Rogues Gallery

These pictures show the tops of some very large chimneystacks. The white stuff looks a bit like snow but in fact it’s cement rendering. The installers have been faced with the difficulty — or impossibility — of putting a chimney lashing kit around a really big stack. To do this it is necessary to reach to all four corners of the chimney. If the roof is steep the outer edges of the stack can be well out of reach. Another problem is that a very long lashing wire has so much stretch in it that it can never be properly tightened. Chimney lashing kits are not intended for big stacks with dozens of pots.

None of this provides these installers with an adequate excuse. Fixing chimney kits to pots is very dangerous. Chimney brackets are designed to fit securely on a 90° corner. When fixed to a round chimney pot they are likely to twist sideways, leaving the mast and aerial at an angle where they can tip up the whole pot. Tightening a lashing wire around a pot imposes a massive strain. Chimney pots are heavy and when they break they have sharp points and jagged edges — not the sort of thing you’d want to hit you on the head.

So what should the installers have done? Masonry hiding under rendering is always suspect, because sometimes a chimney is rendered to save the expense of repairing it properly. However, if a wall will withstand the attentions of an energetic pneumatic hammer action SDS drill without disintegrating it is a safe bet that it will support a normal domestic TV aerial. Subject to that practical test, the installers should have fitted pairs of wall brackets to the side of the stack. With the two brackets a metre apart the installations would have been perfectly secure.

My thanks to David of London for these two photographs.

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