Description
A rigid straight-profile corner bead cannot follow a curve — force it and the arris crimps, leaving a buckled line that no amount of render will hide. The PVC Arched Corner 2.5 m White solves that problem: a slender, flexible uPVC angle profile manufactured to conform to curved and arched geometry, for decorative plasterwork, rendered arches, and rounded reveals where a standard 90° rigid bead is the wrong tool. It is supplied as part of the render corner beads range at Renders World.
Where the White PVC Arched Corner Bead Performs Best on UK Curves
The PVC Arched Corner 2.5 m White is a flexible uPVC arch corner bead manufactured at reduced section weight (5.4 kg per 100 m) that conforms continuously to curves down to a 0.5 m minimum radius — designed for decorative internal arches, curved plaster features, rounded window and door reveals, and rendered external arches at 2–3 mm finished plaster or render depth. The narrow 3.3 mm arris and 23 mm wings keep the profile discreet once plastered over, producing a clean defined edge along the curve without a visible bead line proud of the finish.
This is not a rigid angle profile bent to shape on site — it is a flexible profile engineered for the radius. The lightweight section is what gives it the elastic range to follow a curve without crimping, and the result is a genuinely continuous arris where a scored-and-bent rigid bead would deliver a faceted polygonal approximation. It is the no-mesh white variant in the arched corner range, fixed mechanically into the plaster or thin render coat via non-corrosive pins or a mortar bed, without fibreglass wings to embed into a reinforced basecoat layer.
Why UK Installers Choose the Flexible Arched Profile
- Continuous flexibility to 0.5 m minimum radius: the profile follows curved geometry without crimping or buckling — a property of the lightweight engineered section, not something achievable by bending a rigid bead on site.
- Discreet 3.3 mm arris with 23 mm wings: sits inside a skim or thin render coat at 2–3 mm depth without standing proud, giving a defined edge line along the curve rather than a visible trim.
- Score-and-bend extension below 0.5 m: notching the wing backs at 20–30 mm intervals releases section tension and brings the effective working radius well below the unscored minimum for tight-radius arch heads.
- Compatible across plaster and render systems: works with gypsum-based skim and finish plasters, sand-and-cement, and acrylic top coats at 2–3 mm depth with no chemical reactivity at the bead-coat interface.
- Class 1Y fire classification: self-extinguishing on removal of flame source under BS 476 testing for this profile class, subject to confirmation against the wider system fire strategy.
- Alkali-resistant, UV-stable uPVC: survives long-term contact with cementitious and gypsum coats and exterior UV exposure without embrittlement, yellowing, or dimensional change.
- Light, fast-cutting section: at 5.4 kg per 100 m the profile handles quickly on site and cuts cleanly with tin snips or a fine-tooth saw without deforming the slender arris geometry.
Technical Specifications — White Arched Corner Bead Data
| Property | Value |
|---|---|
| Length | 2,500 mm |
| Arris width | 3.3 mm |
| Wing width | 23 mm (per wing) |
| Suitable plaster/render depth | 2–3 mm |
| Minimum bend radius | 0.5 m (continuous curve without notching) |
| Material | Exterior-grade flexible uPVC · alkali-resistant · lead-free · UV-stabilised |
| Mesh | None — mechanical fixing via pins or mortar bed |
| Weight | 5.4 kg per 100 m |
| Colour | White |
| Fire classification | Class 1Y — self-extinguishing on removal of flame (BS 476, subject to system confirmation) |
| Standard reference | BS EN 13914-1&2:2016 (subject to system confirmation) |
| Application temperature | +5 °C to +30 °C (air and substrate) |
| Storage | Vertical or horizontal (supported along length), out of direct sunlight |
| Pack size | Single 2.5 m length (trade packs also available) |
Specification data is drawn from CB2A-class technical references for flexible uPVC arch corner bead profiles. Confirm against the current manufacturer's datasheet for warranty-critical or specification-governed applications.
How to Apply the Arched Corner — Bending, Scoring, and Fixing to a Curve
On a concave curve (the inside of an arch), bend the profile gently and continuously to the radius before fixing — the flexible uPVC will hold a smooth arc without springing back significantly once pinned. Fix with non-corrosive lost-head nails or stainless pins through the wings at 200–300 mm centres, working from the centre of the curve outward to avoid introducing a kink at the fixing points. Apply plaster or render over the wings immediately after fixing so the profile is encapsulated before it has time to recover toward straight.
For radii approaching or below the 0.5 m minimum, score the back of the wings at 20–30 mm intervals with a fine saw or sharp knife — this releases section tension along the wing and lets the arris follow a tighter curve without the nose crimping. On a convex curve (the outside of a rounded column or pilaster), the same scoring technique on the outer wing face allows the profile to open slightly wider than its manufactured angle. Trim ends with tin snips or a fine-tooth saw; the light section cuts cleanly without deforming the arris. For the full corner-bead installation sequence including reveal, head, and base terminations across profile types, see the corner bead installation step-by-step guide.
Installation Notes — Coat Encapsulation and Mesh-Integrated Alternatives
Work within the +5 °C to +30 °C window for both air and substrate, and aim to fix and over-coat in the same session so the bead and surrounding plaster or render move together through the initial cure. On gypsum-based skim systems indoors, prime high-suction substrates lightly before plastering the arch so the skim does not flash off at the bead before it can be ruled flat across the arris.
