Q. I am interested in purchasing a home that was built in Cork in the 1970s. I have been told that the home had to be underpinned due to subsidence issues. I understand I am unlikely to be able to get insurance but it is the perfect home for me. A friend has suggested that the fact that it has been underpinned is a good thing.
A. There is no doubt that looking at old houses a few words come to mind that can strike fear into a would-be house buyer; rising damp, dry rot and of course our old archenemy, subsidence. But as we learn more about these engineering problems in terms of their cause and indeed their remedy we learn that in most cases they are surmountable, so let’s look at your particular case in a little more detail.
Subsidence is caused by a deterioration in the bearing capacity of the ground under your home. It could be that this ground wasn’t strong enough to begin with (eg clay) or, as is more likely, it could be as a result of an old leaking clay sewer. Clay sewers are built using a series of short clay pipes with socket ends that are merely pushed together. As these lengths of pipe are so short, and there are so many of them along the length of your sewer line, all it takes is for one to leak slightly (as there is no rubber seal) and the cycle of leakage, causing deterioration of the ground under the sewer, causing more leakage, causing more deterioration begins until the ground and sewer fail and the resultant uneven settlement of the building occurs where some parts are still on good ground whereas some parts are now settling in the poor damaged ground this causing cracks in the walls of your house.
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