{"product_id":"french-door-glass-sealed-unit-symmetric-pane","title":"French Door Glass Sealed Unit (Symmetric Pane)","description":"\n\u003cp class=\"pr-flagship__lede\"\u003e\u003cstrong\u003eThe replacement unit engineered specifically for French door apertures\u003c\/strong\u003e. A 28mm symmetric toughened double-glazed sealed unit (4mm toughened \/ 20mm argon cavity \/ 4mm toughened) sized for single-leaf French door panels — 600 to 900mm wide, 2050mm tall — with both faces toughened to BS EN 12150 to satisfy the Approved Document N critical-location requirement that applies to all door glazing below 1500mm.\u003c\/p\u003e\n\n\u003cp\u003eFrench doors are functionally different from patio doors: each leaf is a narrow single panel hinged at the side, opening outward (or inward) from a fixed frame, typically used as garden access from a living room or as a balcony door from a bedroom. The aperture geometry is narrow-and-tall (typically 3:1 ratio), and replacement units therefore need a different stock-size set from the wide-and-tall patio doors. This flagship handles the French-door-specific size range.\u003c\/p\u003e\n\n\u003ch2\u003eWhy symmetric, not asymmetric\u003c\/h2\u003e\n\u003cp\u003eFor French doors, symmetric 4-20-4 toughened construction is the cost-optimal correct spec for the typical residential application. Asymmetric stacks (e.g. 6mm outer \/ 4mm inner) add weight without meaningful safety or acoustic benefit at this aperture size. Acoustic-laminated outer is an upgrade for properties facing busy streets — covered as a configurator option — but for the default garden-access French door, symmetric toughened is the right call.\u003c\/p\u003e\n\n\u003cp\u003eBoth faces toughened means the unit satisfies critical-location requirements on both sides — important because French doors are routinely impacted from both directions (pets, children pushing the door, knocks during furniture moves). Single-face toughening leaves the non-toughened side as the safety weak point.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical specification\u003c\/h2\u003e\n\u003ctable class=\"pr-spec-table\"\u003e\n  \u003ctr\u003e\n\u003cth\u003eOverall thickness\u003c\/th\u003e\n\u003ctd\u003e28mm\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eBuild-up\u003c\/th\u003e\n\u003ctd\u003e4mm toughened \/ 20mm argon cavity \/ 4mm toughened\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eToughening standard\u003c\/th\u003e\n\u003ctd\u003eBS EN 12150-1 (heat treatment) + BS EN 12600 (impact)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eImpact classification (both faces)\u003c\/th\u003e\n\u003ctd\u003eClass 1(C)1 (pendulum drop, fall height 1200mm, no penetration)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eBreak pattern\u003c\/th\u003e\n\u003ctd\u003eGranular (small blunt cubes, low laceration risk)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eGas fill\u003c\/th\u003e\n\u003ctd\u003e90% argon (BS EN 1279-3)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (centre-pane, uncoated)\u003c\/th\u003e\n\u003ctd\u003e1.4 W\/m²K\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (with hard-coat low-E configured)\u003c\/th\u003e\n\u003ctd\u003e1.2 W\/m²K — configurable upgrade\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eg-value\u003c\/th\u003e\n\u003ctd\u003e0.72\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eLight transmittance\u003c\/th\u003e\n\u003ctd\u003e~80%\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eCritical-location compliance\u003c\/th\u003e\n\u003ctd\u003eApproved Document N, diagram 1 — door glazing below 1500mm requires Class 1(C)1 or laminated equivalent. This unit satisfies that across the full pane height.\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eStandards\u003c\/th\u003e\n\u003ctd\u003eBS EN 1279, BS EN 12150, BS EN 12600, BS 6206 (legacy reference), Approved Document N\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eWhere this unit is the right call\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReplacement of failed (misted, blown, water-ingressed) sealed units\u003c\/strong\u003e in existing French doors — PVCu, aluminium, or timber. The frame is usually fine; only the unit needs replacing.