2mm Aluminium Sloping Coping – 1m Length | 125mm External Leg - Online Metal Store Ltd

2mm Aluminium Sloping Coping – 1m Length | 125mm External Leg

£34.70
(£41.64 Inc VAT)

2mm Aluminium Sloping Coping – 1m Length | 125mm External Leg

The difference between a 100mm and a 125mm external leg on aluminium sloping coping is 25mm of overhang. That is not a large number in absolute terms, but on a parapet wall it matters in three ways: the coping profile looks proportionally right against the wall width, water is thrown further clear of the wall face below, and on a new-build cavity wall parapet or an insulated parapet construction, the 125mm leg is frequently the specification rather than an upgrade. If you have arrived here because your wall width produces a coping girth that does not sit in the size range for the 100mm system, or because the project spec calls for a 125mm leg, this is the product for your 2mm sloping coping installation.

This is the 2mm aluminium sloping coping in a 1m length with a 125mm external leg. It carries the same built-in slope and the same 29 available width sizes as the 100mm external leg 1m version, with the profile widened by 25mm on the external leg to suit wider wall constructions and more prominent overhang specifications. Manufactured in Chelmsford, Essex, powder coated in any RAL colour, and available in 1m, 2m and 3m lengths across the same width size range.

100mm or 125mm External Leg: The Selection Guide

Both leg sizes are available across the full 2mm sloping coping range at Online Metal Store Ltd. The profile, slope angle, gauge and installation method are identical. The difference is in the overhang depth. Here is how to choose between them:

Wall Width and Visual Proportion

The external leg should overhang the outside face of the parapet wall by enough to carry water clear and to look proportionally scaled against the wall. As a general principle, an external leg of around 30% of the total wall width gives a balanced, well-scaled profile. On a 100mm single-skin parapet wall, a 100mm external leg is appropriate. On a 150mm to 200mm cavity wall or insulated parapet, a 125mm external leg gives a better visual and functional result. Hold a 125mm coping length against the wall before committing to an order: if the 100mm leg looks narrow against the parapet width, the 125mm is the right call.

Project and Housebuilder Specification

Many housebuilders and architects specify a minimum external leg for sloping coping. A 125mm minimum overhang is common on new-build housing across the South East and the Home Counties, particularly on cavity wall construction where the parapet wall thickness regularly exceeds 150mm. If the project has a written coping specification, check the external leg dimension before ordering. The 125mm leg is the standard for a significant proportion of new-build house type specifications across Essex and the wider South East.

Extended Water Throw-Off Distance

A 125mm external leg discharges rainwater 25mm further from the wall face than a 100mm leg. On a rendered or painted external wall finish below the parapet, this matters over a 20 to 30 year service life. Water running back close to the wall face leaves mineral staining, accelerates surface deterioration and can cause efflorescence on masonry beneath the drip line. The 125mm overhang pushes the discharge point further out, reducing these effects on exposed or south-west-facing elevations where driving rain is more frequent.

Sizing Formula Difference

Because the external leg is 25mm wider, the formula for calculating coping width size is different from the 100mm system. The 125mm system uses wall width + 220mm (100mm leg gives wall width + 195mm). This means for the same parapet wall, you need a wider size from this system than from the 100mm system. The size calculation section below explains this in full. Do not use the 100mm formula for a 125mm installation: you will order a coping 25mm too narrow.

Product Overview

This 1m length is part of the Online Metal Store Ltd 2mm aluminium sloping coping range with a 125mm external leg, manufactured at the Chelmsford facility. The 125mm external leg provides the wider overhang, and the 75mm internal leg returns down the inside face of the parapet. The slope across the top surface tilts the profile outward so rainwater drains toward the external face. The 29 available width sizes from 185mm to 885mm in 25mm increments cover domestic and wider parapet wall constructions suited to the 125mm external leg specification. All components in this system, lengths, corners, stopends and brackets, are available from the same range and are powder coated in any RAL colour.

The 1m length serves the same three functions in this system as in the 100mm system: infill at the end of a longer run, single-piece installation on short parapet sections, and tight-access positions where a longer length is difficult to handle. The 2m length and 3m length in the same 125mm system cover longer straight runs. All three lengths share the same system accessories, brackets, sealant and colour range.

