The kind of walls you have matters, writes Jeff Howell. But finding out can be tricky
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Has your house got cavity walls? Or is it built with solid brickwork? Don't be embarrassed if you don't know the answer. Nine out of 10 home owners said they hadn't a clue.

The information should be in your mortgage valuation report but, hey, who bothers to read that? Like most of the documentation flying around during the house-buying trauma, it gets scanned or speed-read down to the bottom line - the one with the pounds sign - does the surveyor's valuation meet the asking price, and is the lender going to cough up?

No one can blame you for that. Buying and selling a home is the third most stressful thing that can happen to you, apparently, after divorce and redundancy, so, understandably, details about your external walls can appear as mere trifles in the wider scheme of things.

It may come as some comfort to know that even the anoraks who do read their survey reports can emerge none the wiser. Reports are written in such odd, vague terms that the effect can be like eating a marsh mallow - you remember your jaw going up and down, and the sensation of swallowing, but your stomach offers no evidence of having received any nutrition.

Similarly, surveyors' reports can leave a memory of having read something, but no signs of any information having been imparted. This is deliberate. If a surveyor's report contained any actual statements, then it would leave its writer open to legal challenge about their factual basis. And this could present a problem for the writer, and for the writer's professional indemnity insurance premiums. So, in the circumstances, surveyors concur that statements are best avoided. Appearances are OK, as in "The walls of the house appear to be built from brick", as are statements attributable to others, like, "The vendors inform us that the roof has been re-slated". And, of course, the many caveats, such as, "Inspection of the floors was not possible owing to the presence of fitted carpets throughout".

Anyway, don't let this put you off. It is important to know if your house has cavity walls, and it is a simple matter to find out. Go outside and look at the brickwork. Are the bricks all the same size and shape, and do they overlap each other by half their length? This pattern is called stretcher bond, and it means the brickwork is 100mm - or 4 inches - thick. We call this a half-brick wall, and it is usually the outer leaf of a cavity wall.

If, on the other hand, it looks as if there are half bricks distributed between the whole bricks, and the bricks overlap each other by a quarter of their length, then you've got Flemish bond or English bond, or some variant of these. What look like half bricks are actually whole bricks turned to run through the depth of the wall. This will be 215mm or 9 inches thick, and is known as a one-brick wall. It will usually be solid brickwork, with no cavity. If this is your house, you can relax.

If you answered yes to the stretcher bond question, though, you have one further test to carry out. Go back indoors and tap on the inside of the wall. If it sounds hollow, like a wooden box, then you're probably in a timber-framed house, more of which later. If it sounds and feels more solid, then you are, indeed, in a house with cavity walls. For details of how this will affect the rest of your life, see next week's column.