Description
Restored drip-edge drainage at window openings on shallow contemporary EWI builds starts with the Anthracite Oversill 2.5 m × 140 mm — a 2.5-metre powder-coated aluminium profile sized for 70–90 mm insulation builds where the dark-trim aesthetic of modern UK facades meets partial-fill retrofit and conservation-zone constraints. Supplied through our window sill extensions and oversills collection, the profile is finished with industrial-grade powder coating in the RAL 7016 family and arrives wrapped in factory-applied PVC protective film. Stocked for trade self-collection from our Southampton counter.
What the 140 mm Anthracite Oversill Does in a UK Render or EWI System
The 140 mm Anthracite Oversill is a 2.5-metre powder-coated aluminium profile that fits over the existing window sill, extending the drip edge across an EWI build of 70–90 mm insulation plus basecoat and topcoat, restoring the rainwater shedding that the original sill — sized for an uninsulated wall — can no longer deliver. The 140 mm depth covers the shallow-build band on contemporary anthracite specifications: partial-fill retrofits on modern buildings, conservation-zone work where local planning constrains insulation depth, and 80 mm graphite EPS systems where Part L targets are hit without pushing into deeper builds. For standard 90–120 mm EWI on contemporary facades, step up to the 170 mm anthracite oversill — the workhorse depth in the range.
The anthracite finish corresponds to the RAL 7016 family that defines current UK contemporary specification on residential and commercial facades alike, pairing the oversill line with anthracite window frames and rainwater goods on a continuous facade tone. The factory-applied PVC protective film stays in place through the rendering stage and peels away after surrounding work has cured to taping-clean, with a single 2.5 m length typically serving window openings up to around 2.0 m wide once end-cap clearances are deducted.
Why Trade Specifiers Choose the 140 mm Anthracite Oversill
- Sized for shallow contemporary EWI builds: the 140 mm depth covers 70–90 mm insulation on partial-fill retrofits, conservation-zone work, and 80 mm graphite EPS specifications where the dark-trim aesthetic of modern UK facades meets shallow-build constraints.
- Visual proportion on minimal-detail elevations: on contemporary architecture where window detailing is intentionally restrained, the 140 mm projection reads as a quiet horizontal line rather than the heavier shadow a deeper profile casts.
- Industrial powder-coat finish: the factory-applied coating delivers consistent colour density and bonded surface protection across a service life that matches the typical 25–30 year EWI design horizon.
- Factory-applied PVC film: safeguards the visible face through transport and on-site handling, eliminating the additional cleaning step that exposed dark surfaces would otherwise require after render work.
- 2.5 m unit length: a single profile covers most UK domestic window widths in one piece, removing the visible joint line that two-piece installations introduce on a dark trim where any joint reads more visibly.
- Self-collection logistics: packed for damage-free transit from our Southampton warehouse, avoiding the courier-handling marks that anthracite shows more readily than white finishes.
Technical Specifications — 140 mm Anthracite Oversill Data Sheet
| Property | Value |
|---|---|
| Profile type | Window oversill extension for render and EWI systems |
| Material | Powder-coated aluminium extrusion, exterior grade |
| Colour | Anthracite (RAL 7016 family) |
| Length | 2.5 m |
| Projection (depth) | 140 mm |
| Insulation build accommodated | 70–90 mm sheltered, up to 100 mm on protected elevations |
| Recommended drip-edge projection | 30–40 mm beyond finished render face |
| Fixing centres | 300 mm (countersunk screws along back upstand) |
| Finish | Industrial-grade powder coating |
| Surface protection | Factory-applied PVC film, removed post-install |
| Compatible end caps | Anthracite end-cap pair (sold separately) |
| Delivery | Self-collection from Southampton — courier transit excluded |
| Storage | Flat, dry, protective film retained until install |
How to Fit the 140 mm Anthracite Oversill — Build-Up Match, Fall, Sealing
To confirm the 140 mm depth is the right specification, add the insulation thickness to the basecoat and topcoat allowance (typically 10–15 mm combined) and then add a 30–40 mm minimum drip projection beyond the finished render face. An 80 mm graphite EPS build with 12 mm of basecoat and topcoat totals 92 mm — the 140 mm oversill leaves about 48 mm of projection, comfortable drip clearance on sheltered contemporary elevations. For shallower 50–70 mm insulation builds typical of light retrofit, step down to the 110 mm anthracite oversill; for standard 90–120 mm builds on exposed walls, step up to the 170 mm anthracite oversill for the safer projection margin.
Fit the oversill after the basecoat and reinforcing mesh have cured but before the decorative finish coat is applied. Set the profile with a slight outward fall — typically 5–10 degrees — so rainwater drains clear of the wall rather than tracking back toward the substrate. Bed the back upstand into a continuous neutral-cure silicone seal against the original masonry sill, fix mechanically at 300 mm centres along the back upstand, and pair with the matching anthracite end-cap pair at each reveal to close the watertight termination. For the full installation sequence — measurement, cutting, sealant routing and basecoat integration — the window sill extensions installation guide for UK projects walks through the trade method with worked examples.
Installation Notes — Fall Angle, Film Protection, Dark-Finish Discipline
Retain the protective PVC film on the visible face throughout render application and surrounding finishing work. Anthracite shows render splatter and basecoat marks far more visibly than white profiles, and the film prevents the additional cleaning step that exposed dark surfaces would otherwise require. Peel only after all render work around the window has cured to taping-clean and any final tidy-up is complete; premature removal at basecoat stage exposes the dark powder-coat to drips and trowel contact that mark the finish permanently.
