3mm Aluminium Flat Coping – Closed Stopend | 75mm External Leg
3mm Aluminium Flat Coping – Closed Stopend | 75mm External Leg
On a commercial flat roof parapet, every component in the coping system is under scrutiny. The specifier, the contractor and the facilities manager all have an interest in a system that performs without intervention for at least 25 years. The straight 3mm flat coping lengths and the 90 degree corners carry the main weathertight load across the parapet, but the stopend is where the system either closes out properly or leaves a gap. An open or poorly fitted coping termination on a commercial building with an inaccessible or difficult-to-maintain parapet is a liability: water gets in through the end of the coping run, tracks down the wall, and does not show up as a damp problem until the finishes inside are already compromised.
This 3mm aluminium flat coping closed stopend terminates the end of a 3mm flat coping run with a sealed, weathertight closure in the correct gauge for commercial and exposed-site specification. Available in 29 sizes from 185mm to 885mm and powder coated in any RAL colour, it is the terminal component that completes a 3mm flat coping system at every open run end. Manufactured in Chelmsford, Essex, it matches the profile and finish of all other components in the 3mm flat coping range.
Product Overview
The closed stopend caps the open end of a flat coping run with a fully sealed end face. The profile wraps over the top of the parapet wall and closes off the coping at the termination point on all three sides, with no open edge and no gap for water to enter. It is the correct terminal piece for the 3mm aluminium flat coping system with a 75mm external leg, and it works alongside the 3mm flat coping 135 degree corner, the 3mm closed stopend upstand, and the 3mm T-junction as part of a complete perimeter coping system.
This product is the 3mm gauge version of the coping stopend. It is available in the same 29 sizes as the 2mm closed stopend, covering parapet wall widths from approximately 15mm up to around 715mm depending on wall construction. The 3mm gauge is the correct specification for commercial projects, NHBC new-build schemes, and any site where the structural or architectural specification calls for a heavier gauge coping system. All components are powder coated to any RAL colour using an external grade polyester finish, fabricated to order at the Chelmsford facility, and non-returnable as made-to-order items.
Key Benefits
Heavier Gauge for Commercial and Exposed-Site Durability
At 3mm, this stopend has greater rigidity than the 2mm equivalent, which matters on a commercial parapet where the end detail is exposed to full wind pressure without the sheltering effect that a suburban domestic setting often provides. A stiffer end piece maintains its profile under repeated thermal cycling and wind loading over a longer service life. On a building that will not be re-roofed for 30 years or more, the marginal cost difference between 2mm and 3mm is negligible compared to the cost of remedial work on a failed end detail.
Sealed End Face with No Exposed Joints
The closed stopend is fabricated as a single pre-formed piece that wraps over the end of the coping profile and seals the end face completely. Once fitted and sealed with sealant at the joint to the straight length, there is no open edge, no exposed aluminium section, and no gap at the coping termination. On a 3mm commercial coping system where the full perimeter may be 50 metres or more, having a properly sealed end at every run termination is part of the overall weathertight strategy for the parapet.
29 Sizes to Match Any Commercial Wall Width
Commercial parapets come in a wide range of wall widths depending on the building construction, insulation thickness and parapet design. The 29 sizes available, from 185mm to 885mm in 25mm increments, cover virtually every wall width you will encounter on a UK commercial flat roof project. The size selection guide below explains how to calculate the correct stopend size from the overall coping girth measurement.
Consistent Colour Across the Full 3mm System
On a commercial project, the coping colour is typically specified by the architect and forms part of the contract documents. Every component in the order, including this stopend, the straight lengths, the corners and the brackets, is powder coated in the same RAL colour in the same batch at the Chelmsford facility. There are no colour matching tolerances to worry about between components from different batches or different manufacturers. The system arrives as a matched set.
UK Manufactured for Programme Certainty
Made-to-order at the Online Metal Store Ltd facility in Chelmsford, Essex, with UK manufacturing lead times rather than overseas shipping delays. For a commercial programme where the coping installation sits on the critical path to watertight, having the stopends arrive on time from a UK manufacturer is more reliable than sourcing from a European supplier with variable shipping timescales. The full 3mm flat coping system can be ordered as a package from a single source.
Technical Specifications
Material: 3mm grade aluminium
Profile: Flat coping closed stopend
External Leg: 75mm
Available Sizes: 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)
Finish: Polyester powder coating, external grade
Colour: Any RAL colour to order
Type: Closed (fully sealed end face)
Compatible System: 3mm Aluminium Flat Coping range | 75mm External Leg
Recommended Bracket: 5mm Aluminium Coping Bracket (correct specification for 3mm coping system)
Fabrication: Made to order - non-returnable unless faulty
Country of Manufacture: United Kingdom (Chelmsford, Essex)
How to Measure for the Right Stopend Size
The stopend size must match the overall width of the coping profile, not the wall width alone. The calculation for a 75mm external leg flat coping with standard 10mm returns is:
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Measure the top width of the parapet wall from outside face to inside face. This is the wall width.
