Plumbing

A trench in a 5yr new build concrete floor shows a large cavity near the exsisting drain

Anonymous user 23/02/2024 - 3.02 PM

I'm trying to work out if I should be worried. I recently have been looking to convert a downstairs toilet to a wet room. In the process of doing this a sink and wall were removed and a trench was dug into the concrete to allow a shower drain to join to the existing 4" pipe where the basin drain was. About 150mm down and near the drain, the trench broke through into thin air. There looks to be a cavity up to a foot deep by the drain. I'm going to measure properly and take some pictures as it just looks like bare earth below. Can't see any insulation, just some flimsy fibrous material. I have no idea how far the void stretches and am not sure if it's normal. Any advice would be most welcome! It's a 5yr old New build style house.