Q. We have just read the HIP report on the house we have agreed to buy and discovered that the current vendors have built an extension over a public sewer, after making further checks we have discovered that the vendor never sought permission to build over the sewer from Thames Water prior to the build, where would we stand if we continued with the purchase?
A. This is indeed a serious problem. Public Sewers are often within the property boundary and in some instances – like yours run close to or underneath buildings. Building work can affect sewers and it is the water company’s responsibility to ensure that no damage is caused to them or restrictions placed on how they can access or maintain them. If necessary they have the right to stop any development works or – as in this case any building work that has been erected may be taken down if it was erected without permission. The Water Company would need to hear about any building work over or within 3 metres of a public sewer. This is necessary as increasing the weight above a sewer by constructing a new building may cause the sewer to collapse. A collapsed sewer can cause structural damage to the new building or extension or its foundation and may also interrupt drainage from surrounding properties. Should such a situation occur, the sewer would need to be repaired quickly and this may involve taking down the building constructed above it.