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Add 150mm for both external legs (75mm + 75mm).
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Add 20mm for both returns (10mm + 10mm).
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Total: wall width + 170mm = your stopend size. For example, a 265mm wide parapet wall gives a coping girth of 435mm. Order the 435mm stopend.
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If your calculated girth falls between two available sizes, always select the next size up. A stopend that is fractionally oversized can be trimmed on site; one that is undersized will not close the profile correctly.
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Quickest method on site: measure the overall width of the installed coping profile directly across the top surface, including both legs. That measurement is the stopend size to order.
Closed Stopend or Stopend Upstand: Which Does Your Detail Require?
Both components seal the end of a 3mm flat coping run, but the end detail works differently. The closed stopend fully seals the open end face of the coping, with no opening at the termination. It is correct wherever the coping run ends at a wall termination, an abutment with a building face, or a corner where the run is simply capped off. The 3mm stopend upstand has an upstand element at the end that allows the coping to terminate against a rising element, such as a structural post, an upstand penetration, or a detail where water needs to drain over the end of the run rather than being fully closed off.
On most commercial flat roof parapets, the closed stopend is the correct terminal piece at both ends of every straight coping run. Use the upstand version only where the architectural or structural detail specifically requires it. If you are unsure which applies to a specific detail on your project, raise it with the specifier before ordering, as both are custom-fabricated and non-returnable.
How to Fit a 3mm Flat Coping Closed Stopend
Fix the 5mm aluminium coping brackets along the full run first, with a bracket positioned near each end to give the stopend solid bearing. On a 3mm commercial coping system, bracket positions should follow the structural engineer's recommendation where wind uplift calculations have been carried out for the site. The end bracket should be set back from the wall termination far enough that the stopend seats fully over the end of the final straight length without the bracket fouling the inside of the stopend profile.
Offer the stopend to the open end of the final straight length and check the fit before sealing. The stopend should slide over the coping end and sit flush with the outer face of the straight length on all sides. Apply a continuous bead of colour coded sealant around the full internal perimeter of the stopend before pressing it to its final position. On a commercial parapet, do not reduce the sealant application at the stopend. The joint between the stopend and the straight length is a point of potential water ingress, and the sealant bead is the only thing sealing it. A thin or incomplete bead at the end of a 50-metre coping run will be the point of failure.
Secure the assembly using colour coded metal fasteners in the matching RAL colour. On a commercial project with a metal deck, steel kerb, or structural steel curb at the parapet, use the metal fasteners rather than timber fixings. Fix through the bracket bearing positions, keeping fixings in alignment with the bracket below for proper load transfer. Apply a neat finishing bead of sealant on the external joint line between the stopend and the straight length.
Where the 3mm Flat Coping Closed Stopend Is Used
Commercial Flat Roof Parapets
Commercial buildings, including office developments, retail parks, logistics units and mixed-use schemes across the South East and the wider UK, typically specify 3mm aluminium flat coping for the parapet system. On a commercial parapet, every component in the system is specified to the same gauge and finish, and the stopends are ordered alongside the lengths, corners and 5mm coping brackets as part of the full package. Ordering the stopends from the same Chelmsford manufacturer as the rest of the system means the colour and profile will match exactly, and there is a single point of contact for the full coping supply. The aluminium coping case study shows the full 3mm system in use on a live UK commercial project.
New-Build Housing Developments with NHBC Registration
Volume housebuilders on NHBC-registered developments across Essex, the Home Counties and the wider South East commonly specify 3mm aluminium coping for flat roof parapet details on house types that include flat-roofed elements. Whether the application is a garage block, a covered walkway, an amenity building or a parapet on a terrace unit, the 3mm system is the specification that supports the NHBC warranty position. The closed stopend is ordered as part of the full 3mm flat coping system alongside the lengths, corners and upstands for each house type, typically as a package order for each phase of the development.
Exposed and Coastal Sites
For flat roof parapets on buildings within a few kilometres of the Essex, Suffolk or Kent coastlines, or on open-aspect sites exposed to prevailing south-westerly winds, the 3mm gauge is the appropriate coping specification. The heavier gauge provides greater resistance to the wind uplift forces that an exposed parapet experiences, and the fully sealed closed stopend is particularly important on these sites: a poorly sealed end detail on an exposed coastal building will fail faster than almost anywhere else. Sites in Southend-on-Sea, Mersea Island, Clacton and along the Thames Estuary warrant the 3mm system as standard. Use the colour coded sealant at every joint without exception on exposed-site installations.
Schools, Healthcare and Public Sector Buildings
Schools, GP surgeries, dental practices, care homes and other public sector buildings typically carry a long-term asset management requirement. The facilities team or asset manager expects the coping system to remain maintenance-free for a defined period, usually 25 years or more, and the specification reflects that. The 3mm closed stopend, as part of a complete 3mm flat coping system from a single UK manufacturer, gives the client a traceable specification, consistent colour across the full perimeter, and a documented powder coat standard that supports long-term warranty and maintenance planning.