On contemporary architecture the 140 mm depth is often specified precisely because of its quieter horizontal line — that visual intent depends on consistent installation height across every opening on the elevation. Set a string-line or laser level between the first and last openings before fixing the intermediate profiles, so the finished oversill line reads as one continuous datum across the facade rather than a series of small height variations. Oversill detailing sits within the broader window reveal treatment that also includes stop beads at jambs and corner beads at external arris points; the render detailing around windows and doors pillar guide covers the full junction-by-junction coordination of profiles around openings.
Pro Tips From UK Installers Using the 140 mm Anthracite Oversill
The 140 mm anthracite is the depth that gets specified on contemporary architecture where window detailing is intentionally restrained, and the discipline that separates a clean install from a marginal one sits in handling the dark finish well and protecting the line that defines the elevation.
- Set a horizontal datum across the elevation: a string-line or laser between the first and last opening on each facade before fixing the intermediate oversills locks the finished line as one continuous datum — the visual brief that drives anthracite specification depends on it.
- Order the cap pair with the oversill, not after: the 140 mm anthracite is the most-stocked dark oversill SKU and ships fast from our Southampton warehouse, but the end-cap pair is a separate line item; one combined collection visit keeps the install sequence intact.
- Protect the powder-coat edge in transit and on site: anthracite shows transit marks more readily than white; carry the profile on edge rather than flat-stacked on the van floor, and rest cut lengths on a foam offcut rather than against a hard surface before fitting.
- Verify build-up against actual on-site measurement: drawing specifications sometimes call 80 mm but the as-installed insulation depth varies by 5–10 mm; confirm the build-up with a tape against the cured basecoat before committing to the 140 mm depth over the 170 mm alternative.
- Fit before scaffold strike, not after: ladder-fitting anthracite oversills after scaffold removal sacrifices the bedding precision the finish demands; close every opening during the final scaffold-up day with profiles cut, bedded, fixed and capped.
Is the 140 mm Anthracite Oversill Right for Your Project?
- Shallow contemporary EWI builds (70–90 mm insulation): the right projection for partial-fill retrofits, conservation-zone work on contemporary buildings, and 80 mm graphite EPS specifications where the dark-trim aesthetic of modern facades meets shallow-build constraints.
- Light retrofit (50–70 mm insulation): the 110 mm anthracite oversill is the right match — the 140 mm depth would project further than the build requires and introduce a visible step beyond the finished render face.
- Standard EWI (90–120 mm insulation, exposed elevations): step up to the 170 mm anthracite oversill — the workhorse depth for graphite EPS at 90 mm, standard EPS at 100 mm, and any weather-facing facade where the 140 mm projection would narrow the drip clearance margin.
- Traditional and conservation facades: the 140 mm white oversill is the matched specification for properties where existing fascia, rainwater goods and architectural character call for a continuous white trim line rather than the dark contemporary alternative.
FAQ — 140 mm Anthracite Oversill Coverage, Compatibility, Ordering
How do I confirm the 140 mm depth is right for my project?
Measure the total finished build from the original masonry face outward — insulation thickness plus adhesive layer plus basecoat plus decorative finish. The oversill projection should exceed that measurement by 30–40 mm to deliver proper drip clearance past the finished render face. For builds totalling around 90–100 mm, the 140 mm depth gives the right overhang on sheltered elevations; on exposed walls or above 100 mm total build, the 170 mm depth is the safer specification.
How does the 140 mm compare to the 110 mm and 170 mm anthracite oversills?
All three share the same 2.5 m length, powder-coated aluminium construction and RAL 7016 anthracite finish. The 110 mm covers light retrofit (50–70 mm insulation), the 140 mm covers shallow contemporary EWI (70–90 mm insulation), and the 170 mm is the workhorse for standard EWI (90–120 mm insulation). Selecting the depth that matches the actual build avoids both inadequate drip clearance and the visible step that overspecified profiles create on contemporary minimal-detail elevations.
Are end caps included with the oversill?
No — end caps are sold separately as a matched anthracite pair. Order the anthracite end-cap pair alongside the oversill so both arrive ready for the install sequence in one self-collection visit. One pair closes both ends of one oversill run.
Why is delivery limited to self-collection?
Powder-coated extrusions of this length and finish sustain corner damage during courier transit at a rate that makes shipping uneconomic for a visible facade product, and anthracite shows transit marks more readily than white. Self-collection from our Southampton counter ensures the profile arrives with the powder-coat edge intact and ready for install. Trade buyers collecting larger orders regularly can arrange scheduled pickup in advance to suit project schedules.
Can the anthracite finish be painted to a different colour?
The powder-coated aluminium surface will accept an over-paint with a suitable metal primer and exterior topcoat, though the factory RAL 7016 finish typically outperforms site-applied paint on adhesion, UV stability and scratch resistance. For most UK contemporary EWI projects, the factory anthracite matches the prevailing dark window frame and fascia specification without requiring custom colouring at order or rework on site.
How does the anthracite finish age on UK coastal and exposed facades?
Powder-coated aluminium is the standard specification for UK coastal and exposed-elevation work because it does not corrode like steel and resists the UV and salt-spray loading that degrades softer finishes. The factory coating provides the long-term colour and surface stability these conditions demand, and the protective PVC film during installation prevents the early-life surface marking that otherwise compromises long-term appearance on dark trim.