2mm Aluminium Sloping Coping – 90° External Corner | 100mm External Leg
2mm Aluminium Sloping Coping – 90° External Corner | 100mm External Leg
Every right-angle external corner on a sloping coping parapet run needs this piece. The 90° external corner sits at the outside junction where two parapet faces meet at a right angle and the coping profile turns around the corner of the building. It carries the same 100mm external leg and built-in slope as the straight coping lengths in the same system, giving a continuous, flush profile around the full perimeter with no exposed end cuts or filler pieces at the corner position.
Available in the same 29 width sizes as the sloping coping lengths, powder coated in any RAL colour, and fabricated to order at the Online Metal Store Ltd facility in Chelmsford, Essex. One corner piece is required per external right-angle corner on the parapet run.
This corner is part of the 2mm aluminium sloping coping system with a 100mm external leg. It is compatible with the 1m, 2m and 3m coping lengths in the same range and uses the same 4mm aluminium coping bracket as the rest of the system. For the 125mm external leg version of this corner, see the 90° external corner for the 125mm system.
External Corner or Internal Corner: Which Do You Need?
This is the most common question on a coping corner page, and getting it wrong means ordering the wrong product. Here is how to tell them apart:
External Corner (This Product)
An external corner sits at an outside corner of the building, where the parapet wall projects outward and the coping wraps around the corner of the structure. Stand on the ground looking at the building: if the corner sticks toward you, it is an external corner. On a rectangular rear extension, all four corners are external corners. This is the most common corner type on domestic and commercial parapets.
Internal Corner
An internal corner sits at a re-entrant angle, where the parapet forms an inside corner and the coping profile turns inward. These appear on complex building plans, stepped extensions, and any parapet that forms a recessed bay or an L-shaped plan. If the corner angles away from you when you stand looking at the building, it is an internal corner. The 90° internal corner is available from the same 2mm 100mm sloping coping system.
90° vs 135° Corners
Both external and internal corners are available in 90° and 135° versions. A 90° corner fits a parapet wall that meets at a right angle, which covers most rectangular building plans. A 135° corner fits a parapet that meets at an obtuse angle, common on chamfered building corners, bay windows, and contemporary buildings with angled plan forms. If the parapet walls meet at 135° rather than 90°, use the 135° external corner instead of this product.
Key Benefits
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Flush, continuous profile: the corner profile matches the leg dimensions and slope angle of the straight coping lengths exactly. No visible step, gap or filler piece at the corner junction.
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Built-in slope: the slope carries through the corner piece in both directions, maintaining active surface drainage around the external angle and preventing water from sitting at the corner position.
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29 sizes to match your lengths: same 185mm to 885mm size range as the coping lengths. Order the same size as your straight run sections.
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Powder coated in any RAL: colour-matched to the straight sections, stopends and brackets when ordered together in the same RAL at the same time.
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Made to order in Chelmsford: fabricated at the same UK facility as the rest of the system. Non-returnable unless faulty.
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System-compatible: fits directly onto the same 4mm concealed bracket as the straight lengths. No special fixings or additional components required at the corner position.
Technical Specifications
Material: 2mm grade aluminium
Profile: Sloping coping corner
Corner Angle: 90 degrees external
External Leg: 100mm
Internal Leg: 75mm
Width 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)
Size Rule: Order the same size as your straight coping lengths
Sizing Formula: Wall width + 195mm = size to order (same as the coping lengths)
Finish: Polyester powder coating, external grade
Colour: Any RAL colour to order
Compatible Bracket: 4mm Aluminium Coping Bracket
Compatible System: 2mm Aluminium Sloping Coping | 100mm External Leg
Fabrication: Made to order -- non-returnable unless faulty
Country of Origin: United Kingdom (Chelmsford, Essex)
Order the Same Size as Your Coping Lengths
The 29 size options from 185mm to 885mm refer to the overall WIDTH of the coping profile at the corner, from external leg tip to internal leg tip. This is identical to the sizing of the straight coping lengths in the same system. If you have already calculated the correct size for your straight sections using the formula wall width + 195mm, that same size applies here.
If you have not yet calculated your size:
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Measure the parapet wall width at the top from outside face to inside face.
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Add 195mm (100mm external leg + 75mm internal leg + 10mm + 10mm returns).
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The result is the size to order for both the lengths and the corners.
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A 190mm wide wall gives 385mm. A 265mm wall gives 460mm. A 340mm wall gives 535mm.
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If the result falls between two available sizes, select the next size up.
How Many Corner Pieces Do You Need?
Count the number of external right-angle corners on your parapet plan. One corner piece is required per corner, not per linear metre. On a straightforward rectangular parapet, there are four external corners and you need four pieces.
On more complex building plans, count carefully:
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Rectangular parapet (four equal faces): 4 external corners.
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L-shaped parapet plan: typically 2 external corners and 1 internal corner (use the internal corner product at re-entrant angles).
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Building with a projecting bay: additional external corners at each angle of the projection.
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Any 135-degree angle in the plan: use the 135-degree corner product, not this 90-degree version.
Installation
Fix the 4mm aluminium coping brackets along the run as normal. Position a bracket within 150-200mm of the corner piece on each leg of the corner. The corner piece itself does not typically carry a separate bracket beneath it; the bracket support comes from the positions closest to the corner on the adjacent straight sections.
Press the corner piece onto the brackets at the corner position and butt the straight sections up to it from each leg. Apply a continuous bead of colour coded sealant in the matching RAL to the internal face of each joint where the straight section meets the corner piece. The sealant bead at these joints is the primary weathertight seal. On an exposed parapet, both legs of the corner receive a sealant application.