Key Benefits

125mm Overhang for Wider Walls and Better Water Clearance

The 125mm external leg extends 25mm further beyond the wall face than the 100mm equivalent, giving a wider drip detail that carries water further clear of the wall below. On a cavity wall parapet construction, or a wall with a rendered or fair-faced finish that benefits from maximum distance between the drip point and the surface, the 125mm leg is the correct choice. The wider overhang also produces a more substantial visual profile at parapet level, which suits the wider wall widths this leg size is designed for.

Built-In Slope for Active Surface Drainage

The sloped top surface tilts toward the external face, directing rainwater off the coping and over the drip edge rather than allowing it to pond on the surface. On a 125mm external leg system, the combination of the wider drip detail and the active slope provides efficient drainage across a wider profile. This is particularly relevant on south-west-facing parapets across the South East where the prevailing weather comes in off the Atlantic and sustained driving rain is a regular winter condition.

Powder Coated in Any RAL Colour

The finish on every component in the 125mm sloping coping range is an external grade polyester powder coat available in any RAL colour. These products are not anodised. The current product page contains incorrect references to an anodising process and an anodising finish: these statements are factually wrong and must be removed. Powder coating is the only finish applied to these products. Specifying a RAL colour at the time of order gives a consistent powder coated finish, with a colour-matched result across every component in the order when lengths, corners, stopends and brackets are ordered together.

Concealed Bracket Fixing, Clean Installed Line

The 125mm sloping coping system uses the same concealed bracket fixing approach as the 100mm system. The 4mm aluminium coping bracket is fixed to the wall top before the coping is installed, and the coping profile presses down onto the bracket from above. No fastener penetrates the coping face or top surface. The result is a clean, unbroken installed line with no visible hardware, suited to both new-build projects where the parapet is a designed architectural element and refurbishment work where a neat finish is required.

Made to Order in Chelmsford, Fast UK Delivery

Each length is fabricated to the width size and RAL colour specified at the Online Metal Store Ltd facility in Chelmsford, Essex. As with all components in the sloping coping range, this is a custom-fabricated, non-returnable item. Measuring the wall width correctly and applying the correct 125mm sizing formula before ordering is essential. UK manufacturing keeps lead times short across Essex, the South East and the wider UK.

Technical Specifications

Material: 2mm grade aluminium

Profile: Sloping coping length

Length: 1m (1000mm)

External Leg: 125mm

Internal Leg: 75mm

Width Sizes Available: 185mm, 210mm, 235mm, 260mm, 285mm, 310mm, 335mm, 360mm, 385mm, 410mm, 435mm, 460mm, 485mm, 510mm, 535mm, 560mm, 585mm, 610mm, 635mm, 660mm, 685mm, 710mm, 735mm, 760mm, 785mm, 810mm, 835mm, 860mm, 885mm (29 sizes in 25mm increments)

Size Note: The "size" refers to the overall WIDTH of the coping profile, NOT the run length. All lengths are 1m; the size determines girth to fit wall width. Use formula: wall width + 220mm = size to order.

Sizing Formula: Wall width + 125mm (external leg) + 75mm (internal leg) + 10mm + 10mm (returns) = wall width + 220mm

Finish: Polyester powder coating, external grade, NOT anodised

Colour: Any RAL colour to order

Compatible Bracket: 4mm Aluminium Coping Bracket (2mm coping system)

Fabrication: Made to order - non-returnable unless faulty

Country of Manufacture: United Kingdom (Chelmsford, Essex)

Calculating Your Coping Width Size: The 125mm Formula

This is the most important step before ordering. The 29 sizes from 185mm to 885mm on this page refer to the overall WIDTH of the coping profile, not the run length, all lengths on this page are 1m. The size you select must match the overall girth of your parapet wall. The formula for the 125mm external leg system is different from the 100mm system and gives results 25mm wider for the same wall:

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

  • Add the external leg (125mm) and the internal leg (75mm) = 200mm.

  • Add both 10mm returns = 20mm.

  • Total: wall width + 220mm = the size to order. A 165mm wide parapet wall gives 165 + 220 = 385mm. A 240mm wall gives 240 + 220 = 460mm.

  • Important: this formula gives results 25mm larger than the 100mm system formula (wall width + 195mm). If you have used the 100mm formula on a previous order, do not apply it here. A 165mm wall needs the 385mm size on the 125mm system, but only the 360mm size on the 100mm system.

