Description
At 220 mm projection sized for 140–200 mm insulation builds, the White Oversill 2.5 m is the deepest profile in the range, carrying the original sill outward across the solid-wall deep-retrofit builds where thick insulation has pushed the finished facade well past the original sill line. Powder-coated brilliant white to match the uPVC frames across most UK housing stock, film-protected, and stocked for trade self-collection from our Southampton warehouse.
What the 220 mm White Oversill Does on Deep EWI Builds
At 220 mm projection over a 2.5 m brilliant-white powder-coated profile, the White Oversill carries the original window sill outward across EWI insulation builds of 140–200 mm, delivering the 30–40 mm drip projection past the finished render face that good EWI detailing practice expects. It handles the broad mid-to-deep band of UK insulation work, from 140 mm graphite EPS through 170 mm mineral wool and on to dual-layer 200 mm builds on demanding solid-wall retrofits. The profile sits within the wider window sill extensions and oversills range for coordinated white detailing across the elevation.
White is the volume specification across UK EWI because most uPVC window frames installed since the 1990s are white, and a matched sill line reads as a single architectural element rather than a contrasting band. On local-authority and housing-association programmes that account for much of the deep-retrofit pipeline, white trim is the default, and at 220 mm depth the profile addresses the deepest insulation builds those programmes specify when targeting demanding whole-wall U-values, subject to project-specific fabric calculation.
Why UK Installers Specify White for Mainstream Deep-Build Projects
- Matches the dominant uPVC frame colour: the brilliant white powder coat aligns with the standard frame specification on the majority of UK housing stock, holding a single colour line across the window detail without on-site touching-in.
- Sized for the volume deep-build band: the 220 mm projection covers 140–200 mm insulation in a single SKU, absorbing a broad range of project depths where white is the volume colour choice.
- Specified across local-authority and HA programmes: the colour and depth combination is the workhorse choice on social-housing retrofit where solid 225 mm brick receives 150–170 mm of mineral wool toward Part L targets, subject to project compliance calculation.
- UV-stable powder coat: the brilliant white finish resists yellowing over the 25–30 year service life of a certified EWI system, holding colour parity with frames and neighbouring elevations across a phased programme.
- Factory PVC film through long programmes: deep-build EWI runs longer than shallower work, and the film protects the white face through extended scaffold time, splatter and multi-trade interfaces around the window.
- Part of a four-depth family: the 220 mm sits at the top of a graded range, with the 110 mm, 140 mm and 170 mm white oversills below it, so a mixed-depth elevation details in one colour family across every opening.
Technical Specifications — 220 mm White Oversill Data Sheet
| Property | Value |
|---|---|
| Profile type | Window oversill extension — deepest projection |
| Material | Powder-coated aluminium extrusion, exterior grade |
| Colour | Brilliant white |
| Length | 2.5 m (single unit) |
| Projection (depth) | 220 mm |
| Insulation build accommodated | 140–200 mm (with basecoat and topcoat) |
| Drip-edge projection past render | 30–40 mm typical at correct build depth |
| Recommended fixing centres | 300 mm along rear upstand |
| Surface protection | Factory-applied PVC film, removed at handover |
| Compatible end caps | White end-cap pair (sold separately) |
| Delivery route | Self-collection only — Southampton warehouse |
| Storage | Flat, dry, protective film retained until install |
How the 220 mm White Oversill Fits Into the EWI Sequence
The oversill goes on after the insulation boards are bonded and mechanically fixed but before the basecoat and mesh reinforcement layer, so the basecoat can be worked tight against the trim edge afterwards and lock the profile into the finished build. Bed the rear upstand into a continuous low-modulus silicone or hybrid sealant bead against the original masonry sill, then fix mechanically at 300 mm centres along the upstand with countersunk screws. Set the trim with a slight outward fall, typically 5–10 degrees, so rainwater drains clear of the wall rather than tracking back behind the profile onto the insulation.
At 220 mm projection the structural loading is meaningfully greater than at shallower depths, so verify wind-uplift capacity against the project exposure category, particularly on south-westerly elevations facing prevailing UK weather. Pair the profile with the matching white end-cap pair at each reveal to close the watertight termination. For the full installation sequence covering measuring, cutting, sealing and end-cap integration as a complete system, the window sill extensions installation guide walks through the worked process across the whole trim family.
Installation Notes — Cutting, Sealing, Film Removal
For the best result, measure every opening individually. On solid-wall retrofits where the 220 mm depth is most often specified, original reveals vary by 15–20 mm between openings on the same elevation because of historical settlement and brick irregularity. Cut each profile to width with a fine-toothed metal-cutting blade, leaving 2–3 mm clearance at each end for the end cap to seat without forcing, then deburr the cut edge with fine-grit abrasive so the end-cap seal sits cleanly.
