Jeff Howell outlines some basics
concerning the maintenance of a brick built house.
Visit ask-jeff.co.uk - by Jeff Howell, builder, writer, and Sunday Telegraph columnist
Brick walls are one of the mainstays of building construction down the ages. The historical principle is simple. If you lived in a part of the world where there were a lot of trees (which included most of Britain until the sixteenth century) then you built your walls with wood. If there was no wood but you had access to broken stone, then you built your walls with stone. If you didn't have either of those, then it was probably because you lived on clay, as in most of central and southern England and the Low Countries. These areas have a history of building with raw earth, and many examples survive, such as the cob houses of the West Country and the clay lump buildings of East Anglia.
But it had been known since Greek and Roman times that if you fired the clay in a kiln then you got a more hardwearing material. At first this was used only to make clay roof tiles, but as kiln techniques got more sophisticated it became possible to produce large quantities of burnt clay bricks. After the Great Fire of 1666, the London Building Acts (of parliament) required all new buildings to have brick walls.
Brick construction reached its peak in the eighteenth and nineteenth centuries, and many of the surviving brick terraced houses that still make up around 50 percent of our housing stock were built with a skill and attention to detail that we will never see again. The twentieth century saw the introduction of the cavity wall, first built with two leaves of brickwork connected by wrought iron ties, and later with an inner leaf of various types of lightweight concrete blocks. These are referred to by lay-people as "breeze blocks" but are actually made from aerated pulverised fuel ash (PFA). God knows how many banned toxic waste materials will be discovered in them in years to come.
The last 20 years has seen the introduction of insulation materials into the cavity. This has made the building of brick walls ever more difficult, and, coinciding with a drastic reduction in the availability of skilled bricklayers, means that modern brick houses are usually built very badly. So, whilst a Victorian brick-built house remains a sound investment, one built since WWII may be hosting many problems.
Older brick houses are often spoiled by having the surface of the mortar joints (the "pointing") replaced with sand-and- cement. This is much harder than the original sand-and-lime mortar, and can cause many problems. If there is any movement in the brickwork then the new pointing will be unable to move with it, and this can result in cracking damage to the bricks; and because sand-and-cement is impermeable to moisture, the mortar will be unable to breathe, concentrating moisture evaporation in the bricks, which may then lose their faces through frost damage or salt crystallisation. Damaging repointing is a classic example of misunderstanding the nature of traditional building materials. Our forbears understood that the pointing between the bricks was a sacrificial material, which served its purpose by being gradually worn away, and would be replaced every half century or so. But today, when surveyors or builders see weathered pointing, they see it as a defect, and think it would be better to replace it with a more hard-wearing material.
Lime mortar is easy to make and use. The only problem is trying to find a bricklayer prepared to use it. There is a common myth amongst builders that lime and sand mortar will not harden unless cement is mixed into it, and a common myth amongst building conservation experts (who really should know better) that the only suitable material is hydraulic lime. In fact, hydrated lime - available in 25 kilo sacks (costing 3 to 4 quid)from practically every builders' merchants in the land - makes a perfect lime mortar for bricklaying and pointing. Mix it with washed coarse sharp sand, around 1 part lime to 4 of sand. Keep it wet in tubs or buckets, with an inch of water on top of it, and it will be ready to use whenever you need it. No need for expensive tubs of slaked lime putty, or expensive sacks of hydraulic lime. And definitely no need for cement.
Another common problem with old brickwork is the application of external masonry paints or textured coatings. These may sound like a good idea, as they offer the promise of long-term waterproofing of the walls. What the salesmen do not point out, however, is that many dampness problems are caused by water vapour produced inside the house, and the coating will have the effect of trapping this moisture in the walls. Also, if the paint or coating cracks, then rainwater will be able to get in, and will then be trapped behind it.
The good news is that paints and coatings can be removed using chemical methods. There are several different types, that respond to different strippers. All are painted on with a brush, and washed off with water. Call Strippers Paint Removers (01787 371524) for advice.
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