3mm Aluminium Flat Coping – 2m Length | 75mm External Leg

The 3mm flat coping system is the heavier commercial specification. The size range, 510mm to 1060mm, confirms what this product is designed for: cavity wall commercial construction, wider building envelopes, NHBC-registered new-build housing with insulated parapets, and any commercial project where the structural or architectural specification calls for 3mm gauge rather than the lighter domestic 2mm. The 2m section within that system is the right choice for medium commercial parapet faces, for infill positions in longer runs where the remaining face length falls between 1m and 3m, and for any face where a 3m section would waste more than 1m of made-to-order material.

This is the 3mm aluminium flat coping in a 2m length with a 75mm external leg. It is part of the commercial flat coping system from Online Metal Store Ltd, distinct from the 2mm flat coping system in gauge, size range and bracket specification. Manufactured at the Chelmsford facility, powder coated in any RAL colour, made to order and non-returnable unless faulty.

Flat Coping or Sloping Coping: Which Profile?

Both aluminium flat coping and aluminium sloping coping cap a parapet wall and protect it from water ingress. The profile choice depends on the building type, the architectural specification, and the design preference.

Aluminium Flat Coping (This Product)

The flat top surface gives a clean, horizontal profile at parapet level. This is the standard specification for commercial buildings, office developments, retail units and contemporary residential projects where a minimalist parapet line is part of the design. Flat coping relies on the external leg drip detail and correctly sealed joints for weathertightness rather than a built-in surface slope. The 3mm flat coping system is available in 1m, 2m (this product) and 3m lengths in the 75mm external leg range.

Aluminium Sloping Coping

The sloped top surface actively drains rainwater toward the external face. Sloping coping is common on residential flat roof extensions and new-build housing where positive surface drainage is preferred. The 3mm sloping coping equivalent to this product is the 3mm sloping coping 2m length. If the project specification calls for sloping coping rather than flat, use the sloping system throughout: the profiles, corners and stopends are not interchangeable between the flat and sloping systems.

2mm or 3mm Flat Coping: Choosing the Right Gauge

Both gauges are available in the 75mm external leg flat coping range. The profile is the same; the gauge choice is determined by the project type and specification.

Use 2mm Flat Coping When

The project is a domestic flat roof extension, garage, boundary wall or outbuilding in a sheltered setting. The parapet wall produces a coping girth below 510mm. Budget is a consideration and 2mm meets the specification. The 2mm flat coping 3m length and the 2mm flat coping 2m length in the 75mm system cover the domestic and lighter-commercial market.

Use 3mm Flat Coping When

The project is commercial. The parapet wall width produces a coping girth of 510mm or above. The NHBC or structural specification requires 3mm. The site is exposed or the building is two or more storeys. All components on a 3mm installation must be 3mm gauge: lengths, corners, stopends and the 5mm coping bracket. Do not mix 2mm accessories with 3mm lengths.

Product Overview

This 2m section is part of the 3mm aluminium flat coping system with a 75mm external leg, manufactured at the Online Metal Store Ltd facility in Chelmsford. At 3mm, the profile is stiffer than the 2mm equivalent and resists wind uplift forces more effectively over the service life of a commercial parapet. The flat top surface sits level on the parapet, carrying the drip detail over the 75mm external leg. The internal leg is also 75mm, giving a balanced profile on both faces of the wall. The 23 available width sizes, from 510mm to 1060mm in 25mm increments, cover commercial parapet wall widths from approximately 340mm up to 890mm. The 5mm aluminium coping bracket is the correct concealed fixing bracket for this 3mm system.

The 2m section sits alongside the 3m length and the 1m length in the same system. Use 3m sections as the primary lengths for long commercial parapet runs, 2m sections for medium faces and infill, and 1m sections for short faces, final infill pieces and tight-access positions. Every component in the system, including corners, stopends and the bracket, must be 3mm gauge to match.

Key Benefits

3mm Gauge for Commercial Specification

At 3mm, this flat coping section has greater cross-sectional rigidity than the 2mm equivalent. On a commercial building at any meaningful height above ground level, the peel forces generated by wind acting on the coping overhang are higher than at domestic eaves level. The 3mm gauge handles those forces more effectively over the lifespan of the installation. On a commercial project where the coping is expected to perform for 25 years without intervention, specifying 3mm at the outset is the correct long-term decision.

