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Dormer Windows

Loft dormer windows for space and character.

A dormer window is a vertical window projecting from a gable or sloping roof up to approximately two metres wide. Also know as cottage dormers they significantly to the useable head height and character of a loft room.

When designed in strategic places they significantly increase the area of useable/full-height loft space, such as by a bed, desk or en-suite. Small dormers are a lovely additon to a room, especially where there is a specific view over the local area to be gained and when sympatertically designed they enhance the appearance of a roof.

In essence adding a dormer window turns a loft into a more spacious and characterful room, and the window can be dressed more traditionally with curtains or vertical blinds. Compared with rooflights any noise from rain is less and glass tends to keep cleaner.

Do I Need Planning Permission

Dormer windows usually do not need planning permission.

Understand the potential within your loft. Book a FREE, no obligation assessment with our professional surveyor.

0800 505 3414

Since 2008 new rules allow dormers in loft conversions with no added permissions. There are some simple Permitted Development guidelines to ensure they are in keeping with the neighbourhood and not causing a problem for neighbours. We can quickly confirm all your options if you need clarification on the ruiles and want to know the cost of converting your loft, adding a dormer window or two.

Windows or Extension

A further benefit of cottage dormers is that they don't require the significant structural support (RSJ) and structural calculations that larger extensions (over 2 metres) do. Keeping to within 6 foot width (approximately 4.5ft internally) provides a significantly cheaper option to larger styles.

Types of Dormer Window

We create 'cottage' dormers of under 2 metres (approx.) wide in many styles. The key feature being the roof style of the dormer itself.

  • Flat Roof DormerFlat Roof
    The most popular dormer roof style has a flat or 'mono-pitched' roof as this allows for maximum head height without exceeding the ridgeline. Roof covering choice includes: mineral felt, lead or fibreglass-reinforced liquid plastic.
  • Dual Pitched Dormer RoofDual Pitch Roof
    This attractive style has two pitched roofs and a gable end. Due to pitch the dormer is set lower in the roof reducing potential head height. The design is suitable for both sloping roofs and hip-end roofs on the side of a semi-detached or detached house.
  • Hip End Dormer RoofHipped Roof
    Similar to the dual pitch roof except the sloping front (three sides). This is an attractive style requiring more complex construction than above.
  • Velux Prefabricated
    This is a hybrid design of vertical window and skylight within a ready made dormer frame. The benefits are maximum light into the room, good head height and modern style design.

When drawing up plans we discuss the options based on the height within the loft, roof type and house size.

Dormer Construction

Each dormer window is individually planned and constructed in accordance with architectural plans and building regulations. The windows are constructed by creating a timber frame based on the roof rafters in a staged process, which includes creation of the roof aperture, gable end, installation of glazing, cladding, insulation and inside boarding and plastering.

  1. Validate building plans - when working from building plans our teams we pay particular attention to ensure measurements and angles are accurate before construction begins.
  2. Roof aperture - support is required if the dormer width is to span several rafters. Timber reinforcement is used to bridge rafters above and below and create the dormer frame. Sections of roof rafter are then safely removed.
  3. Building the sides. Roof rafters on either side of the aperture provide a base for the dormer frame. A series of vertical timber uprights are bolted to these, becoming the dormer walls.
  4. Building the roof. The dormer roof design is specified within the building plans. If the dormer has an angled/pitched roof then rafters are joined at the apex against a ridge board. If building plans stipulate a flat roof then horizontal timbers form the dormer roof.
  5. Cladding. Cladding provides a waterproof skin to the bare timber frame. A waterproof breathable membrane is secured by horizontal lats and then lead, tiles or slates are fixed. If render is used then the walls are prepared.
  6. Roofing. The completed dormer frame has the roofing material applied:
    • flat roof roofing felt torched-on in layers to provide a waterproof skin, lead laid in sheets to allow for expansion and contraction, fibreglass & plastic roofing prepared and installed.
    • pitched roof tile or slate to match existing installed over waterproof membrane and lats.
  7. Insulation. 100mm foil backed insulation board to maximize heat retention within the loft area is integrated into the dormer timber walls and roof. 50mm foil backed board applied over this to ceiling.
  8. Windows. The dormer window frame and double glazing is then fitted to the gable end according to building regulations:
    • Sill is made perfectly square and horizontal using spirit level
    • Angle of jambs perfectly upright
    • Window frame secured to the dormer frame with fixings
    • Gaps around window edges filled and sealed with cement mortar mix
    • Test window for easy opening, locks, ease of operation
  9. Plasterboard. Plaster-boarding of internal wall of dormer over frame and insulation boards.
  10. Plastering and skimming. Double application of plaster to make surface ready for internal wall decoration.
  11. Decoration. If the dormers are a part of loft conversion then decoration will be completed at the same time as the loft area.
Eyebrow dormer window

Contact Us

Contact us to discuss your ideas on 0800 505 3414 and receive a free, no obligation fixed price quote. We convert lofts in Greater Manchester and we provide an Architectural Planning Service throughout the whole of the UK.

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Free loft assessment & fixed price quote

Services

Plans Only - All UK

Design and Build - Greater Manchester

Process

A phone call

Free Consultation

Initial Design Scheme

Submissions to Local Authority

Plans Approved