They purchase a property cheap, perform necessary works and sell it again at a profit. It is generally believed that they are motivated by simple business interests, but this is wrong. The reason they do it is so that they can smash up the sinks.
As soon as they get hold of the deeds they arrive in their van outside the selected property. Under the guise of intending to carry out "major improvements" they enter the house and gleefully head for the kitchen. What they are looking for, and usually find, is a Belfast sink. Many old houses have these ancient but fine-looking sinks in the kitchen. They go back to the days when washing was done by hand. They are made of glazed white china, are deep, sturdy and, in their own way, attractive.
But builders hate them. What builders like are shapely sinks made from stainless steel, with ready-fitted taps. They are quick and easy to install. Belfast sinks, on the other hand, represent the days of hardship in the building trade when people got bad backs lifting them, and taps had to be plumbed in with lead. They won't be happy until all Belfast sinks have been destroyed.
The whole thing has become an obsession, a ritual even. They disconnect the taps, then three of them drag the sink out into the front garden where they lay into it with sledgehammers. Only when it lies in broken pieces before them do they know contentment. They load the bits into a skip and go for a cup of tea.
They don't care that there are thousands of people who would gladly provide homes for these sinks, and pay money for them, as they are ideal for growing plants in. Nothing looks nicer than a few geraniums growing out of a Belfast sink set outside the back door. I'm not thinking of myself, I've already got three sinks and that's enough for anyone. I'm thinking of those who have never had a Belfast sink, and whose children will never see one, all because of these builders.
I once approached a builder who had just finished smashing up a sink and told him I would have given him pounds 50 for it. "Too late mate,'' he said with satisfaction, and went and sat in the van with his flask.