house doctor Peter Fall looks into the mine workings of years gone by in the North East.
AS a surveyor, I always felt that you needed to spend a little more time than normal explaining to clients from the south how the perceived threat of their house falling into a mine shaft, was pretty unlikely.
Whenever you buy a property, one search you should have is into the mining records, to determine whether there is a risk of future problems.
The North East has been extensively mined for more than 500 years, so we have to expect that the searches will come back with some comment about previous workings. I’ve seen reports which explain that six seams had been worked beneath the house. Rarely do we find them with no recorded workings. But it’s not the number of seams that are the problem, it’s the depth and thickness of seams that were worked, coupled with when they were worked, that gives us a better understanding of the risk of any movement to the property.
The weakness of these searches is in the records. The records were collated by the National Coal Board and are now held by the Coal Authority, but their records only go back 150 years or so. They are based upon the NCB workings but they also include the records of the nationalised mines. A good thing about the NCB was they supplemented the records with bits and pieces of information they gathered when breaking out new seams or dropping new shafts. But it still leaves a number of very old workings that were never recorded, and they are the ones that bring the surprises.
Even though we no longer carry out deep mining in the North East, new open cast sites keep adding to our knowledge of the ancient workings.
So should we worry? On a scale of 1-10, it’s down at the less than level 1. Let’s think it through. Most of the big workings were to seams that are very deep. They may have been thick seams, but these seams are not great caverns waiting to collapse. As soon as the coal was removed the ground above was allowed to collapse into the seam. This happened quickly down at the low level, but any movement was gradual at the surface. The mining engineers were able to calculate just how gradual it would be and how much the surface would distort. So it is most unlikely that the surface will be distorted from a seam allowed to collapse 30-40 years ago.
There is a “however” in this and that is with the ancient workings. Some of these were quite small and shallow and they did leave a hole in the ground. Fortunately, they are so old we expect pretty much all of them to have collapsed by now, but we can never be certain because we don’t know where they all are.
Perhaps the workings that can give the most dramatic collapses are the shafts down to the seams. The shafts weren’t just to get the men down and coal out, they were also to get fresh air into the seams. There are a lot of them and the location of shafts can be a bit hit and miss.
While the NCB has good records of its own shafts, they didn’t just stumble across un-recorded shafts like they did with seams. It’s these unrecorded shafts that can be the nightmare. One family in Whitley Bay, when hanging some washing on the dining room radiator one night, realised that their patio had disappeared. A shaft three metres (10ft) in diameter had opened up three metres from their back wall.
There were no records of a shaft but this was an old one that had been capped off with baulks of timber. Over the years this timber had decayed until it gave way. The cap was about two metres (6ft) down so it hadn’t been evident to the builder or the farmer before them.
The collapsed shaft was capped with a new concrete top and the house was monitored for more than 12 months. It didn’t move. Not a pleasant experience, but at least no harm to the house. Selling it on, however, is a different kettle of fish, now the searches declare this shaft is beneath the barbecue.
Peter Fall is former president of the Royal Institution of Chartered Surveyors. He is managing director of Clear Building Survey, tel: 0800 072-9003 www.clearbuildingsurvey.co.uk
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