  • If the result falls between two available sizes, select the next size up. On a custom-fabricated non-returnable product, slightly oversized is always preferable to undersized.

  • Quickest site check: measure the overall width of an installed length from this system directly across the top surface. That measurement is the size to order.

1m, 2m or 3m Length: Which to Order

The 125mm system is available in all three lengths. The selection logic is the same as for the 100mm system: the 3m length is the most efficient choice for long continuous runs; the 2m length covers medium runs and infill sections; the 1m length handles short parapet sections, final infill pieces, and tight-access installations. A full worked guide to length selection is on the 100mm 1m sloping coping page, and the same principles apply here. The key rule: plan the run with 3m lengths first, work down to 2m and 1m for infill, and never order more 1m sections than the run layout requires, as each additional 1m section adds a joint that the longer lengths avoid.

How to Install 125mm Sloping Coping Lengths

Set out the bracket positions along the parapet run before fixing. Fix the 4mm aluminium coping brackets at the correct centres not exceeding 1000mm with a bracket within 150-200mm of every run terminal, corner junction and stopend position. For a 1m length, you need a minimum of two brackets. Confirm that all brackets are flat to the wall top and aligned before pressing any coping into place.

Press coping lengths onto the brackets working from the fixed terminal end of the run. Before butting each length up to the previous one, apply a continuous bead of colour coded sealant in the matching RAL colour to the internal face of the joint. The sealant at each joint is the primary weathertight line between adjacent lengths. On an exposed elevation with a 125mm external leg profile, the wider overhang means the joint between lengths is more exposed to driven rain from the side; a complete sealant bead at every joint is non-negotiable.

Lock the coping to the brackets using colour coded fasteners in the matching RAL colour. Fit the left and right handed closed stopends for the 125mm system at the terminal ends, and the appropriate corner pieces at every change of direction. Apply a neat finishing sealant bead on all external joint faces.

Where the 125mm 1m Sloping Coping Length Is Used

New-Build Housing with Cavity Wall Parapets

Volume housebuilders on NHBC-registered developments across Essex, the Home Counties and the wider South East commonly specify 125mm external leg sloping coping for house types with cavity wall parapets. On a development where the same house type repeats across 20 to 100 plots, 1m sections are frequently ordered alongside the 3m lengths to handle infill sections where the parapet run does not divide neatly into 3m increments. The aluminium sloped coping case study demonstrates the 125mm sloping coping system installed at development scale across multiple residential units.

Infill Sections on Wider Parapet Runs

On a longer parapet installation where the overall run includes sections that do not divide into whole 3m or 2m lengths, the 1m section fills the gap. On a 7.8m parapet in the 125mm system, two 3m lengths and one 1.8m infill cut from a 2m length accounts for most of the run; a short return or a complex corner detail may need a 1m section for the final piece. Ordering the 1m length and cutting to the precise measurement on site is more economical than ordering an additional 3m length and cutting 1.2m of waste from a made-to-order non-returnable product.

Prominent Parapets and Architectural Projects

On residential and commercial projects where the parapet coping is a visible architectural element on the front elevation of a new-build house, on a roof terrace parapet visible from the street, or on a contemporary extension on a prominent corner plot, the 125mm external leg gives a more deliberate, scaled presence than the 100mm version. The wider overhang casts a stronger shadow line below the parapet, which reads clearly from street level on a well-proportioned building. For architects and developers specifying coping on projects where the parapet detail contributes to the streetscape, the 125mm system, including this 1m section for infill and short runs, is the specification that delivers the intended visual result. The full aluminium sloping coping range is available from the same Chelmsford manufacturer.

Replacement Coping on Existing 125mm Systems

When replacing failed or degraded coping on an existing building where the original system used a 125mm external leg, the replacement must match that leg dimension. Mixing leg sizes within a single installed system produces a visible mismatch in profile width and overhang that is immediately apparent from ground level. For refurbishment projects on domestic and residential buildings across Essex and the South East, the left and right handed stopends, corners, and lengths for the 125mm system should all be ordered from the same Chelmsford source to ensure consistent profile and colour.

Frequently Asked Questions

What is the difference between the 100mm and 125mm external leg sloping coping?