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGarden-access French doors from living rooms and kitchens\u003c\/strong\u003e — the standard UK domestic application. Symmetric toughened DG is the spec building inspectors expect.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBedroom-balcony French doors\u003c\/strong\u003e at first-floor level — where fall-from-height risk is mitigated by the Juliet-balustrade on the outside. The internal door glazing still needs critical-location safety glass.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePeriod-property French door replacement\u003c\/strong\u003e in Victorian \/ Edwardian terraces where original doors have been removed and modern frames fitted — this unit replaces the modern unit, not the original glazing.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBoutique commercial settings\u003c\/strong\u003e — small hotels, restaurants, cafes with French-door street frontage where the door glazing has failed.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eFor full-height patio and bi-fold doors (1500-2700mm wide), the \u003ca href=\"\/products\/patio-bi-fold-door-triple-glazed-unit\"\u003e\u003cstrong\u003ePatio \/ Bi-Fold Door Glass Unit (Triple Glazed) flagship\u003c\/strong\u003e\u003c\/a\u003e is the right spec. For composite door inserts (small panels in a solid composite door), see the \u003ca href=\"\/products\/composite-door-glass-insert-toughened-laminated\"\u003e\u003cstrong\u003eComposite Door Glass Insert flagship\u003c\/strong\u003e\u003c\/a\u003e. For French doors where overhead-glazing safety applies (rare — typically a fanlight above), specify the laminated variant in the configurator.\u003c\/p\u003e\n\n\u003ch2\u003eStock sizes — French-door-specific\u003c\/h2\u003e\n\u003cp\u003eFour UK-standard French-door stock sizes are listed below — all 2050mm tall to match the standard UK domestic French-door panel height:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e600 × 2050 mm — narrow French door (cottages, smaller terraces)\u003c\/li\u003e\n  \u003cli\u003e700 × 2050 mm — standard small French door leaf\u003c\/li\u003e\n  \u003cli\u003e800 × 2050 mm — most common French door leaf size\u003c\/li\u003e\n  \u003cli\u003e900 × 2050 mm — wider French door (modern PVCu, aluminium systems)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eDispatch 10-14 working days from order (toughening adds ~3 days vs the standard clear unit). Custom sizes — including doors with internal Georgian bar overlays, arched-top fanlight units, and bespoke heritage-replica fielded-pane builds — are priced via the \u003ca href=\"\/pages\/configure\"\u003e\u003cstrong\u003eonline glass configurator\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eDelivery:\u003c\/strong\u003e French door units at these dimensions fit standard pallet networks (5-7 day delivery) but require careful packaging — every order ships on a timber A-frame within a protective cardboard sleeve. Inspection on receipt before installer signs off is critical; toughened-pane chip damage in transit can develop into spontaneous breakage weeks later.\u003c\/p\u003e\n\n\u003ch2\u003eCertification and standards\u003c\/h2\u003e\n\u003cp\u003eEvery unit ships with: UKCA mark, BS EN 1279 Declaration of Performance, BS EN 12150 toughening stamp permanently etched in corners of both panes (visible at the rebate after fitting — hold a phone torch at low angle to find it), BS EN 12600 Class 1(C)1 impact certificate, and a critical-location compliance statement on request. Heat-soak testing (BS EN 14179) is available as an order option — useful for properties with previously-experienced spontaneous breakage of nearby toughened units.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003ch3\u003eDo I definitely need toughened both faces?