Description
First-time EWI on a pre-1970s solid-wall home means the original sill suddenly sits behind the new render face, and the White Oversill 2.5 m × 110 mm restores that lost drip edge on light-touch builds up to around 60 mm insulation. It is the shallowest depth in the white range, matched to the white fascia and rainwater goods of traditional UK housing, film-protected, and stocked for trade self-collection from our Southampton counter.
What the 110 mm White Oversill Does in a UK Render or EWI System
When a solid wall gains its first 40–60 mm of external insulation, the original window sill no longer projects past the render face, and the 110 mm White Oversill restores that overhang by carrying the sill outward over the new build to shed rainwater clear of the wall. It is the shallowest projection in the white range, sized for insulation up to around 60 mm, which covers the budget-constrained and planning-limited refurbishment that represents the largest share of first-time UK domestic EWI. The profile sits within the wider window sill extensions and oversills range for coordinated white detailing.
White remains the default across this market because pre-1970s terraces, semis and detached homes carry white timber or uPVC fascia, white rainwater goods and white-painted detailing, so a white oversill reads as part of the existing scheme rather than a contrasting band. At 2.5 metres per unit, a single profile typically serves openings up to 2.0 m wide once end-cap allowances are deducted, giving the unbroken trim line residential refurbishment depends on.
Why Trade Specifiers Choose the 110 mm White Oversill
- Sized for first-time EWI builds: the 110 mm depth accommodates insulation up to around 60 mm, the band typical of light-touch refurbishment and budget-constrained EWI on traditional UK housing.
- Industrial powder-coat white finish: the factory-applied coating delivers consistent colour density across the trim, outperforming painted alternatives that show edge wear and colour drift over service life.
- PVC protective film during install: the factory-applied film safeguards the visible face through transport and handling, peeling cleanly after surrounding render work has cured.
- 2.5 m unit length: a single profile covers most domestic window widths without an intermediate joint, delivering the unbroken trim line residential refurbishment depends on.
- Coordinated with traditional trim systems: aligns with white fascia, white uPVC rainwater goods and white-painted timber detailing typical of UK pre-1970s housing.
Technical Specifications — 110 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) | 110 mm |
| Insulation build accommodated | Up to 60 mm plus basecoat and topcoat |
| Recommended drip-edge projection | 30–40 mm beyond finished render face |
| Fixing centres | 300 mm along rear upstand |
| 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 |
How to Fit the 110 mm White Oversill — Build-Up Match, Fall, Sealing
To confirm the 110 mm depth is right, add the insulation thickness to a basecoat-and-topcoat allowance of typically 10–15 mm combined, then add a 30–40 mm minimum drip projection beyond the finished render face. A 50 mm EPS build with 12 mm of render totals 62 mm, so the 110 mm oversill leaves about 48 mm of projection — comfortable drip clearance for light-touch retrofit. For builds pushing into the 70–90 mm band, step up to the 140 mm white oversill, since the 110 mm projection would then underdeliver on overhang past the render face.
Fit the oversill after the basecoat and reinforcing mesh have cured but before the decorative finish coat. 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 white 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 sequence of measurement, cutting, sealant routing and basecoat integration, the window sill extensions installation guide walks through the trade method with worked examples.
Installation Notes — Fall Angle, Film Retention, White-Finish Discipline
Retain the protective PVC film on the visible face through render application and surrounding finishing. White surfaces show cementitious render runoff and basecoat residue more visibly than darker trim, and once cement starts to set on the powder coat it can leave a permanent shadow on the white face. The film prevents that contact during the build, so peel it only after all render work has cured to taping-clean and any surface cleaning around the window is complete.
On shallow projections the fall angle carries less margin for error than on deeper profiles, because a smaller drip clearance leaves less room for water that tracks back rather than draining forward. Verify the 5–10 degree outward fall against a spirit level held at the front edge before the mechanical fixings drive home, not after, since corrections at the fixing stage distort the powder-coat 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 guide covers the full junction-by-junction coordination of profiles around openings.
