Costs: Doors & Windows

The term fenestration includes all of the apertures in your external building envelope that admit daylight, namely windows, doors, rooflights and any large glazed screens.

Historically, fenestration and joinery products were always timber, but technological advances and manufacturing improvements now mean that the range of options has grown considerably.

Finished products are now available in different types of plastic, medium/high density composite boards and metal laminates as well as natural timber.

How much do external doors and windows cost?

When undertaking a cost appraisal exercise you may find that, for seemingly comparable windows and doors, the priciest can cost two or three times more than the cheapest.

Typical costs Unglazed treated softwood timber windows will start at around £150 per m² for the frames. You should add another £50 per m² or so for the doubled glazed section(s) and then another £30 per m² for their decoration following installation.

Prices will obviously vary massively based on the size of your order and the complexity of the window designs.

By comparison, a fully glazed and decorated Scandinavian-style softwood window will cost about £300 – £350 per m² and will usually carry a 10 year warranty on the glass units and five for the decoration.

Add an additional £50 per m² to have an aluminium cladding on the exterior and another £50 per m² for super insulated glass.

PVCu windows can start from £150 per m² for a fully glazed unit with a premium on top where colours are introduced.

How much do glass walls and roofs cost?

Structural glass and folding sliding doors are really popular, and it’s becoming quite a competitive market place now as manufacturers launch offers to rival each other. Depending on their size and specification, the cost of this type of door can vary from £2,000 up to £10,000.

The structural glass is not so easy to price as it will usually be designed first in terms of span and load and then costed once the nuances of your design have been determined.

But as an indication, self spanning glass for a typical glazed box extension, including structural supports, is likely to cost somewhere between £900 and £1,200 per m², for the overall glazed area (walls and roof).

How much do rooflights and roof lanterns cost?

Rooflights are commodity products and supply is dominated by several well-known manufacturers including Velux, which has very transparent pricing and many different options from which to choose.

As an attractive alternative, roof lanterns are becoming increasingly popular. These are normally installed in flat roof areas and flood light to internal stairwells, kitchens or other ground floor living spaces. Prices can start from around £1,500 right up to the cost of a conservatory.

How much do internal doors, frames and architraves cost?

An unpainted hollow-core flush leaf can cost from as little as £25. Add to this an un-primed lining set at £15, enough basic architrave for both sides at £10 and your ironmongery at another £10 and you could have a kit of parts priced at £60 for each door set.

With labour for installation adding another £60, and then £40 for decoration after that, the total cost for each internal door would be around £160.

By comparison it is also possible to buy ready-made internal doors sets which are pre-hung in their frames, complete with installed ironmongery and fully decorated.

Obviously these are more expensive and the increase in cost will also be exaggerated further as better quality materials are likely to be used, including real wood veneers often incorporating inlays and marquetry.

Before you buy

The following are some of the details that you should consider before purchasing external doors and windows:

Thermal performance

Most manufacturers will provide you with the U-value of their glass (as one measure of thermal performance) but you should also understand how the window as a whole will perform, which includes both the frame itself and the way the company recommend that the window is fitted.

Maintenance

Some wooden windows will be offered as ‘factory finished’ and will come with a decorative guarantee that is unlikely to be much more than five years.

Plastic and aluminium clad windows tend to offer longer periods before decorative maintenance is required but be careful about the deterioration risks from ultra violet with plastic.

Regular lubrication of hinge mechanisms and locks (especially friction hinges) is important and doing so will make a real difference. For the hard-to-reach areas, self-cleaning glass is a real luxury.

Security

Doors in particular will need five lever mortice locks to satisfy most insurance requirements and usually a key locking mechanism to the window handle is also specified.

Some doors and larger casement windows also offer an espaniolette mechanism whereby the handle operates two or three latches in the leading edge of the opening leaf.

Some windows have very elaborate features to increase night time ventilation while at the same time retaining appropriate security.

Acoustics and ventilation

If you are building in central urban locations, near main roads, railways or airports, then acoustic performance may be top of your list. Triple glazing is best for this, along with substituting permanent window trickle ventilators with a mechanical heat recovery system instead.

Photo: This solid engineered timber door is Secured by Design accredited. The FunkyFront door costs from £2,560