Frequently Asked Questions
When should I use the 3mm stopend instead of the 2mm?
Use the 3mm stopend whenever you are using 3mm flat coping lengths on the project. The stopend gauge must match the coping gauge. Beyond that, choose 3mm for commercial projects, NHBC-registered new builds, exposed or coastal sites, taller buildings with higher parapets, and any project where the specification document calls for 3mm. For straightforward domestic rear extensions and outbuildings in sheltered locations, 2mm is usually the appropriate choice. The 2mm and 3mm stopends are the same profile and the same size range; the difference is the material thickness and the corresponding stiffness and wind resistance.
How do I calculate the correct stopend size for a 3mm coping system?
The calculation is the same for 3mm as for 2mm: measure the wall width at the top of the parapet and add 170mm to account for both 75mm external legs and both 10mm returns (75 + 75 + 10 + 10 = 170). A 265mm wide wall gives a stopend size of 435mm. A 390mm wide wall gives 560mm. Select the exact size from the available 29 options (185mm to 885mm in 25mm steps). If your figure falls between two sizes, order the next size up. The quickest method on site is to measure the overall width of the installed coping profile across the top: that measurement is the stopend size.
Is this stopend compatible with the 2mm flat coping lengths?
No. The 3mm stopend is designed for the 3mm flat coping system. Although the overall profile shape is the same as the 2mm version, the wall thickness is different, which means the fit at the junction between a 3mm stopend and a 2mm straight length will not be correct. Always match the stopend gauge to the gauge of the straight lengths it terminates. If you are using 2mm lengths, order the 2mm closed stopend. If you are using 3mm lengths, use this 3mm version.
Does this product need a specific bracket?
Yes. For a 3mm aluminium flat coping system, the 5mm aluminium coping bracket is the correct specification. The 5mm bracket is heavier and provides greater fixing resistance than the 4mm bracket, which is appropriate for the heavier gauge coping and the more demanding sites where 3mm is typically specified. On exposed sites or tall buildings where wind uplift calculations are required, the bracket spacing should be confirmed with the structural engineer. Do not use the 4mm bracket as a substitute on a commercial or exposed-site 3mm coping installation.
What is the difference between the closed stopend and the stopend upstand on this system?
The closed stopend seals the end face of the coping run completely with no opening. It is the standard terminal piece for most flat coping run terminations: wherever the coping simply ends at a wall edge, a corner, or an abutment with a building face. The stopend upstand has an upstand element at the end that allows the coping to terminate against a rising detail or allows water to drain over the end of the run. On the majority of commercial flat roof parapets, the closed stopend is correct at most or all terminations. The upstand is a specific detail for specific conditions. If the architectural drawings do not specify an upstand at a particular end, use the closed stopend.
Part of a Complete 3mm Flat Coping System
This stopend is one component in the complete 3mm aluminium flat coping system with a 75mm external leg. On a commercial project, all components should be ordered from the same manufacturer to guarantee matching profiles, consistent powder coat colour across the full perimeter, and a single-source system with a clear specification. The full 3mm flat coping system with 75mm external leg includes:
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3mm Aluminium Flat Coping 90 Degree Corner | 75mm External Leg
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3mm Aluminium Flat Coping 135 Degree Corner | 75mm External Leg
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3mm Aluminium Flat Coping - Closed Stopend | 75mm External Leg (this product)
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3mm Aluminium Flat Coping - Stopend Upstand | 75mm External Leg
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3mm Aluminium Flat Coping - 90 Degree T-Junction | 75mm External Leg
For the full range overview across both 2mm and 3mm gauges, visit the Aluminium Flat Copings collection page. If the project calls for 2mm coping, the 2mm flat coping closed stopend is the equivalent terminal piece for the lighter gauge system.
Standards and Compliance
Aluminium flat coping systems on UK flat roof parapets are specified and detailed under BS 6229:2018 - Flat Roofs with Continuously Supported Flexible Waterproof Coverings. This standard covers parapet and edge detailing for flat roofs in the UK, including the requirements for coping system terminations. A 3mm aluminium flat coping system with properly fitted and sealed closed stopends at every run termination is consistent with the edge protection and weathertightness requirements set out in the standard.
The external grade polyester powder coat finish applied to all Online Metal Store Ltd aluminium flat coping components, including this 3mm closed stopend, 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 or long-term asset management plan, having a documented coating standard across every component in the system is part of the specification compliance requirement.
For NHBC-registered new-build projects, Chapter 7.1 of the NHBC Standards covers flat roof and parapet wall construction requirements. A 3mm aluminium flat coping system with correctly specified and installed stopends supports the NHBC warranty position and is consistent with the parapet detailing requirements for new-build completions across all housing types.