2mm Aluminium Sloping Coping – 135° External Corner | 100mm External Leg

The product can be powder coated to suit the project colour schedule, from anthracite grey on modern extensions to bespoke shades for architectural schemes. A matching RAL finish helps the corner blend with coping lengths, flashings, trims and rainwater goods, which is especially important on visible developments where inconsistent colours can make the finished work look pieced together.

Lightweight and Practical on Site

A 2mm aluminium corner gives a strong feel without the handling problems that can come with heavier materials. It is easier to lift, position and adjust on site, which helps when working at roof level or when access is limited on tight domestic streets in places like Southend, Brentwood or East London.

100mm External Leg for Strong Visual Coverage

The 100mm external leg helps cover the face of the wall below the coping line and gives the roof edge a more finished look. It is particularly useful where the external face needs a clean drop over the wall edge, rather than a shallow cover that exposes uneven masonry, render or insulation build-up.

UK Manufactured with Fast Delivery

Because this component is manufactured in Chelmsford, Essex, it supports shorter supply chains for UK projects. That is useful for contractors who need replacement corners, extra fittings or matching parts without waiting on long overseas lead times. It also gives buyers a clearer route if they need advice before ordering.

Technical Specifications

Product name: 2mm Aluminium Sloping Coping 135° External Corner | 100mm External Leg

Material: Aluminium

Thickness: 2mm

Corner type: 135° external corner for sloping coping runs

External leg: 100mm

Profile: Sloping coping corner for angled parapet wall junctions

Finish: Powder coated in any RAL colour

Price shown on current product page: From £57.60 ex VAT, £69.12 inc VAT

Manufacturing location: Chelmsford, Essex, United Kingdom

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

Important measuring note: Confirm the wall width, build-up, overhang requirement and matching sloped coping profile before ordering. The current page clearly states the 100mm external leg, but it should explain how the selected size relates to wall coverage.

Choosing the Right Size / Width / Thickness

Choose the size by measuring the finished parapet width, not just the bare blockwork. Allow for render, waterproofing upstands, insulation build-up and the required overhang. On refurbishment jobs, the finished wall can be very different from the original masonry width, especially on Victorian terraces and older commercial properties.

·         For domestic extensions and garden room parapets, measure after the roof build-up and external finish are confirmed so the selected corner matches the coping lengths on both sides.

·         For commercial flat roofs, check the detail against the roof membrane upstand, insulation zone and external facade finish before choosing the width.

·         For housing developments and care homes, standardise the size across repeated wall details where possible, then order matching corners and straight lengths together.

·         For refurbishments in London, Essex or Kent, allow for older walls that may be uneven, out of square or built up with later render layers.

·         For exposed rooflines, keep the RAL colour consistent across corners, coping lengths, fixings and jointing products so the completed system looks deliberate.

How to Install / How to Fit

Start by dry fitting the corner with the adjacent coping lengths. Check that the 135° angle sits cleanly against the wall junction and that the slope falls in the correct direction. Before fixing, confirm that both adjoining runs line through properly and that the overhang looks even from the external face.

Prepare the substrate so the corner sits flat and stable. Any old loose mortar, failed sealant or high spots should be corrected before installation. Where sealing is required at joints, use a compatible colour coded sealant so the finish does not stand out against the powder coated corner.

Fix the component according to the chosen project detail and the rest of the coping system. If mechanical fixing is required into metal or suitable backing, use the correct colour coded metal fasteners so fixings match the RAL finish and do not distract from the roofline.

Check every joint before leaving site. The corner should sit tight to the connecting coping pieces, with neat sealant lines where required and no open gaps that could collect water. For surrounding details, matching trims, flashings and angles can help keep the roof edge, wall face and waterproofing termination consistent.

Where 135 Degree Aluminium Coping Corners Are Used

Splayed Parapet Walls on Modern Extensions

Many modern extensions use angled walls to soften the layout or follow boundary lines. This product gives the external corner a cleaner finish than a site-made cut, especially when paired with the wider aluminium copings range.

Flat Roofs with Non-Square Perimeters

Flat roofs on schools, retail units, offices and housing blocks are not always simple rectangles. A 135° corner helps continue the coping detail around angled sections while supporting a more reliable roof perimeter. For surrounding waterproofing details, the aluminium roof flashing page can support related specification planning.

Boundary Walls and Raised Terrace Edges

On garden walls, terrace upstands and raised external spaces, angled corners are common where the wall follows a landscaping layout. A powder coated aluminium corner gives a smarter result than leaving exposed masonry vulnerable to staining, frost damage and water tracking.

