What's between plasterboard and the soil stack? All aspects of plumbing questions and answers, help, tips and information

[herbiehowler]

Hi
Trying to put up a small shelf above the wash basin. It's a hollow wall, but I seem to have gone through the plasterboard into something else, on both fixings. Don't want to hit the soil stack. Any suggestions?
Thanks

[Perry525]

That plasterboard is probably fixed (nailed/screwed) to some wood battens.
The trick is to find the battens with a metal detector.