\u003c\/h3\u003e\n\u003cp\u003eYes for compliance. Approved Document N requires that critical-location glazing (which all door glazing below 1500mm is) meets Class 1(C)1 or equivalent on the face that's accessible to impact. Both inside and outside faces of a French door are accessible. Building Control inspectors checking a notifiable installation will look at both sides. Specifying toughened both faces is the only compliant build for a replacement French-door unit.\u003c\/p\u003e\n\n\u003ch3\u003eWill it fit my existing French door rebate?\u003c\/h3\u003e\n\u003cp\u003eMost modern PVCu, aluminium, and timber French doors are designed for 24-28mm units. Send the existing unit thickness (gentle measurement at the corner where the seal is exposed) plus a frame profile photo to \u003ca href=\"\/pages\/contact-us\"\u003eour contact form\u003c\/a\u003e for compatibility confirmation. The most common rebate mismatch is between older 20mm-rebate doors (designed for thinner units) and the 28mm standard — those typically need re-rebating or unit downgrade to 24mm.\u003c\/p\u003e\n\n\u003ch3\u003eAcoustic — busy road frontage?\u003c\/h3\u003e\n\u003cp\u003eRw of this symmetric build is ~30 dB — modest. For French doors on busy streets (Inner London terraces, town-centre cottages), specify the asymmetric-acoustic variant in the configurator: 8.8mm acoustic-laminated outer + 4mm toughened inner takes Rw to ~38-40 dB. The PVB laminate also satisfies the critical-location requirement on the outer face, so safety + acoustic stack in one build.\u003c\/p\u003e\n\n\u003ch3\u003eLow-E upgrade — worth it?\u003c\/h3\u003e\n\u003cp\u003eFor garden-facing French doors that are open frequently in summer and well-shaded in winter, the U-value upgrade matters less. For north-facing or shaded French doors that stay closed most of the year, hard-coat low-E (Pilkington K) drops centre-pane U to ~1.2 W\/m²K — adds ~£15-25 to a typical 800 × 2050 unit. Hard-coat is essential because soft-coat planitherm doesn't survive the 620°C toughening temperature.\u003c\/p\u003e\n\n\u003ch3\u003eInternal Georgian bars — possible?\u003c\/h3\u003e\n\u003cp\u003eYes — internal Georgian bars (clip-on overlay bars inside and outside the unit with a matching spacer-bar grid inside the cavity) are configurable. For French doors with traditional fielded-glass aesthetics, specify the bar layout (typically 4-panel or 6-panel) at order. Lead time extends to ~14-21 working days.\u003c\/p\u003e\n\n\u003ch3\u003eToughened stamp — where is it?\u003c\/h3\u003e\n\u003cp\u003eEtched permanently on each pane, typically 20-30mm from one corner. Visible inside the rebate after fitting — hold a phone torch at a low angle to find it. The stamp reads \"TOUGHENED \/ BS EN 12150 \/ [manufacturer code]\". No stamp = not toughened — important to verify on delivery as the unit can't be reverse-checked once fitted.\u003c\/p\u003e\n\n\u003ch3\u003eWarranty?\u003c\/h3\u003e\n\u003cp\u003e10 years on edge-seal integrity (BS EN 1279-2). 10 years on argon retention to ≥80% of initial fill. Toughened pane integrity is manufacturer-lifetime warranty against in-stock defects; spontaneous NiS-inclusion breakage is excluded unless heat-soak testing is specified at order. Transit damage is covered for 14 days from delivery — photograph on receipt before signing off.\u003c\/p\u003e\n","brand":"Pane Relief","offers":[{"title":"600 × 2050 mm","offer_id":61853954179402,"sku":"DG-FRDR-600x2050","price":139.0,"currency_code":"GBP","in_stock":true},{"title":"700 × 2050 mm","offer_id":61853954212170,"sku":"DG-FRDR-700x2050","price":162.0,"currency_code":"GBP","in_stock":true},{"title":"800 × 2050 mm","offer_id":61853954244938,"sku":"DG-FRDR-800x2050","price":185.0,"currency_code":"GBP","in_stock":true},{"title":"900 × 2050 mm","offer_id":61853954277706,"sku":"DG-FRDR-900x2050","price":208.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0895\/3515\/2458\/files\/double-glazed-sealed-unit-igu-product-cutaway_fb170fa9-d400-49ea-b541-40aed200e642.webp?v=1779018551","url":"https:\/\/panerelief.co.uk\/products\/french-door-glass-sealed-unit-symmetric-pane","provider":"Pane Relief","version":"1.0","type":"link"}