The main components of timber window are:

  • Timber.
  • Glaze.
  • Coating.
  • Hardware.
  • Sealing.
  • Aluminium cover (if chosen).


The timber

Usually timber windows and doors are made from finger-jointed pine beams. Finger-jointed pine beam is much more stable than solid pine beam, also it is cheaper. It is easy to buy because every supplier has a solid stock in the warehouse. The finger-jointed pine beam is standard timber for manufacturing timber windows because of its price, availability, stability, and timber characteristics. Fenestrum for production of timber windows and doors uses only imported finger-jointed pine beam because Baltic pine has too much resin in it, often is poorly dried and sometimes even changed its colour to blue. If timber windows are made from low quality timber the resin could come through the coating if the surface of window is heated by the sun (the windows in the southern side are at biggest risk). Timber windows that are made from timber which changed its colour (has blueness in it) could start decomposing from the inside. There will be no options to repair such window and it should be changed by a new one. Despite finger-jointed pine Fenestrum is also using solid pine beams, oak beams, meranti, eucalyptus and other timber for manufacturing. The windows can be made from almost every timber that can be bought in the market and which is suitable for timber windows. It is still important to remember that every timber has unique characteristics. Fenestrum specialists will always consult clients which timber will meet their requirements best.



Fenestrum accurately chooses the timber. For manufacturing Fenestrum chooses timber that does not have branch spots or other defects. Outer layer timber is radial cut. In the process of manufacturing it is treated with antiseptic and coated with a few layers. The glued timber is more stable than solid and is considered the best material for timber window production. The glued timber is made from three timber planks that are glued together. The timber splints are facing to the different sides. Because of these reasons’ timber windows made from glued finger-jointed pine are highly immune for sudden temperature drops and increases, high humidity and deformation. If compared with timber windows made from solid wood, timber windows made from glued finger-jointed pine beams are about 80 percent more durable and 40 percent stronger.



For Euro-type windows Fenestrum uses 40mm and 56mm, triple glazing with 2 selective coating coated glazes and warm TGI edge. For windows that are exported to the United Kingdom: sash spring, sash box, casement flush and casement stormproof Fenestrum uses 18mm and 24mm double-glazing with 1 selective-coating coated glaze. The gaps between the glazes are filled with argon gas. For better glaze isolation quality Fenestrum offers to use warm plastic TGI edge which comes in white, grey, and black colours. Glazes without warm TGI edge has a regular aluminium edge inside.



The glaze can be different depending on client’s needs:

  • Energy efficient glaze with selective coating.
  • Acoustic glaze.
  • Glaze with sunlight control.
  • “Safe” glaze (laminated, hardened or both).
  • Toned, satin, obscure glaze, glaze with stained glass imitation or even stained glass itself.



Impregnation, priming and coating of timber windows and doors are performing with Teknos materials. These materials go deep inside the timber and protects it from negative external effects such as rain, frost, and sunlight. Fenestrum offers wide choice of colours (RAL) and if client prefers can offer a two-tone painted window. Clients can choose a solid colour from RAL palette and a wide choice of transparent colours from Teknos colour palette.


Usually timber windows are:

  • Varnished with clear transparent varnish from both sides on purpose to see the timber texture. Fenestrum does not recommend using transparent varnish or any other transparent coating on outer side of the window because such coating is not resistant to sunlight, so it is not long-lasting.
  • Varnished and stained from the both sides on purpose to see the timber texture. This coating is not long lasting as it not resistant to sunlight. This is the reason why Fenestrum does not recommend using it on outer side of the window.
  • Painted with solid colour from both sides choosing the colour from RAL palette. This is the cheapest and most reliable solution because solid paint is resistant to sunlight and it takes much less time in painting process. This is the reason why such windows are cheaper than two-tone painted windows.
  • Painted with solid colour from the outside and varnished and/or varnished and stained from the inside. It is probably most popular choice of Fenestrum clients because they can see a natural timber texture from the inside, and this makes timber window look like a nice piece of furniture and interior accent. Window painted with solid colour from the outside is protected against sunlight. It is still good to know that light paints are more long-lasting than dark paints because dark paints absorb much more sunlight than reflects. This is the reason why dark colours fade more quickly.



The window hardware is basically all the mechanisms that are responsible for opening and operating the window. This mean that window’s durability, reliability, and comfort depend on its’ hardware. Fenestrum uses only high-end quality German hardware ROTO FRANK AG and G-U (Gretsch-Unitas). For sash spring and sash box windows Fenestrum uses best hardware options from Pickard, Mighton and Reddiseals which is delivered from United Kingdom. For casement flush and stormproof windows Fenestrum uses IPA hardware and if client demands Nicos3D hinges. All these hardware brands are worldwide well known.



Special rubber strip that are installed in whole window’s perimeter which seals the window when its closed and prevents cold and wind getting into the house called sealing. Fenestrum uses two or three sealing to its windows (78mm window – 2 sealing stripes, 100mm window – 3 sealing stripes). Fenestrum uses only well-known superior quality German sealing Schlegel and Deventer.



Aluminium covers

Fenestrum is proud for its timber windows and doors which are covered with aluminium covers from outside. Fenestrum uses German BUG aluminium covers which are exceptionally durable resistant to any environmental impact and easy to care. Fenestrum also uses Guttmann aluminium covers on demand.



If client chooses timber windows covered with aluminium covers, there will be no need to worry about restauration of the window. Aluminium covers protect outer part of the window from mechanical damages and environmental impacts, such as sun, rain, snow, and cold breeze. Because of special aluminium cover fastening to the timber frame it let the timber to breathe and that prevents it from rotting. Fenestrum can assure that aluminium covered timber window will last 70 years and even longer.