2m Sections for Fewer Joints on Medium Commercial Faces

On a commercial parapet face between 2m and 5m, the 2m section gives fewer joints than 1m sections and less waste than a 3m section where the face does not divide neatly. A 4m face takes two 2m sections with one joint and no waste. Four 1m sections on the same face give three joints. Joint count on a commercial parapet is not just an aesthetic consideration: every joint is a sealant line, and fewer joints means a simpler maintenance position for the building lifetime.

Flat Profile for Clean Commercial Architectural Lines

The flat top surface gives a precise horizontal profile at parapet level. This is the correct choice for commercial buildings, contemporary office and retail architecture, and modern residential projects where a clean, uninterrupted parapet line is part of the specification. Unlike sloping coping, there is no visible tilt or angle on the finished profile: the coping sits level and gives a sharp, consistent shadow line along the parapet at any height.

75mm External Leg, Balanced on Both Faces

The flat coping system with a 75mm external leg has matching 75mm legs on both sides of the wall. This gives a symmetrical profile with equal overhang on the external and internal faces, which is the standard specification for flat coping on straightforward commercial parapets. The sizing formula for this system is simpler than for sloping coping: wall width + 75mm + 75mm + 10mm + 10mm = wall width + 170mm. For the full range of 3mm flat coping accessories, including corners, stopends and upstand stopends, see the 3mm aluminium flat coping section.

Powder Coated in Any RAL Colour

The finish is an external grade polyester powder coat available in any RAL colour. On a commercial project where the coping colour is part of the contract specification, ordering the 2m sections alongside the 1m infill sections, 3m primary sections, corners, stopends and brackets in the same RAL ensures all components are coated in the same Chelmsford batch and arrive colour-matched. Anthracite grey (RAL 7016) and white (RAL 9016) are among the most commonly specified colours for commercial flat coping, but any RAL is available to order.

Technical Specifications

Material: 3mm grade aluminium

Profile: Flat coping length

Length: 2m (2000mm)

External Leg: 75mm

Internal Leg: 75mm (equal both sides)

Width Sizes Available: 510mm, 535mm, 560mm, 585mm, 610mm, 635mm, 660mm, 685mm, 710mm, 735mm, 760mm, 785mm, 810mm, 835mm, 860mm, 885mm, 910mm, 935mm, 960mm, 985mm, 1010mm, 1035mm, 1060mm (23 sizes in 25mm increments)

Wall Width Range Served: Approximately 340mm to 890mm (wall width + 170mm = coping size)

Size Note: The "size" refers to the overall WIDTH of the coping profile, not the run length. All sections on this page are 2m long.

Sizing Formula: Wall width + 170mm = size to order (75mm external leg + 75mm internal leg + 10mm + 10mm returns = 170mm)

Finish: Polyester powder coating, external grade

Colour: Any RAL colour to order

Compatible Bracket: 5mm Aluminium Coping Bracket -- NOT the 4mm bracket, which is for 2mm flat coping only

Fabrication: Made to order -- non-returnable unless faulty

Country of Manufacture: United Kingdom (Chelmsford, Essex)

Calculating the Width Size: The 3mm Flat Coping Formula

The 23 sizes from 510mm to 1060mm refer to the WIDTH of the coping profile, not the run length. Every section on this page is 2m long. The formula for the 75mm external leg flat coping system is straightforward because both legs are equal:

• Measure the parapet wall width at the top from outside face to inside face.

• Add 75mm (external leg) + 75mm (internal leg) + 10mm + 10mm (returns) = 170mm.

• Total: wall width + 170mm = the size to order. A 340mm wide commercial parapet gives 510mm, the smallest available size. A 440mm wall gives 610mm. A 565mm wall gives 735mm.

• Important: this formula is different from the sloping coping formula. Sloping coping with a 100mm external leg uses wall width + 195mm. Flat coping with 75mm equal legs uses wall width + 170mm. Apply the correct formula for the product you are ordering.

• If the calculated size falls below 510mm, the parapet is likely in the domestic 2mm system range. Verify the specification before ordering.

• If the result falls between two sizes, order the next size up.

• On site: measure across the top of an installed section from external leg tip to internal leg tip. That measurement is the size.

How Many 2m Sections Do You Need?

On a commercial parapet, plan each face separately. Work out the total linear metres of each straight face, then choose the most efficient length combination.

• 4m face: two 2m sections, one joint, no waste. The most efficient use of the 2m section.

