When we received the first call about this job, it was all a little tricky to pin down what was required. We simply found out that our client had had ongoing problems with flies and bad smells, which had been getting worse over the period of two years. We asked whether any survey work had been carried out previously, and received a CCTV survey and report – but while it was clear that the client had a real issue with the existing drainage system, installed when the building was constructed almost 15 years ago, the extent and cause were not apparent.
At this point we couldn’t give a quotation for a fix, but we could quote for further investigation work – involving drilling holes into the garage floor, to ascertain the construction of the ground floor slab, and finding out whether there was a void below it. Excavation within the driveway, on the line of what we thought was the drainage entering the property, confirmed the line and its depth. Upon excavating on the building line and exposing the drainage under the concrete lintel entering the building, we had the opportunity to view beneath the ground floor slab. It was at this point that the cause of the problems became clear, and we could identify what needed to be done to put it right.
In our collective 40 years’ experience, we had never seen such bad installation of drainage below a property that is also relatively new and had been passed by Building Control. There were dislodged pipes, pipes with no connection discharging directly below the floor into the void, pipes laid on blocks and bricks, road pins and duct tape used to secure pipes, and bellied runs (where the pipes sag through being not properly supported).
The void beneath the ground floor slab gave us enough space to carry out the remedial works, but as it qualified as confined space working, gas detectors, escape sets and forced air ventilation measures were used on site at all times. With the effluent discharge taken away, we removed all existing installed drainage and replaced with new pipework. Rails installed at one-metre centres through the building provided us with fixing points to hang all new pipe to line and at the correct level. Once we completed all remedial work under the building, with new chambers and the connection back to the main public sewer completed, we backfilled. We then replaced all lids with insert cover and frames, to match the existing surface.