Fixing and buying guide
VELUX GGL MK04 306621U Centre Pivot, Electric, Pine Lacquered, Triple Glazed 66 Pane Window, 78cm x 98cm
Who this product is for
This window suits homeowners and builders undertaking loft conversions, attic renovations, or upper-storey extensions where roof-mounted glazing is required. The electric operation makes it ideal for windows positioned high on the roof or in locations difficult to reach manually. Triple glazing and thermal performance meet current Building Regulations for new builds and major renovations across the UK. The MK04 size is particularly popular for standard domestic pitched roofs with rafter centres of 550mm to 900mm.
- Loft conversions and attic rooms
- High-level roof positions requiring electric operation
- Properties requiring enhanced thermal and acoustic insulation
- Standard domestic pitched roof installations
Compatibility and sizing
The MK04 is VELUX's fourth-largest standard roof window size, measuring 780mm wide by 980mm high externally. Verify your rafter spacing and roof pitch before ordering; this size suits most domestic pitched roofs but requires adequate structural support. The centre pivot mechanism allows the window to open inward from the middle, providing safe access for cleaning and maintenance. Electric operation requires a 230V power supply routed to the window location during installation. Ensure your roof structure can accommodate the flashing kit and that sufficient headroom exists below for safe operation.
- External dimensions: 780mm (W) x 980mm (H)
- Centre pivot opening mechanism
- Requires 230V mains electricity supply
- Compatible with standard UK domestic pitched roofs
- Check rafter spacing and roof pitch compatibility before purchase
What is included and pre-installation checks
The GGL MK04 306621U is supplied as a complete window unit with the pine lacquered frame, triple-glazed pane assembly, and electric motor mechanism. You will need to purchase the appropriate flashing kit separately to suit your roof covering type (slate, tile, or felt) and rafter depth. Before installation, confirm that your roof structure is sound, rafters are correctly spaced, and the opening has been accurately cut to size. Verify electrical supply is available and plan the cable route from the consumer unit. Check that the window opening is square and level; any deviation will affect operation and weatherproofing. Inspect the unit on delivery for transport damage and ensure all components are present.
- Complete window unit with electric motor supplied
- Flashing kit must be purchased separately to match your roof type
- Roof opening must be accurately cut to MK04 dimensions
- 230V power supply must be available at installation location
- Inspect for damage and verify all parts present on delivery
- Confirm roof structure is sound and rafters are level and square
Fixing and installation overview
Installation requires careful positioning within the prepared roof opening, with the window frame secured to the rafters using the supplied brackets. The flashing kit must be fitted before the window to ensure proper weatherproofing and prevent water ingress. Electric wiring should be installed by a qualified electrician to ensure compliance with Building Regulations and safety standards. The triple glazing and sealed unit are factory-assembled; do not attempt to disassemble or repair the glazing on site. Allow adequate time for proper installation and testing of the electric mechanism before handover. Refer to VELUX's detailed installation instructions and consult a qualified roofer or surveyor if you are uncertain about any aspect of the fitting process.
- Secure frame to rafters using supplied brackets
- Install flashing kit before window to ensure weatherproofing
- Arrange qualified electrician for 230V power connection
- Do not disassemble or repair the triple-glazed unit
- Test electric operation thoroughly before completion
- Follow VELUX installation instructions and Building Regulations