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In general, it is always advisable to make a like-for-like replacement of types of window frame. In listed buildings, this will typically be required by the planning department anyway, particularly in the case of timber frames. However, steel frames can be potentially replaced by aluminium.

Ultimately, in any building, the choice of windows and the schedule for replacement and maintenance involves a choice between short-term gain and long-term pain. There will always be a temptation for those responsible to plump for the lowest outlay on hardware. But in almost every case, this will create serious maintenance costs in the future. For example, a PVCu frame may be many thousands of pounds less than steel up front; but it will require ongoing work and replacement in the relatively near future. Steel windows, on the other hand, require a larger up-front installation cost, but the design life is longer (circa 60 years) reducing the ongoing maintenance and replacement costs.

Scaffolding is another major factor here. Irrespective of the type of window, erecting scaffolding around a large apartment block can incur significant expenditure. If painting is required every few years, that's a huge extra investment. If, on the other hand, none is required, it may even be possible to extend the time between maintenance cycles on the rest of the property, saving yet more money in the process. This is a particular issue to be considered when deciding on the finish of the new windows. For example, modern steel and aluminium replacement windows have a factory or Polyester Powder Coating (PPC) that does not require regular painting. Timber windows can also come with a factory finish that will not need painting for some years.

Windows in listed buildings before and after (below) repair

the existing windows are beyond practical (not just economic) repair. In the next issue of Flat Living, we will provide further advice on the repair strategy for historic windows.

Practical complications of replacement There is a huge upside to getting the strategy for window replacements right. But the process of changing, replacing and maintaining them is fraught with issues. For a start it is important to grasp the differences between the four standard types of frame, as each has a significant effect in terms of look, cost and ongoing maintenance.

Timber: The oldest and often the most visually appealing material. However the downside is that it requires regular maintenance, including a repaint typically every six years. Timber deteriorates over time, but an area of rot isn't terminal and incremental repair is sometimes an option. Timber windows will often be a feature of

Issue 20

listed buildings, and one the planning department will want to protect.

Steel: The most expensive and robust, steel frames are designed to last for more than 50 years and often come with a polyester coating that lasts for 25 years and the up-front cost can be offset by a minimal maintenance regime. Steel windows are often seen in listed buildings, particularly the common Crittal windows, in use since the 1930s.

Aluminium: Mid-range in cost terms, aluminium looks like steel; so much so that it is often used to replicate it to keep budgets down. It is cheaper to maintain than timber, but requires more ongoing work than steel.

Plastic PVCu: Appealing for its being by far the cheapest option but the considerable downside is that it can look cheap is thick in profile, has a short lifespan and negative environmental impact. For this reason, PVC windows will be seldom seen in listed buildings.


Stained glass windows: These constitute a separate category all of their own. Planning departments will almost certainly want to preserve stained glass in listed buildings, even

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