Description
For shallow EWI builds and lighter retrofit specifications where insulation depth sits in the 70–90 mm range, the White Oversill 2.5 m × 140 mm delivers the right projection — sized to extend the original window sill outward across the new render face without the visual mass that deeper profiles introduce. Supplied through our window sill extensions and oversills collection, the profile is finished with industrial-grade powder coating and arrives wrapped in factory-applied PVC protective film. The white finish suits traditional and conservation-friendly facades where the anthracite-trim aesthetic of darker alternatives would clash with the existing building character. Stocked for trade self-collection from our Southampton counter.
What the 140 mm White Oversill Does in a UK Render or EWI System
The 140 mm White 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 projection is the most-specified depth across UK refurbishment work because it covers the most common build-up band — partial-fill retrofits, conservation-area specifications, and 80 mm graphite EPS systems where the Part L target lands without pushing into deeper builds.
The profile carries a factory-applied PVC protective film across the visible face, retained through the rendering stage and peeled away after surrounding work has cured to taping-clean. At 2.5 metres per unit, a single length serves window openings up to around 2.0 m wide once end-cap clearances are deducted — covering the majority of UK domestic windows without an intermediate joint that would otherwise create a visible line on the finished facade.
Why Trade Specifiers Choose the 140 mm White Oversill
- Most-specified depth across UK refurbishment: the 140 mm projection sits at the depth band that covers the largest share of UK EWI work — partial-fill retrofits, conservation-zone builds, and 80 mm graphite EPS specifications.
- 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: protects the visible face through transport and on-site handling, peeling away cleanly after surrounding render work is finished and eliminating the remedial cleaning unprotected aluminium requires.
- 2.5 m unit length: a single profile covers most UK domestic window widths without an intermediate joint, removing the visible line that two-piece installations introduce.
- White finish for traditional and conservation work: aligns with existing rainwater goods, fascia and trim detailing on heritage and conservation-area properties where dark-trim aesthetics would be inappropriate.
- Self-collection logistics: packed for damage-free transit from our Southampton warehouse, avoiding the courier-handling marks that visible facade products absorb on long transit.
Technical Specifications — 140 mm White Oversill Data Sheet
| Property | Value |
|---|---|
| Profile type | Window oversill extension for render and EWI systems |
| Material | Powder-coated aluminium extrusion, exterior grade |
| Colour | White |
| Length | 2.5 m |
| Projection (depth) | 140 mm |
| Insulation build accommodated | 70–90 mm sheltered, up to 100 mm on protected elevations |
| Finish | Industrial-grade powder coating |
| Surface protection | Factory-applied PVC film, removed post-install |
| Compatible end caps | White 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 White 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 around 48 mm of projection, comfortable drip clearance on sheltered elevations. On exposed weather-facing walls or builds approaching 100 mm insulation, step up to the 170 mm white oversill for the extra projection headroom.
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 behind the oversill 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 white end-cap pair at each reveal to close the watertight termination. For the full installation sequence — measurement, cutting, sealant sequencing 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, Cleaning Discipline
Retain the protective PVC film on the visible face throughout render application and surrounding finishing work. Although white shows render splatter less aggressively than anthracite, the film still saves the cleaning step that exposed surfaces require — peel only after all render work around the window has cured and any surface tidy-up is complete. Removing the film early — usually because the finish "looks fine" at basecoat stage — is the most common cause of remedial cleaning at handover, and the cleanup on cured cementitious splatter is harder than the prevention.
White powder-coated surfaces show cementitious render runoff more readily than darker finishes, so the surrounding cleaning discipline matters here too. A damp microfibre carried through the final basecoat and topcoat passes catches any wet splatter that reaches the oversill before cement sets onto the surface. 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 White Oversill
The 140 mm depth is the most-specified profile in the white range, and the discipline that separates a clean run from a marginal one sits in a handful of habits experienced UK installers repeat on every job.
- Confirm depth against the actual build, not the spec sheet: measured insulation thickness on site sometimes differs from drawing spec by 5–10 mm; do the build-up arithmetic on the wall before committing to the 140 mm depth over the 110 mm or 170 mm alternative.
- Set the fall before fixing, not after: a 5–10 degree outward fall is hard to correct once mechanical fixings are in; gauge the angle against a small spirit level held at the front edge before driving the first screw.
- Continuous sealant bead, not interrupted spots: a single uninterrupted neutral-cure silicone line along the back upstand is the watertight detail — interrupted spots become the first point of moisture ingress in driving rain.
- Leave 2–3 mm end clearance for caps: tight-cut profile ends prevent end caps seating cleanly and force the silicone bead to take up the gap as a visible joint line.
- Order end caps with the oversill, not after: caps ship separately and a 24-48 hour gap between deliveries breaks the install rhythm; one collection visit covers both items.
Is the 140 mm White Oversill Right for Your Project?
- Shallow EWI builds (70–90 mm insulation): the most-specified projection for partial-fill retrofits, conservation-zone work, and 80 mm graphite EPS specifications on sheltered elevations.
- Light retrofit (60 mm or below): step down to the 110 mm white oversill — 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 white oversill for graphite EPS at 90 mm, standard EPS at 100 mm, or any weather-facing facade where the 140 mm projection narrows the drip clearance margin.
- Contemporary anthracite trim schemes: the matched 140 mm anthracite oversill is the right specification for darker contemporary facade lines; white on anthracite trim runs creates an unintended high-contrast detail at the most visible point of the elevation.
FAQ — 140 mm White 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 170 mm white oversill?
Both profiles share the same 2.5 m length, powder-coated aluminium construction and white finish. The 140 mm is the most-specified depth for 70–90 mm insulation builds on sheltered elevations, while the 170 mm extends projection by 30 mm and becomes the right choice for 90–120 mm builds, exposed weather-facing walls, or any specification where the drip clearance margin needs to be more generous.
Are end caps included with the oversill?
No — end caps are sold separately as a matched pair. Order the white 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 sustain corner damage during courier transit at a rate that makes shipping uneconomic for a visible facade product. 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.
Should the protective PVC film come off before installation?
Keep the film in place throughout install and surrounding render work. Peel only after the render system around the window has fully cured and any surface cleaning is complete — the film exists specifically to protect the powder-coated face from render splatter and tooling marks during the build sequence, and removing it early is the most common cause of remedial cleanup at handover.
How does the white powder-coat finish hold up against ageing on UK facades?
Industrial powder coating delivers stable colour retention through prolonged UV exposure subject to manufacturer guidance, with white tones holding their density across typical UK exposure cycles. Performance is best maintained when the protective film is removed only after install and the surface is kept clean of cementitious residue from the surrounding render work — efflorescence-style staining on white profiles results from render runoff rather than coating failure.