For external rendered arches on EWI build-ups where the corner reinforcement needs to integrate with a fibreglass mesh basecoat layer, this no-mesh profile is not the right specification — the PVC arched corner bead with mesh carries fibreglass wings that embed into the basecoat alongside the field reinforcement and tie the curved corner into the composite system. For straight 90° external corners on the same EWI elevation, the corner PVC render bead with mesh is the matching rigid mesh-wing profile. Wider profile-selection guidance covering reveals, arches, lintels, and sills together is set out in the render detailing around windows and doors guide.
Pro Tips From UK Installers Working Arched and Radius Corners
The most common error on curved corner work is reaching for a rigid bead first. Scoring deeply through one wing of a heavy rigid profile, bending it to the arch, and rendering over the result delivers a polygonal approximation of a curve — and every score point becomes a stress concentration that opens up as a hairline crack at the first thermal cycle. The flexible arch profile exists because elastic-range bending of a thin engineered section produces a genuinely continuous curve, and a rigid bead forced to the same shape cannot.
- Bend before fixing, not after: set the curve into the profile by hand before the first pin goes in — pinning a straight bead and trying to push it to the arch as you nail leaves stress concentrations at every fixing point.
- Work from the apex outward: on an arched opening, start fixing at the crown of the arch and progress symmetrically down each side, so any final length adjustment falls at the springing line where it is easiest to dress with plaster.
- Score evenly for tight radii: when the curve requires notching the wings, keep the score depth and spacing identical along the length — uneven scoring telegraphs through the finished arris as a wavy line under raking light.
- Calculate developed length first: arc length = radius × angle in radians; add 10–15% for cuts and joint allowances. A 1 m radius semi-circular arch develops to roughly 3.14 m, so one 2.5 m length will not span it without a joint.
- Store flat or fully supported: the same flexibility that makes the profile useful on a curve means it takes a permanent set if stored unsupported over an edge — keep lengths flat or vertical between deliveries.
Is the White Arched Corner Bead Right for Your Project?
- Decorative internal arches, curved plaster features, and rounded reveals at 2–3 mm finished plaster or render depth: the primary use case — the flexible section and narrow 3.3 mm arris produce a smooth, continuous edge that rigid profiles cannot replicate.
- Rendered external arches on EWI build-ups with a reinforced basecoat: specify the PVC arched corner bead with mesh instead — its fibreglass wings integrate the curved corner into the field reinforcement layer.
- Straight 90° external corners on thin-coat render systems: this flexible arch profile is not suited to straight corners — the corner PVC render bead with mesh is the correct rigid mesh-wing profile for those locations.
- Straight traditional render corners at 6–12 mm depth: use the rigid 6 mm or 10 mm PVC corner bead no mesh sized to the finished render depth on straight walls.
- Ordering for a full arched feature: calculate the developed length of the curve, add 10–15% for cuts, and order in 2.5 m lengths — the light weight makes over-ordering low-risk and storage flat or vertical preserves the profile geometry between site visits.
Stocked for next-working-day despatch in trade quantities. Confirm the curve radius against the 0.5 m unscored minimum before ordering — tighter radii are achievable with the wing-scoring technique, but specifying the geometry up front keeps the take-off accurate.
FAQ — Arched Corner Bead Radius, Compatibility, Ordering
What is the tightest curve this bead can follow?
The profile conforms continuously to a minimum radius of 0.5 m without notching. For tighter radii, score the back of the wings at 20–30 mm intervals with a fine saw or sharp knife to release section tension — this brings the effective working radius considerably below 0.5 m while keeping the arris line smooth between the score points. The scoring interval determines how tight a curve is achievable: closer scores allow tighter bends.
How does this differ from the arched corner bead with mesh?
This no-mesh white arch profile is fixed mechanically with non-corrosive pins into plaster or a thin render coat at 2–3 mm depth — the correct choice for decorative plastering arches, internal curved features, and rendered arches where no fibreglass reinforcement layer is present. The arched corner bead with mesh carries fibreglass wings designed to embed into a reinforced basecoat on EWI build-ups, tying the curved corner into the composite reinforcement system. The two profiles address different systems and different finishing depths.
How do I calculate how many beads I need for an arch?
Calculate the developed length of the curve using arc length = radius × angle in radians, then add 10–15% for cuts and joint allowances. A 1 m radius semi-circular arch develops to approximately 3.14 m, requiring two 2.5 m lengths with a butt joint at the crown or the springing line. For full-circle features such as round windows, multiply the diameter by π and add the same allowance.
Can this bead be used externally on rendered arches?
The exterior-grade uPVC formulation is suitable for external use in contact with sand-and-cement and acrylic render systems at 2–3 mm coat depth. For external arches on EWI build-ups where a reinforced basecoat is specified, the mesh-wing arched corner bead is the more appropriate choice because it integrates the corner reinforcement into the field mesh layer. For external arches on direct-to-substrate renders, this no-mesh profile is a practical option subject to mechanical fixing at the appropriate centres.
Is this profile suitable for standard skim coat thicknesses?
At 2–3 mm suited plaster and render depth, the profile is compatible with finish skim coats applied directly over plasterboard or a scratch coat. The 3.3 mm arris finishes at or just below the skim surface, producing a defined shadow line along the curve. For thicker render coats from 6 mm upward, the arris will be buried, which is acceptable on internal feature work, though the deeper rigid profile variants in the range are better matched to those build-up depths on straight corners.
How do I cut the bead to length on site?
Cut with tin snips or a fine-tooth saw — the lightweight 5.4 kg per 100 m section cuts cleanly without deforming the arris. Deburr the cut end lightly before fitting if a clean butt joint is needed at a termination. At joints on long curves, butt cut ends tightly and ensure the plaster or render coat bridges the joint continuously so the finished line reads as a single uninterrupted curve.