Lock the adjacent coping sections to their brackets using colour coded fasteners in the matching RAL. Apply a neat finishing sealant bead on all external joint faces at the corner position, including both legs of the junction.
Where This Corner Piece Is Used
Rectangular Flat Roof Extensions
The most common application. A single-storey rear extension with a rectangular flat roof has four external parapet corners, each requiring one of these pieces. The corner provides a factory-formed, consistent profile at each building corner, matching the straight 3m coping lengths on each face.
Box Dormers
A box dormer typically has two 90° external corners where the front parapet meets the side returns. Each corner requires one of these pieces. The corner gives a clean finished junction at the most visible angles of the dormer installation, paired with closed stopends at the ends of the side returns.
Parapets with Multiple Building Projections
Commercial buildings with projecting elements, plant room enclosures and stepped plan forms generate multiple external corners across the parapet perimeter. Counting these accurately before ordering avoids shortage mid-installation on a made-to-order non-returnable product.
Boundary and Garden Walls
Low boundary walls and garden walls with aluminium sloping coping use the same corner piece at every right-angle junction. On a garden wall with a gate pier or a corner post, the 90° external corner gives a neat coping transition that the straight sections alone cannot provide.
Why Aluminium for Coping Corners
Coping corners are the most vulnerable position in any parapet run. They face the full weather exposure of two wall faces simultaneously, and a poorly formed or incorrectly sealed corner is the most common source of parapet water ingress on flat-roofed buildings. A factory-pressed aluminium corner profile, fabricated to the correct dimensions and fitted with a full sealant joint on each leg, removes the risk of a site-formed corner detail that relies on individual workmanship for its weathertightness.
The alternative to a purpose-made aluminium corner is a mitred joint between two straight sections. Mitred corners on aluminium coping are difficult to seal effectively and are a known long-term failure point. A factory-formed corner piece with the slope correctly resolved through the turn is the technically correct solution for every right-angle change of direction in a sloping coping run.
Why Choose Online Metal Store Ltd
Every component in the 2mm sloping coping 100mm system is manufactured at our Chelmsford facility. Corner pieces, lengths, stopends and brackets are all made to the same dimensional specification and finished in the same polyester powder coat process. When you order all system components together in the same RAL, they come from the same coating batch and arrive colour-matched. There is no tolerance variation between a corner ordered separately and a length ordered at a different time. Contact our team to discuss your system requirements, confirm your wall width dimensions, or get a quote for the full perimeter order including lengths, corners, stopends and brackets.
Complete Your 2mm Sloping Coping 100mm System
Every component you need for a complete installation:
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2mm Sloping Coping – 90° External Corner | 100mm External Leg (this product)
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2mm Sloping Coping – 90° Internal Corner | 100mm External Leg
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2mm Sloping Coping – 135° External Corner | 100mm External Leg
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2mm Sloping Coping – 135° Internal Corner | 100mm External Leg
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2mm Sloped Coping – Left Handed Closed Stopend | 100mm External Leg
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2mm Sloped Coping – Right Handed Closed Stopend | 100mm External Leg
For the full sloping coping system overview including 125mm external leg and 3mm commercial gauge versions, visit the Aluminium Sloping Coping collection page. To see how the system looks on a completed installation, view the aluminium sloped coping case study.
Frequently Asked Questions
What is the difference between an external and internal coping corner?
An external corner sits at an outside angle of the parapet, where the wall projects toward you as you look at the building. This is the most common corner type on rectangular buildings. An internal corner sits at a re-entrant angle, where the parapet forms an inside angle and the wall steps away from you. On a rectangular extension, all four corners are external. If your building has an L-shaped or complex plan, you may need both external and internal corners at different positions. The 90° internal corner is available in the same system.
What size corner do I order?
The same size as your straight coping lengths. If you have already worked out the coping size using wall width + 195mm, that is the size for both the lengths and the corner pieces. A 190mm wide parapet wall needs the 385mm size throughout the system, including at the corners.
How many corner pieces do I need?
One per external right-angle corner on the parapet plan. A standard rectangular flat roof extension has four external corners and needs four pieces. Count the corners on your drawing or measure on site before ordering. On non-rectangular plans, count carefully and distinguish between 90° and 135° angles to order the correct corner type at each position.
Does the corner use the same bracket as the straight lengths?
Yes. The 4mm aluminium coping bracket is the correct bracket for all components in the 2mm sloping coping 100mm system, including the corner pieces. Position brackets within 150-200mm of the corner piece on each leg of the adjacent straight sections. You do not normally need an additional bracket directly beneath the corner piece itself.
Can I use this corner with the 125mm external leg system?
No. This corner is fabricated for the 100mm external leg system. The 125mm system uses a different corner profile with wider legs. Using a 100mm corner on a 125mm installation produces a mismatch at the junction. For the 125mm external leg system, use the 90° external corner for the 125mm system.
Do I need to sealant both legs of the corner?
Yes. Apply a continuous bead of colour coded sealant in the matching RAL to the internal face of both joints where the straight sections butt up to the corner piece. Both legs of the corner are exposed to weather and both sealant joints are part of the weathertight line. Do not seal only one leg and leave the other to rely on the close fit of the profiles.
Ready to Order?
Select the size that matches your straight coping lengths from the dropdown above, choose your RAL colour, and add to basket. If you are ordering a full perimeter system and want to confirm your corner count, discuss the section mix, or get a quote for lengths, corners, stopends and brackets together, contact our team at sales@onlinemetalstore.co.uk or call +44 7907 239290, Monday to Saturday 6:30am to 4:30pm.
Custom Fabricated Item: Made to order. Please check your measurements before ordering. Non-returnable unless faulty. See our Refund and Returns Policy for full details.