Both systems use the same 2mm aluminium gauge, the same slope angle and the same installation method. The 125mm external leg projects 25mm further beyond the wall face than the 100mm, giving a wider overhang, throwing water further clear, and producing a wider visual profile on the finished parapet. The 125mm system is better suited to cavity wall constructions, wider parapets, and projects where the housebuilder or architect specification calls for a minimum 125mm leg. The sizing formula also differs: the 125mm system uses wall width + 220mm, while the 100mm system uses wall width + 195mm.

How do I calculate the correct size for the 125mm system?

Add wall width + 220mm. That figure accounts for the 125mm external leg, 75mm internal leg, and 10mm returns each side (125 + 75 + 10 + 10 = 220). A 165mm wide parapet wall gives 385mm. A 240mm wall gives 460mm. A 315mm wall gives 535mm. If the result falls between two sizes, order the next size up. Do not use the 100mm system formula (wall width + 195mm) for the 125mm system — you will order a coping 25mm too narrow.

The product shows 29 sizes. Are these 29 different run lengths?

No. Every length on this page is 1m long. The 29 sizes from 185mm to 885mm refer to the WIDTH of the coping profile, the overall girth from the external leg tip to the internal leg tip, not the run length. You select the size that matches your wall width using the formula (wall width + 220mm). For example, a 165mm wide wall needs the 385mm size coping, and it will arrive as a 1m section that is 385mm wide and 1000mm long.

When should I use 1m sections rather than 3m?

Use the 1m length as infill at the end of a longer run that does not divide neatly into 3m or 2m sections, as the only length on genuinely short parapet sections (box dormer sides, short garden wall returns), and on tight-access positions where a 3m length is difficult to handle. For long uninterrupted parapet runs, always plan with 3m lengths first. Fewer joints means less sealant, fewer potential failure points, and lower overall material cost.

Is this product powder coated or anodised?

Powder coated only. Every component in the Online Metal Store Ltd 2mm sloping coping range is finished with an external grade polyester powder coating in any RAL colour. These products are not anodised. The current product page contains incorrect references to an anodising process, these are factual errors that do not apply to this product. Powder coating is the only available finish.

Do the 125mm and 100mm system accessories interchangeable?

No. The corner pieces, stopends, upstand stopends and brackets in the 100mm and 125mm systems are separate products with different profile dimensions. A 100mm corner on a 125mm coping run will not produce a flush, correctly aligned junction. Always order all accessories in the leg size that matches your coping lengths. The full suite of 125mm system accessories, including corners, left handed stopends, right handed stopends and upstand stopends, is available from the same Chelmsford manufacturer.

Part of a Complete 2mm Sloping Coping System | 125mm External Leg

This 1m length is one component in the complete 2mm aluminium sloping coping system with a 125mm external leg. Every accessory in this system must match the 125mm leg size. Order all components from the same Chelmsford manufacturer to guarantee matching profiles, consistent powder coat colour, and a system that fits together correctly on site. The full 2mm sloping coping system with 125mm external leg includes:

For the full sloping coping range including the 100mm external leg system and all 3mm variants, visit the Aluminium Sloping Coping collection page. If the 100mm external leg is the right specification for your project, the 100mm external leg 1m length is available from the same Chelmsford range.

Standards and Compliance

Aluminium parapet coping systems in the UK are specified and installed under BS 6229:2018 - Flat Roofs with Continuously Supported Flexible Waterproof Coverings. The standard covers parapet and edge detailing requirements for flat roofs including coping specification, fixings and joint treatment. A properly installed 2mm aluminium sloping coping system with 125mm external leg, using correctly sealant-bedded joints and correctly sized components matched to the wall width, is consistent with the weathertight parapet detailing requirements of this standard.

The external grade polyester powder coat applied to all Online Metal Store Ltd sloping coping components meets the requirements of BS EN 12206-1 - Organic Coatings on Aluminium and Aluminium Alloys. The same coating standard applies across every component in the 125mm system ordered together, providing consistent colour and durability from lengths to corners to stopends.

For NHBC-registered new-build projects, Chapter 7.1 of the NHBC Standards sets out parapet wall and flat roof construction requirements. A 2mm aluminium sloping coping system with 125mm external leg, correctly specified to match the parapet wall width and installed with proper bracket fixing and joint sealing, is consistent with these requirements.

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Custom Fabricated Item

This is a custom-fabricated item made to your selected size and finish. Please double-check measurements before ordering. This product is non-returnable unless faulty, as explained in our Refund & Return Policy

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