• 5m face: two 2m sections plus a 1m cut or a separate 1m section. Two lengths, one joint.

• 6m face: three 2m sections with two joints, or two 3m sections with one joint. The 3m sections are more efficient on a 6m face.

• 7m face: one 3m section plus two 2m sections with two joints. More efficient than three 2m sections plus a 1m infill.

• Multiple faces: add up 2m section requirements per face. Corner pieces and stopends do not contribute to run length calculations.

For faces of 3m or more, the 3m length is the more efficient primary section. Use 2m sections for medium faces of 2m to 5m and for infill positions. Use the 1m length for short faces and final infill pieces where the remaining length is under 2m.

How to Install 3mm Flat Coping 2m Sections

Mark the bracket positions along the full run before fixing anything. Fix the 5mm aluminium coping brackets at the correct centres, not exceeding 1000mm, with brackets within 150-200mm of every run terminal, corner junction and stopend position. A 2m section needs a minimum of three brackets: one near each end and at least one intermediate. On exposed sites or elevated commercial buildings, reduce bracket centres to 750mm or as specified by the structural engineer. Confirm all brackets are flat to the wall top before pressing any coping.

Press the 2m flat coping sections onto the brackets from the fixed terminal end of the run. Apply a continuous bead of colour coded sealant in the matching RAL to the internal face of each joint before butting the next section. The sealant bead is the primary weathertight seal at every joint. Keep it continuous.

Lock the coping to the brackets using colour coded metal fasteners in the matching RAL. Fit the appropriate 3mm 90 degree corner pieces at every change of direction and the 3mm closed stopends at every run terminal. Apply a finishing sealant bead on all external joint faces.

Where the 3mm 2m Flat Coping Section Is Used

Commercial Buildings with Medium Parapet Faces

On commercial buildings where the perimeter parapet includes faces between 2m and 5m, the 2m section is the natural fit. An office building with a plant room enclosure at 4m wide, a retail unit with a service yard access side parapet of 3.5m, or a stepped parapet detail on a mixed-use development all produce medium-length faces that the 2m section serves well. Used alongside the 3m primary lengths for the longer continuous runs, the 2m section handles the geometry of a real commercial building more efficiently than trying to plan everything in 3m increments. The aluminium coping case study shows a completed commercial coping installation on a live UK project.

New-Build Housing Developments with 3mm Specification

On NHBC-registered residential developments where the house type specification calls for 3mm flat coping on parapet walls, the 2m section handles medium parapet faces within each plot. Volume housebuilders ordering the full system across a development phase, including 5mm brackets, corners and stopends from the same Chelmsford manufacturer, get colour-matched components and a traceable single-source specification. The aluminium coping case study from London demonstrates the flat coping system at residential project scale.

Exposed Site Parapets Requiring 3mm Specification

On buildings near the Essex or Kent coast, on hilltop or open-aspect sites, or on any building where the wind loading at parapet level has been assessed and 3mm specified, the 2m flat coping section is the correct infill length within a predominantly 3m installation. Get the 5mm bracket centres right for the site exposure, seal every joint with colour coded sealant, and the 3mm flat coping will perform without attention for the life of the building.

Commercial Refurbishment: Like-for-Like Replacement

When replacing existing 3mm flat coping on a commercial building, the replacement must be 3mm. A 2mm replacement on a 3mm installation produces a visible mismatch and is under-specified for the site conditions that originally required 3mm. The 2m section is the right replacement length for medium parapet faces, alongside the matching 3mm 90 degree corners, closed stopends and 5mm brackets from the same Chelmsford manufacturer.

Frequently Asked Questions

When should I use 3mm flat coping rather than 2mm?

Use 3mm when the project is commercial, when the parapet wall width produces a coping girth of 510mm or above, when the NHBC or structural specification requires 3mm, or when the site is exposed or the building is at two or more storeys. For domestic flat roof extensions, garages and boundary walls in sheltered settings, the 2mm flat coping system is normally the right choice.

What is the difference between flat and sloping aluminium coping?

Flat coping has a level top surface that sits horizontally on the parapet. Sloping coping has a built-in slope that tilts toward the external face, actively draining rainwater off the surface. Flat coping is standard on commercial buildings and contemporary architecture where a horizontal parapet profile is specified. Sloping coping is common on residential extensions and new-build housing where positive surface drainage is preferred. The profiles, corners and stopends are not interchangeable between the two systems. For sloping coping in 3mm gauge, see the 3mm sloping coping 2m length.