Housing Developments and Repeat Plot Details

On new-build sites, repeatable components help reduce variation between plots. Ordering the same profile family, finish and accessories makes site work easier and gives the developer a more consistent result. The coping case study can also support trust when buyers want to see practical project use.

Refurbishment Projects with Awkward Existing Angles

Older buildings in places like Colchester, Chelmsford and East London often have wall lines that are not perfectly square. A formed 135° external corner helps manage those angled junctions without relying on improvised cutting, oversized sealant beads or visible patching.

Frequently Asked Questions

What is a 135 degree aluminium coping corner used for?

A 135 degree aluminium coping corner is used where a parapet wall turns at an angled external junction rather than a standard square corner. It connects two sloping coping runs neatly and helps protect the wall below from rainwater, staining and weather damage.

Do I need an external or internal 135 degree corner?

You need an external corner when the wall turns around an outside edge. You need an internal corner when the coping turns into an inside angle. If your layout includes both conditions, order the matching 135 degree internal sloping corner separately so each junction is formed correctly.

Is aluminium better than lead for this type of coping corner?

Aluminium is often better for modern parapet coping because it is lightweight, corrosion resistant and can be powder coated in a wide choice of RAL colours. Lead can still be appropriate on some listed buildings or heritage work where conservation officers require traditional materials, but aluminium is usually the cleaner and easier option for contemporary roof edge detailing.

How do I choose the right size?

Measure the finished wall width, including render, waterproofing, insulation and any other build-up. Then choose the corner size that matches the straight coping lengths being used on both sides of the angle. The size should not be chosen from bare blockwork alone.

Should the joints be sealed?

Most coping junctions need careful joint treatment to stop water entering at the weakest point. Use a suitable colour coded sealant where the detail calls for sealing, and keep the bead neat so the corner still looks professional.

Can this corner be supplied in a specific RAL colour?

Yes. The corner can be powder coated in any RAL colour, which allows it to match straight coping lengths, fixings, trims and other architectural metalwork. This is useful on visible rooflines where colour consistency affects the finished appearance.

Comparison Section

Aluminium Corner Versus Site-Cut Coping Lengths

A purpose-made aluminium corner usually gives a cleaner and more reliable result than cutting two straight lengths on site. Site cuts can work in very simple situations, but they depend heavily on installer accuracy, joint preparation and sealing. A formed corner reduces guesswork and gives the roof edge a more finished appearance.

Aluminium Corner Versus Lead Detailing

Lead still has a place on certain heritage buildings, especially where a conservation officer wants traditional materials retained. For modern flat roofs and commercial parapets, aluminium is often easier to handle, cleaner to colour match and more consistent across a complete coping system.

Aluminium Corner Versus Plastic Wall Capping

Plastic capping can be suitable for lighter garden or budget applications, but it rarely gives the same robust architectural look as powder coated aluminium. For visible buildings, contractor-led projects and exposed roof edges, aluminium gives a more durable and professional finish.

For projects where the corner is only one part of the roof edge, keep the product within a complete aluminium copings specification so the profile, colour and jointing approach stay consistent across the whole run.

Part of a Complete System

This corner works best when it is ordered as part of a complete roof edge system rather than as an isolated fitting. Matching parts reduce colour variation, simplify installation and help the finished roofline look like one designed package.

·         aluminium sloping coping range for the straight runs either side of the corner

·         90 degree sloping coping corner for standard square junctions on the same project

·         135 degree internal sloping corner for inside angled wall returns

·         colour coded sealant for neat joint sealing where required

·         colour coded metal fasteners for visible fixing points where metal backing is used

·         trims, flashings and angles for related roof edge and wall termination details

·         roof accessories for complementary items used around flat roof and parapet work

·         flat 135 degree coping corner if the project uses flat coping rather than a sloping profile

Standards and Compliance

For flat roof and parapet contexts, design teams should consider BS 6229:2025, which covers flat roofs with continuously supported flexible waterproof coverings. The coping corner is not a roof membrane, but its detailing still affects roof edge weathering, water run-off and long-term building protection.

For architectural aluminium finishes, BS EN 12206-1:2021 is the relevant reference for coating aluminium and aluminium alloys using thermosetting coating powder. That supports the product positioning as powder coated aluminium.

For new-build projects, the coping detail should also be considered alongside NHBC warranty expectations, the roof specification and the designer details. Getting this right protects the warranty, the building and the people inside it.