How the 110 mm Depth Compares to Deeper White Oversills
The white oversill family runs across four projections on the same 2.5 m profile and finish, so choosing between them comes down to insulation build and exposure. The 110 mm is the shallowest, the workhorse of light-touch first-time retrofit, with the deeper depths above it covering standard and deep builds.
| Variant | Key Spec | When to Choose |
|---|---|---|
| 110 mm white oversill | 110 mm projection | First-time light EWI, up to 60 mm |
| 140 mm white oversill | 140 mm projection | Shallow EWI, 70–90 mm insulation |
| 170 mm white oversill | 170 mm projection | Standard workhorse EWI, 90–120 mm |
Pro Tips From UK Installers Using the 110 mm White Oversill
The 110 mm white is the light-touch workhorse, distinct from the deeper 170 mm that dominates standard EWI, and the discipline that keeps a first-time-retrofit run clean sits in matching depth to the actual build and protecting the white finish through the programme.
- Match depth to the ECO-funded scope, not the deepest option: first-time budget retrofits max out around 40–60 mm insulation, so the 110 mm is genuinely correct here rather than a compromise, and over-specifying a deeper profile creates a visible step at the window.
- Wipe render splatter off white immediately: a damp microfibre carried through the final basecoat and topcoat passes catches wet splatter before cement sets and shadows the white powder coat permanently.
- Bed with white silicone, never grey: a colour-matched white neutral-cure bead disappears at the back upstand, while grey sealant reads as a contrasting joint line under raking light on white trim.
- Verify fall before fixing on the shallow profile: the smaller drip clearance at 110 mm leaves less tolerance for a flat or reversed fall, so gauge the 5–10 degree angle before the first screw drives home.
- Order caps and silicone in one visit: the white end-cap pair ships separately, so a single self-collection trip for profile, caps and white silicone keeps a single-elevation refurbishment on programme.
Is the 110 mm White Oversill Right for Your Project?
- Light-touch first-time EWI (up to 60 mm insulation): the most-specified projection for traditional UK housing receiving its initial external insulation under budget-driven or planning-constrained refurbishment scopes.
- Light-to-medium retrofit (70–90 mm insulation): step up to the 140 mm white oversill, since the 110 mm projection would underdeliver on overhang past the finished render face.
- Standard EWI (90 mm and above): use the workhorse 170 mm white oversill for graphite EPS at 90 mm or standard EPS at 100 mm.
- Traditional and heritage facades: the white finish coordinates with white fascia, rainwater goods and trim systems typical of UK pre-1970s residential housing where dark-trim alternatives would clash.
- Contemporary dark-trim schemes: the matched 110 mm anthracite oversill covers the same light-build band in RAL 7016 where the facade calls for dark trim.
FAQ — 110 mm White Oversill Coverage, Compatibility, Ordering
Is 60 mm of insulation enough for meaningful U-value improvement?
On a solid uninsulated wall the reduction from around 60 mm of EPS or mineral wool is substantial, typically improving the wall from roughly 1.7 W/m²K toward the 0.4–0.5 W/m²K range depending on the existing construction and insulation lambda, subject to project-specific calculation. For Part L compliance on extensions or major refurbishment, deeper builds may be required; for general thermal upgrade on existing housing, a light build delivers genuine gains while keeping the scope manageable.
How do I confirm the 110 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 60–70 mm, the 110 mm depth gives the right overhang; above that, the 140 mm depth is the safer specification.
How does the 110 mm compare to the 140 mm and 170 mm white oversills?
All three share the same 2.5 m length, powder-coated aluminium construction and white finish. The 110 mm covers first-time light builds up to around 60 mm insulation, the 140 mm covers shallow EWI around 70–90 mm, and the 170 mm is the workhorse for standard EWI around 90–120 mm. Selecting the depth that matches the actual build avoids both inadequate drip clearance and the visible step overspecified profiles create at the window detail.
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 visible facade trim. Self-collection from our Southampton counter ensures the profile arrives with the powder-coat edge intact and ready for install, and trade buyers collecting larger orders regularly can arrange scheduled pickup in advance.
Will the white finish stain from cementitious render runoff?
White trim shows render runoff and efflorescence-style staining more visibly than darker alternatives. The PVC protective film prevents direct contact during the install, so keep the film in place until all render work has cured, and any post-install runoff cleans off with mild detergent before it sets. Proper bedding and drainage detailing during install minimises the chance runoff reaches the trim face in service.