Studs and Plasterboard Walls - Cannot Find Studs to Fix Shelf to? Kitchens, doors, rails, stud, tables, chairs, stair cases, garden furniture etc... Find answers and ask questions here!

[Rincewindwiz]

Hi

I have an interior plasterboard wall separating the utility room from the lounge
On the LH side of the wall is the underside of the stairs. On the RH side is the boiler, a couple of electric switches and an external wall. The wall is about 7 feet wide.

I want to fix a shelf onto this wall but cannot find any studs to screw into.
I've tried the magnet approach - nothing
I have a cheap stud finder which finds studs but when I drill through the plasterboard there seems to be no wood. The drill goes in about 1.5 - 2cm and then no resistance at all.

Any other suggestions as to how I might find the studs?

[welsh brickie]

studs are usually set apart at 400mm centre to centre, try using a small drill bit and drill the wall where your positioning the shelf and drill in a straight line till you hit a stud