Part 4.  The consequences of the Victorian chimneys.

In the previous parts of this article we dealt with the older types of chimneys and their liners and the problems they caused.  While the inglenooks and the Georgian styles of construction are still remarkably trouble free, even today, the same cannot be said for the Victorian chimneys.  This was down to their use of cement instead of the lime putty favoured by the Georgians, and its vulnerability to acid attack.  Having explained the chemistry behind the problem we would now like to show how this has devastated so many chimneys.

Call in the Experts – Certified Chimney Sweeps

One point.  Many people on reading this will recognise that their chimneys do suffer from one or more of the problems listed in these articles, and will want to know just how badly their chimney is affected and what they should do about it.  The best thing to do is to call in a certified chimney sweep.  Get him to sweep the flue and ask him to advise you.  Certified chimney sweeps aren’t just good chimney sweeps, they also have an excellent knowledge base, so make sure you tap into that.

Why is Acid Attack Such a Problem?

At first glance, acid attack seems no biggie.  So the cement gets eaten away a bit.  So?  Well, it isn’t just a bit.  That acid can go right through the chimney.

Plus, it’s what the acid leaves behind.  As we explained, the cement is a base, and the reaction goes  ACID + BASE  >  SALT  +  WATER.

In short all the little grains of cement turn into grains of salt.  This leaves the cement with all the structural integrity of a stale digestive biscuit, and it means that any stress on the chimney can have disastrous results.

Bent Chimney Stacks

This is rather elegantly demonstrated on the tall Victorian chimneys that emerge from the roof at the gutter and extend upwards to terminate well above the crest of the roof.  Once you know what to look for with Victorian chimneys you will soon see that a large number are actually slightly curved, and on some the curve isn’t slight.  It’s considerable.

The effect is exactly as if the chimney has bent with the prevailing wind.  It hasn’t, of course, nor was it built that way. Instead the curve is caused by the prevailing wind chilling that side of the stack.   That causes that side to be colder, which means there is more internal condensation that side, and thus more acid attack.  When a grain of cement changes to a grain of salt, i.e. calcium sulphate, calcium nitrate, or calcium carbonate (aka chalk!) the salt particles are bigger than the cement ones and so the cement mortar expands and crumbles, and where the effect is at its worst the bricks are basically held together by sand and dust.

With the curved Victorian chimneys, the cold side has expanded more than the opposite side and the whole thing curves like a bimetallic strip when warmed.

To recap.

1. Victorian chimneys are badly affected by acid attack.
2. Possibly, you shouldn’t park your car under a curving chimney.
3. Call in a certified chimney sweep if you are concerned about your chimney.

Check out our articles in this Chimney Lining series:

1. Chimney Lining – Inglenooks
2. Chimney Lining – Georgian Chimneys
3. Chimneys and their liners – the Victorian Era
4. Chimney Lining – Victorian Chimneys
5. Chimney Lining – Acid Attack
6. Chimneys – Modern Design
7. Chimney Liner – Lining a Chimney

For more advice, or to book a chimney sweeping appointment please call us on 01223 964305 or email us at bookings@ablewightchimneyservices.co.uk