high-end residential developments, and conservation work. Like lead, copper is highly malleable and can be worked into complex shapes. Unlike lead, copper develops a green verdigris patina over time, which some architects specify deliberately as a design element. Copper is expensive, and its price fluctuates with commodity markets. It should not be used in direct contact with aluminium or galvanised materials, as bimetallic corrosion will occur where dissimilar metals are joined in the presence of moisture.

How to Install Roof Flashing: Step-by-Step

This section covers the installation of the most common UK roof flashing details: aluminium drip trim on flat roof edges, apron flashing at a wall abutment, and the general principles that apply to all flashing installation. For complex chimney, valley, and heritage details, the Lead Sheet Association and NFRC guidance should be consulted alongside this overview.

Before starting any roofing work at height, ensure you have appropriate access equipment and that working at height regulations are followed. For most domestic projects, a well-set-up scaffold tower or appropriate ladder with a proper standoff is required. Do not work from a ladder alone on roof surfaces. The HSE working at height guidance provides the full regulatory framework.

Aluminium drip trim: flat roof edge installation

What you will need

•      Aluminium drip trim in the required length and colour (cut to fit, 2mm expansion gap between lengths)

•      Supplied internal joiners for connecting lengths

•      Stainless steel or aluminium screws (not zinc-plated or galvanised, to avoid bimetallic contact with aluminium)

•      EPDM or butyl sealant tape (if additional waterproofing is required behind the trim)

•      Spirit level and chalk line

•      Snips or a fine-tooth metal blade for cutting to length

•      Tape measure and pencil

1.    Mark the chalk line: Snap a chalk line along the timber fascia or roof edge board marking the top fixing line of the drip trim. This ensures the trim runs straight and level along the full length of the roof edge.

2.    Apply sealant if required: On most new flat roof installations, a bead of EPDM or butyl sealant tape is applied to the back face of the drip trim before fixing, to create an additional weatherproof seal between the trim and the timber edge. On a well-detailed roof with a membrane that terminates correctly behind the trim, this may not be required. Check the membrane manufacturer's installation instructions for the specific system being used.

3.    Offer the first length into position: The drip trim should sit with its top face flat on the roof surface (over the membrane edge or the timber board), its vertical face flush to the fascia face, and its profile throwing water clear of the fascia. The trim should extend at least 50mm beyond the membrane edge for the membrane to be dressed under the trim and secure it.

4.    Fix with stainless screws at 400mm to 600mm centres: Fix through the top flange into the timber roof deck using stainless steel screws. Fix at 400mm centres in exposed or high-wind locations; 600mm centres is acceptable for sheltered residential applications. Over-tightening can distort the trim profile: fix snugly but not excessively tight.

5.    Leave a 2mm expansion gap between lengths: Aluminium expands and contracts with temperature. A 2mm gap at every butt joint between lengths accommodates this movement. Over a typical UK temperature range, a 3m aluminium trim length moves approximately 2mm. Use the supplied internal joiners to align the lengths and cover the joint neatly.

6.    Connect lengths with internal joiners: Slide an internal joiner into the profile of one length, then slide the next length onto the joiner. The joiner provides alignment and a clean finish to the joint while allowing the 2mm expansion gap.

7.    Cut and fit the last length: Measure the remaining distance, cut the final length to size with snips or a fine-tooth blade, deburr the cut edge, and fit. Return the cut end into a corner trim or end cap to give a neat finish.

8.    Dress the membrane over the trim: The flat roof membrane should be dressed up behind the drip trim and secured under its top flange. The membrane should not be cut short of the trim or left with an unsealed edge above the trim line, as this creates a point of potential water entry at the junction.

Apron flashing at a wall abutment: installation principles

An apron flashing seals the junction where a roof slope meets a vertical wall at the base of the slope. The principles below apply to both lead and aluminium apron flashings.

9.    Prepare the wall and roof surface: Clear any old mortar, old flashing, or debris from the base of the wall. On new installations, the roof covering (tiles, slates, or membrane) should already be in place up to the base of the wall.

10. Cut the chase if using counter flashing: Cut a horizontal chase into the mortar joint of the wall at the correct height, typically 150mm to 200mm above the roof surface at the abutment. The chase should be approximately 20mm deep and wide enough to accept the turned-in edge of the flashing (typically 25mm).

