Timber windows

Today’s high performance wood windows come double- or triple-glazed and pre-finished under factory controlled conditions. They carry some of the best warranties in the sector – typically 30-35 years for the frame and up to 10 years for the paint finish and glazing units. They provide a long-lasting, high quality product that enhances the value of a property, requires little maintenance and it is more simple to repair, has exceptional thermal performance, and the highest environmental credentials.

A wood window is an engineered product, designed and manufactured to withstand extremes of weather. For maximum durability and maintenance intervals, fit wood windows that have been fully painted or stained and glazed in the factory.

Energy efficiency

• This mainly depends on the glazing unit, although wood, as a good insulator, helps energy-efficiency by reducing ‘cold bridging’
• There are 2 ways to measure energy efficiency, U values & the British Fenestration Ratings Council’s (BFRC) Window Energy Ratings (WER)
• For new build, the average U value of all windows must be 2.2 or lower
• WER ratings range from A (best) to G based on performance, with higher ratings increasingly common


• Most insurance companies demand ground floor window locks
• Their security can be enhanced by using laminated glass
• Wood Window Alliance windows come with security ironmongery and comply with BS: 7950: 1997 for enhanced security

Choose the right style

The right window style makes a big difference to the look of a building and can enhance its value. Each different window type can present different styles, depending on the design of the glazing bars.

Modern methods of surface fixing timber glazing bars allow single double glazing units to be used without compromising the aesthetic features of traditional windows. This is important in in conservation buildings and areas.


Avoid projecting timber sills. Use stone, brick or tile sub-sills which allow the windows to be recessed to provide protection for the window and brickwork (now a requirement of Approved Document L of the Building Regulations). Stone sills should not be used in timber frame constructions.

Storage and Handling

• Check the delivery complies with the order and there’s no damage
• Where possible store windows upright in clean, dry and covered conditions
• If outside, stack on level bearers and cover with a tarpaulin; don’t use polythene as it can cause condensation
• Store in the sequence of use
• Use spacers between frames with projecting sills or hardware
• Don’t lift frames by their fittings.

Fitting windows

• Use durable packings between windows and the structure to avoid distortion to the frames when securing them. Position side fixings 150mm from top and bottom of the frame and at maximum 450mm centres. Add fixings to the head and sill for windows exceeding 1800mm in width, or two frames together
• Take care with packings to sash windows not to distort the sliding mechanism
• Damp proofing should be fitted in accordance with Building Regulations
• For fixing to the structure, and gap sealing, use specialized proprietary fixings and foams, in accordance with the manufacturer’s instructions.

Bespoke windows

• Bead glazing must be used with insulated glazed units
• When preparing and finishing, ensure surfaces, edges, and primer/base coats are in good condition
• On external surfaces, use a vapour permeable paint or a high build stain
• Second coats or undercoats must be applied to primed/base coated windows before exposure to the elements
• Fit double glazing units onto appropriate setting blocks (to protect against moisture ingress) with distance pieces whenever non-setting glazing compounds are specified
• Use only the recommended glazing materials in accordance with the manufacturer’s details.

Many manufacturers offer pre-glazed and factory-finished windows which meet independently assessed standards. One way to be sure, however, is to choose a quality mark window from the Wood Window Alliance, which claims a 60-year minimum estimated service life, and will:

• Meet the minimum standards set out in BS 644, or equivalent standards from other countries
• Meet the wind and weather resistance performance standards of BS 6375 Part 1
• Meet the minimum performance standards for operational aspects of BS 6375 Part 2, or equivalent standards from other countries
• Are accredited by an independent UK or European body to prove compliance with those standards
• Are manufactured from timber, sourced legally from sustainably managed forests
• Have service life warranties for durability, paint life, ironmongery, insulated glass units, weather seals and glazing materials
• Meet or better the UK Building Regulations recommendations for energy efficiency.

Resource from Wood Campus

Side hung casementSide_hung_casement

• The most common type; outward opening; 100% openable area
• Normal max w: 600mm, h: 1500mm
• Hinges attach sash directly to frame
• Available with different hinge mechanisms, some allowing window to be cleaned from inside.

Projecting top hung casementProjecting_top_hung_casement

• Popular in flats and medium to high rise buildings; 100% openable area
• ‘Topswing’ or ‘H-type’ hinge mechanism allows sash to rotate on outside of frame, for easy cleaning and painting
• The mechanism often incorporates an ‘espagnolette’ locking system and child safety locks which restrict opening to 100mm, but can be overridden.

Tilt and turnTilt_and_turn

• Popular in Europe, and increasingly in the UK; 100% openable area
• Tilts from bottom, allowing secure ventilation
• Turning the handle in the opposite direction opens window as a casement inside room
• Makes cleaning easy, useful if external shading, e.g. louvres, is required. Check with your client to ensure compatibility with curtains or blinds.

Vertical sliding sashVertical_sliding_sash

• Traditional type; 50% openable area
• Often required for older buildings and conservation projects where like-for-like replacements are required
• Both sashes open by sliding within frame
• Traditional lead counterweight needs space in sash box; modern spring counterweight compact
• External access required for redecoration and cleaning.

Pivot hungPivot_hung

• Popular in the ‘60s and ‘70s
• Simple centre pivot allows sash to turn through 180 degrees; 90% openable area
• Can conflict with curtains/sills and need restraint to prevent uncontrolled rotation.

Installation of a timber window
Installation of a timber window
Timber window frames
Timber window frames

European Wood (in China)
C412, Beijing Lufthansa Center
50 Liangmaqiao Road, Chaoyang District
Beijing, P.R. China 100125
T +86 10 6462 2066, F +86 10 6462 2067
Sino-European Wood Center
Room 202, Engineering Department,
Taoliyuan Hou, Xuhui Campus of Jiaotong University,
No.655 Panyu Road, Xu Hui District, Shanghai