What size do I need for my commercial parapet?

Wall width + 170mm = the size to order for the 75mm external leg flat coping system. A 340mm wide commercial parapet gives 510mm, the smallest available size. A 440mm wall gives 610mm. A 565mm wall gives 735mm. The 23 sizes refer to coping widths, not run lengths. Every section on this page is 2m long regardless of the size selected.

What bracket do I use with 3mm flat coping?

The 5mm aluminium coping bracket is the correct bracket for all 3mm flat coping. The 4mm bracket is for 2mm flat coping only. Fix at maximum 1000mm centres with a bracket within 150-200mm of every run end, corner and stopend. For a 2m section, you need a minimum of three brackets. On exposed sites or elevated buildings, reduce to 750mm centres or follow the structural engineer's specification.

Can I mix 3mm and 2mm components on the same flat coping installation?

No. The 2mm and 3mm flat coping profiles have different wall thicknesses. A 2mm corner or stopend on a 3mm run will not produce a flush junction. All components on a 3mm installation must be 3mm gauge throughout: lengths, corners, stopends and upstand stopends. Only the bracket differs by name (5mm for 3mm coping, 4mm for 2mm coping); the profile accessories are system-specific.

How many 2m sections do I need for my project?

Plan each parapet face separately. For faces of 4m to 5m, two 2m sections give the most efficient result with one joint. For faces of 2m to 4m, one 2m section covers the face with a short cut or a 1m infill piece. For faces over 5m, a 3m primary section with a 2m or 1m infill usually gives a lower joint count. Add up the 2m section requirements across all faces and order accordingly.

Part of a Complete 3mm Flat Coping System | 75mm External Leg

This 2m section is one of three run lengths in the 3mm aluminium flat coping system with a 75mm external leg. A complete installation needs lengths in the right mix, 3mm corner pieces at every change of direction, 3mm stopends at every run terminal, 5mm brackets at the correct centres, sealant at every joint, and metal fasteners on commercial substrates. Order all components from the same Chelmsford manufacturer for matching profiles, consistent colour and a system that fits together. The full 3mm flat coping system with 75mm external leg includes:

• 3mm Aluminium Flat Coping - 1m Length | 75mm External Leg

• 3mm Aluminium Flat Coping - 2m Length | 75mm External Leg (this product)

• 3mm Aluminium Flat Coping - 3m Length | 75mm External Leg

• 3mm Aluminium Flat Coping - 90 Degree Corner | 75mm External Leg

• 3mm Aluminium Flat Coping - 135 Degree Corner | 75mm External Leg

• 3mm Aluminium Flat Coping - Closed Stopend | 75mm External Leg

• 3mm Aluminium Flat Coping - Stopend Upstand | 75mm External Leg

• 3mm Aluminium Flat Coping - 90 Degree T-Junction | 75mm External Leg

• 5mm Aluminium Coping Bracket

• Colour Coded Sealant 300ml

• Colour Coded Fasteners (Metal)

For the full 3mm flat coping range and the 2mm flat coping system, visit the Aluminium Flat Copings collection page. For 3mm flat coping delivered as an alternative profile to sloping coping, the 3mm sloping coping 2m length is the equivalent product in the sloping profile.

Standards and Compliance

Aluminium flat coping on commercial flat roof parapets in the UK is specified under BS 6229:2018 - Flat Roofs with Continuously Supported Flexible Waterproof Coverings. The standard covers parapet and edge detailing for flat roofs, including coping specification, joint treatment and fixing requirements. A 3mm aluminium flat coping system with 5mm brackets at the correct centres, sealant-bedded joints and correctly specified accessories throughout is consistent with the weathertight parapet requirements of this standard.

The external grade polyester powder coat applied to all 3mm flat coping components from Online Metal Store Ltd meets the requirements of BS EN 12206-1 - Organic Coatings on Aluminium and Aluminium Alloys. On a commercial project where the coping specification forms part of a contract document, this standard provides a documented performance basis for the coating across every component in the system.

For NHBC-registered new-build projects, Chapter 7.1 of the NHBC Standards covers parapet wall and flat roof construction. A 3mm aluminium flat coping system, correctly sized and installed with 5mm brackets and sealant-bedded joints, is consistent with the parapet detailing requirements for new-build completions where 3mm flat coping is the specified configuration.