11. Form or select the correct profile: The flashing should have a top section that turns into the wall chase, a vertical face section, and a bottom section that laps over the top of the tiles, membrane, or roof covering below. The overlap onto the roof covering should be a minimum of 150mm. On aluminium, this profile is typically pressed or pre-formed. On lead, it is dressed to shape on site.

12. Fit the flashing to the wall chase: Insert the turned edge into the prepared chase. Press firmly so it seats flush. Fix with lead clips or aluminium clips at 450mm to 600mm centres to hold the flashing in position before pointing.

13. Point the chase with mortar: Point the chase with a 1:3 cement:sand mortar mix. Ensure the mortar fills the chase fully and covers the turned edge of the flashing. Allow to cure before wetting.

14. Seal the bottom edge if required: On aluminium apron flashings, a small bead of colour-matched silicone sealant along the bottom edge where the flashing meets the tiles provides a secondary seal against wind-driven rain, particularly in exposed locations.

Common Roof Flashing Failures and How to Prevent Them

Most roof flashing failures follow predictable patterns. Understanding them helps both on new installations, where you can avoid them, and on existing roofs, where they help you identify what has gone wrong and what the correct fix actually is.

Insufficient overlap

The single most common cause of flashing failure across all types and materials is insufficient overlap. Apron and step flashings that do not extend far enough onto the roof covering allow wind-driven rain to be forced back under the flashing edge. The minimum overlap onto tiles or slates should be 150mm in normal exposure; in more exposed locations, 200mm or more is appropriate.

On flat roof drip trims, the membrane should be turned well behind the trim and secured. A trim that simply butts against the membrane edge without adequate lap will allow water entry behind the trim within a few seasons.

Excessive flashing length without expansion joints

Lead flashings, in particular, should not be installed in runs longer than around 1500mm without provision for thermal movement. Lead expands and contracts significantly with temperature. A lead apron flashing installed as a single continuous piece over a long run will crack along stress lines at the bends as it goes through repeated thermal cycling. The correct approach is to install individual pieces with a 25mm gap between them, overlapping the lower piece onto the upper by a minimum of 100mm. Aluminium flashings are less prone to cracking but still need the 2mm expansion gap at jointed positions.

Single-part flashing sealed directly to masonry

A common shortcut is to use a single-piece flashing that is sealed directly to the masonry above with sealant or mastic, rather than installing the correct two-part counter-and-base detail. This invariably fails within a few years as the masonry and roof structure move differentially due to thermal expansion, settlement, and seasonal moisture changes. The sealant cracks, opens a gap, and water begins to enter. The correct fix is to install the proper counter flashing detail with a chased fixpoint, not to re-seal a fundamentally incorrectly detailed junction.

Using incompatible materials

Bimetallic corrosion occurs when two dissimilar metals are in contact in the presence of moisture. The less noble metal corrodes at an accelerated rate. Relevant examples in roofing include: copper in contact with aluminium or galvanised steel (copper is far more noble and will accelerate corrosion in both aluminium and zinc); and zinc-plated fixings used to fix aluminium flashings. Always use stainless steel fixings with aluminium flashings, and avoid direct metal-to-metal contact between dissimilar metals at junctions.

Poor mortar pointing on chased details

Counter flashings that are chased into masonry rely on the mortar pointing for their primary fixing. Pointing that is not pressed fully into the chase, that uses a weak mix, or that is allowed to cure too rapidly in hot dry weather will fail within a few years, leaving the flashing loose and the junction open. Use a 1:3 cement:sand mortar mix, work it well into the chase, and protect from rapid drying in hot weather.

Flat roof membrane not turned behind drip trim

On flat roof drip trim installations, the membrane must be turned behind and under the trim, not butted up to it. A membrane edge that terminates at the trim face rather than being secured under it will lift at the edge in wind and allow water entry. The trim and membrane must overlap, with the membrane secured under the trim's top flange, not just alongside it.

Design Uses: How Roof Flashing Works Across Different Building Types

Residential extensions and lean-to roofs

The extension flat roof with a parapet is one of the most common building scenarios in the UK, particularly on terraced and semi-detached Victorian and Edwardian houses where rear single-storey extensions have been added. This construction type concentrates several potential flashing failure points together: the parapet walls need membrane upstand and coping, the roof edge needs drip trim, and the rear wall of the existing house needs an apron flashing where the extension roof meets it.

Getting all three details right together, and ensuring they are compatible with each other, is the challenge. Aluminium drip trim and parapet flashings from Online Metal Store are available in matching RAL colours so the roofline details read as a coordinated system. Our aluminium fascia and soffits and aluminium copings are also available in matching powder-coat colours for a fully consistent specification.

