Why old buildings need to breathe

Why old buildings need to breathe

Spending three days talking and lecturing at the National Home Improvement Show made me again realise the huge importance of getting across the message that old buildings need to ‘breathe’. Many people simply don’t understand that using the wrong materials can be an expensive mistake which may wreck their home.

The way old buildings work is incredibly simple and, when I say ‘old’, I’m not just talking about ancient structures but virtually all buildings with solid walls – these include Victorian and Edwardian homes.

What has to be understood is that the modern building techniques that we know today began to be introduced in the second half of the nineteenth century and that cement based mortars, renders and plasters only came into general use by the late 1940s. These techniques rely on impervious outer layers, cavity walls and barriers against moisture – such systems are totally incompatible with traditional solid walls which work in a very different way.

In solid walled, old buildings, the bricks and stones were generally bonded with weak and porous mortars made of lime and sand. Where external walls constructed with these materials, and others such as ‘cob’ (earth), were rendered, lime render was used and this was often limewashed so the structure was able to ‘breathe’. When it rained, moisture was absorbed a few millimetres into the external surface but was able to evaporate when the rain stopped, helped by the drying effects of the sun and wind.

Inside, walls were plastered with lime and finished with simple breathable paints. Any excess internal humidity from washing, cooking and human activity, was dispersed via open flues and draughts, or absorbed by the breathable surfaces. In addition, a kitchen range and open fires burnt from autumn until spring, drawing air through the home and keeping internal surfaces at a steady temperature. Provided the building was maintained, the structure remained essentially dry.

In recent times the understanding of how traditional solid walls work has become confused and builders have tried to apply modern techniques to breathing structures. Cement renders, along with ‘plastic’ paints, waterproof sealants, damp proof membranes and even insulation materials can act as a barrier to the building’s natural ability to breathe. This is where the trouble occurs: the mix of technologies traps water within porous materials and exacerbates the very problems that they are trying to resolve.

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Renovation tale – Part 1

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This is the tale of my first major renovation project some years ago…

On the table is the surveyor’s report; yellow Post-it notes stick from its pages in such profusion that they no longer have any relevance. Phrases like “needs attention”, “must be thoroughly overhauled” and “a fair amount of dampness” are highlighted by marker pen with a frequency that ensures the eye goes instead to the few innocuous words left in the white spaces in-between.

This, I suppose, is what buying a 1900 terraced house is all about especially when its been lived in by an elderly tenant who has had to make do with an outside loo, a lethal looking gas fire and ceilings which may collapse at any moment. I’m thinking that no sane person would have parted with a considerable sum of money to buy such a place but then I know I’m not alone – others have succumbed to the temptation of crumbling plaster and damp.

“Look at the mould on this wall… the windows are rotten… you know it’s going to cost a bomb to do up.” This was the commentary the young and inexperienced estate agent gave as he first showed me round having clearly never been in the house before.

“Oh, aggh, help!” was the cry of my friend Linda some months later when her not very high heel punctured one of the floorboards in the hall and became stuck amongst the powdery gnawings of the woodworm.

My goal is not just to put right the wrongs of years but to subtly pull the house into the present so that it can work as a home yet retain the fabric of the past. I know it’s a difficult balancing act and that’s why I’ve decided to consult an architect. When we meet I feel I’m being psychoanalysed as he seems keen to know the most intimate details of my life but he assures me “It’s all about making the house and the person work together.”

The architect has been and gone. I am now waiting for a structural engineer and for a few moments I admire my striped deckchair and decide it looks rather smart amongst the general decay. As is the case with so many homeowners my mortgage company is insisting on damp proof courses and chemical treatments. I believe, like a lot of the experts, that this is unnecessary and that there is a much more holistic approach: cure the cause – be it soil banked up against a wall or a leaking downpipe – and the problem will go away. What’s more a great deal of money will have been saved and damage to the building avoided.

Frenzied raps of the doorknocker reverberate through the empty rooms. In an anorak that looks as though it has been in worse places than this, the engineer arrives and begins a slow process of prodding walls and sucking teeth in a way that quite clearly says all is not well. He draws expensive looking designs in his notebook. His main concern is that the flank wall – mine is an end of terrace – will not fall out and that a corner, where I intend taking out a chimney breast, does not collapse at the first hammer blow. As he leaves he promises to discuss “the problems” with the architect.

I return to the surveyor’s report and notice that in one of the white spaces are the words “the house is built in solid brickwork”. It is a strangely reassuring statement.

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