Should you still be determined to scrap a perfectly good boiler anyway, for whatever misguided reason, then that is your own choice. The advice of your “fitters” is wrong, though. They would no doubt prefer the simplicity of fitting a new boiler with a balanced flue, which requires it to be fixed against an outside wall. However, Kidd boilers are floor-standing and use conventional flues (although they are generally specified only for larger houses, because they are too big to fit inside a modern kitchen cupboard unit).  There are also several models of wall-mounted modern condensing boiler (including those from Worcester Bosch and Viessmann), which could be sited in the same location as your current boiler. These use flexible PVC flue liners in continuous lengths that can be pushed up existing flues and chimneys, thus getting around the problem of having to provide inspection hatches for concealed flue joints.  Q Reinforced concrete appears to incorporate rusty steel, which must eventually attack the concrete. Hence garden fence posts, etc, seem to disintegrate after only a few years. How is this problem overcome in major building projects?  A It is not true that reinforced concrete is made using “rusty” steel. You might have seen reinforcing bars (“rebars” in trade parlance) that appear to be rusty, but this will only be a thin surface staining. When the steel is surrounded by fresh concrete, the alkalinity of the cement stops it from corroding. As long as the finished reinforced concrete structure is protected from the elements, that’s the way things will stay.  The reason reinforced concrete fence posts, lamp-posts and park benches fail is because they are exposed to rainwater. The rain absorbs carbon dioxide from the atmosphere as it falls, thus becoming weak carbonic acid. This soaks into the surface of the concrete and, over the years, this acidity neutralises the alkalinity of the cement and allows the steel to start corroding.  As the steel corrodes, it expands, pushing the face off the concrete and hastening the destruction.  This problem is now much better understood than previously, and steel reinforcement in exposed structures such as bridges is protected with epoxy resin coatings.  The Sunday Telegraph Guide to Looking After Your Property by Jeff Howell (Ebury £17) is available to order from Telegraph Books at £15 + £1.95 p & p.  Send your questions to Jeff at Property, The Daily Telegraph, 111 Buckingham Palace Road, London SW1W 0DT, or email askjeff@telegraph.co.uk.
Troubleshooter Jeff Howell warns against rushing to replace ageing   appliances, and gets to the heart of reinforced concrete