Dormer windows

Dormer windows are complex flashing situations because they involve multiple different junction types in close proximity: step flashing on both cheeks where the dormer sides meet the main roof, an apron at the base of the dormer front wall, a drip or verge detail at the edge of the dormer roof, and a head flashing above the dormer window itself. Getting all of these right together requires careful co-ordination of the detail.

For dormer cheek flashing on a tiled roof, the soaker-and-step detail described earlier in this guide is the correct approach. The lead soakers fit under the tiles; the step flashing is dressed over them into the dormer wall cladding. Aluminium step flashing pieces are suitable where the dormer is clad in aluminium cladding or render that will accept a screwed or pointed fixing.

Commercial flat roofs and new-build developments

On commercial flat roofs, the flashing specification is typically part of the complete single-ply or felt membrane system design. The drip trim, edge trim, upstand trim, and outlet flashings are co-ordinated components within the system, and the membrane manufacturer's installation guide will specify the required flashing details and the acceptable products for use within their warranty conditions.

Online Metal Store supplies aluminium roof flashing and drip trim to commercial contractors and developers across the UK. Our products are compatible with all major single-ply, EPDM, and bituminous flat roof membrane systems. For large commercial projects requiring consistent colour across a significant quantity of flashing components, please discuss batch powder-coating with our team to ensure all units are in the same production run.

Industrial and agricultural buildings

Industrial and agricultural buildings typically use profiled steel or aluminium sheeting for roof and wall cladding. The flashings for this type of construction are matched to the profile and coating of the sheeting: ridge flashings at the apex, verge flashings at the gable ends, eaves flashings at the bottom of the slope, and apron or side abutment flashings where the roof meets masonry walls.

For profiled sheeting roofs, the flashings need to be formed to close the profile gap at the ridge, verge, and eaves. Foam profile closers are used under the flashing to fill the corrugation profile while maintaining the drainage line. The flashing itself must overlap the sheeting by the correct amount for the roof pitch and exposure condition, and must be fixed at the correct centres with the correct washer-head fasteners.

Aluminium Roof Flashing from Online Metal Store Ltd

Online Metal Store Ltd manufactures and supplies aluminium roof flashing, drip trim, and a full coordinated roofline system from our facility in Chelmsford, Essex. All products are made in the UK with fast lead times and UK-wide delivery directly from the factory to site.

Our aluminium roof flashing range

•      Aluminium Roof Flashing 3000mm: 1mm gauge aluminium flashing strip in 3m lengths, available in any RAL colour, suitable for flat roof parapet upstands, wall abutments, and architectural flashing details. Custom widths available on request.

•      1.5mm Aluminium Roof Edge Drip Trim 3m: A purpose-formed 1.5mm aluminium drip trim designed specifically for flat roof edge termination. Compatible with single-ply membranes, EPDM, felt, and liquid roofing systems. Supplied with internal joiners for clean length-to-length connections. Available in any RAL colour.

•      Full aluminium roofline range: Including aluminium fascia (Types 1-4), aluminium soffits, aluminium copings, and aluminium rainwater goods, all available in powder-coated matching RAL colours for a fully coordinated roofline specification.

Batch colour matching for consistent results

One of the most common issues on larger commercial and residential schemes is colour variation between flashing components that were ordered at different times. Powder coat colours can vary slightly between production batches. Online Metal Store batch-matches all roofline components ordered together, ensuring the flashing, fascia, soffit, and coping are all in the same powder-coat colour run and will match visually on the completed building.

For new-build schemes with a specific RAL or BS colour in the architectural specification, please discuss batch requirements with our team at the time of enquiry so we can plan production accordingly.

Custom flashing profiles

Standard flashing strips and drip trims cover the majority of applications, but sometimes a specific profile is needed: a wider apron for an unusually deep roof edge detail, a specific angle for a steeply pitched parapet, or a custom-formed upstand flashing for an unusual architectural detail. Online Metal Store can fabricate bespoke flashing profiles to your dimensions. Please contact us with your sketch or drawing and we will provide a quotation, typically within 24 to 48 hours.

2026 UK Cost Guide for Roof Flashing

The following indicative costs are for planning purposes. Actual costs depend on roof complexity, material choice, access, and local labour rates. Supply costs below are for materials only. Installation costs are in addition.

Frequently Asked Questions About Roof Flashing