Use a low-modulus silicone or hybrid sealant along the rear upstand, since high-modulus products can crack as the aluminium cycles with temperature, and any break in the sealant line behind a 220 mm profile lets water track directly onto the insulation. Leave the PVC protective film intact through the basecoat, mesh and topcoat applications, peeling it only once the topcoat has fully cured and scaffolding is being struck, so the white face arrives at handover without remedial cleaning marks. 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 220 mm Depth Compares to Shallower White Oversills
The white oversill family runs across four projections to cover the full UK insulation depth band in a single colour. Selecting the right depth is a measurement exercise: total finished build from the original masonry face outward — insulation plus adhesive, basecoat and topcoat — should sit roughly 30–40 mm short of the oversill projection so the drip edge clears the render face properly.
| Variant | Key Spec | When to Choose |
|---|---|---|
| 140 mm white oversill | 140 mm projection | Shallow EWI, 70–90 mm insulation |
| 170 mm white oversill | 170 mm projection | Workhorse solid-wall retrofit, 90–140 mm |
| 220 mm white oversill | 220 mm projection | Deep solid-wall retrofit, LA/HA, 140–200 mm |
For builds below 140 mm finished insulation, the 170 mm white oversill is the correct workhorse depth and avoids the unnecessary architectural step an over-specified 220 mm projection would create. Where the project specifies dark trim to match anthracite frames or a contemporary contrast facade, the 220 mm anthracite oversill covers the same projection in RAL 7016 powder coat.
Pro Tips From UK Renderers Fitting the 220 mm White Oversill
The 220 mm white is the deepest and most-handled profile on social-housing deep-retrofit programmes, and the discipline that keeps a multi-window run clean sits in a handful of habits experienced UK renderers repeat on every deep-build job.
- Check van load space before collecting: at 2.5 m length this is the largest oversill in the range, and multi-window jobs easily reach a dozen profiles plus end-cap packs, so confirm load capacity before the trip rather than at the counter.
- Count end-cap pairs against openings, not metres: the white end-cap pair is sold separately and one pair closes one oversill run, so order pairs against window count rather than linear metres of profile.
- Leave 2–3 mm clearance on every cut: the deeper the profile, the more a tight-cut length visibly bows if forced into a reveal 1–2 mm narrow, so the end clearance is the rule that protects the visible trim line at 220 mm.
- Do the overhang arithmetic before ordering: add insulation thickness plus 12–15 mm of basecoat and topcoat to reach finished build, then confirm the 220 mm projection clears that figure by 30–40 mm — if it doesn't, the wrong depth has been specified.
- Keep the film on through the whole programme: on long deep-build jobs the film's UV resistance keeps the powder coat unmarked through extended scaffold periods, and pulling it early is the single most common cause of remedial cleaning at handover.
Is the 220 mm White Oversill Right for Your Project?
- Deep solid-wall retrofit EWI: the correct projection for 140–200 mm insulation builds typical of Victorian, Edwardian and inter-war masonry receiving thick graphite EPS or mineral wool toward whole-wall U-value targets, subject to project fabric calculation.
- Local-authority and housing-association programmes: the workhorse depth and colour combination on social-housing retrofit, where matched white trim aligns with the standard uPVC frame specification across blocks of dwellings.
- High-performance new build: a sound choice on developer programmes forward-specifying insulation depth to 150–180 mm, where the trim depth needs to track the build, subject to the project's own performance specification.
- Standard EWI at 90–140 mm insulation: the 170 mm white oversill is the workhorse depth, since the 220 mm projection would sit past the render face and add unnecessary architectural mass.
- Anthracite or contrast-trim facades: the 220 mm anthracite oversill covers the same insulation band in RAL 7016, matching dark frames and contemporary facade specifications.
FAQ — 220 mm White Oversill Coverage, Compatibility, Ordering
What insulation thickness suits the 220 mm white oversill?
The 220 mm depth accommodates insulation build-ups of 140–200 mm plus the basecoat and topcoat layer, typically 10–15 mm combined. For a 170 mm mineral wool slab with 12 mm of basecoat and topcoat, total added wall thickness is approximately 182 mm, so the 220 mm profile provides around 38 mm of drip-edge projection — within the 30–40 mm range expected by good EWI detailing practice.
How many profiles do I need for a typical window opening?
One 2.5 m profile covers most domestic window widths in a single length, which matters at 220 mm projection because any intermediate joint becomes visible on the deep trim face. Measure the opening width and add 30–50 mm overhang each side past the reveal. For openings wider than 2.5 m clear, two profiles join with a manufacturer-approved jointing strip, so plan the joint to fall away from the visual centre of the opening.
Do end caps come included?
End caps are sold separately as a matched pair, allowing precise pairing with the cut profile width. Order the white end-cap pair alongside the oversill so the matched components arrive together, since one pair closes both ends of a single oversill run.
Can the 220 mm oversill be cut to length on site?
Yes, each 2.5 m profile is designed to be cut to the measured window width on site using a fine-toothed metal-cutting blade. Leave 2–3 mm clearance at each end for the end cap to seat without forcing, then deburr the cut edge with fine-grit abrasive so the end-cap seal beds cleanly against the cut aluminium rather than catching on a rough edge.
Are there fixing implications at this projection depth?
At 220 mm projection the trim works structurally harder than shallower alternatives, and wind-uplift loading on south-westerly elevations facing prevailing UK weather should be verified against the project's exposure category. Standard 300 mm fixing centres along the upstand suit most sheltered and moderate-exposure sites, while supplementary mechanical fixings may be advisable on high-exposure facades — confirm against the project specification and any system-supplier guidance covering the build-up in use.
Why is this product self-collection only?
Powder-coated aluminium profiles of 2.5 m length dent too frequently in courier transit to remain economic on visible white trim, where handling marks show clearly against the brilliant white finish. Self-collection from our Southampton warehouse keeps the profile in factory condition through to install, which is the outcome that matters most on facade detailing visible for the service life of the EWI system.