How can I find a stud?

[SmellsLikeWeenSpirits]

Or more specifically a rafter? Behind plaster board
There are no telltale nail marks. I can't hear anything when I knock. I've not got a stud locator.

I tried hammering in a nail at a few intervals. Didn't find it but have lots of holes

There must be a way surely?

How big a hole are you willing to make?

Knocking nails in wont help as you may have already hit the rafter and just not noticed.

If you can get above the wall (lift a floorboard above) poke a stick down and measure the distance.

Idea number 2. Get ANY MAGNET. It should be drawn to the metal content (a detector is just a magnet with a beeper)

It's the underside of the roof

Ah ha, I've got a wire and pipe detector. So that'll detect the nails where the plasterboard is held on? Yessssss

Yes, it's exactly the same device! just branded differently. You should know where your pipes are, and provided your wiring is in line with building code, it should be in a straight line either horizontally or vertically, from existing sockets and switches.

You'll get a beep every few inches as you encounter a nail... then it's a case of playing "dot to dot". How old is your house? are you sure it's not latte and plaster?

Latte and plaster??? I'm not sure coffee is an approved construction material

1920's ex local authority

The loft has been converted, so I'm pretty sure it'll be plasterboard

Can't get up there to try though as dp is asleep, but thank you, I have new hope

oh, if you're in the loft, then plasterboard... I spelt Lath and Plaster wrong. In 1930s-1950s housing, it gives you a lot of false positives as the quality wasn't good and they threw in lots of extra nails and staples to hold shorter scraps of wood together.

here I am.

And the other thing:

Once you have made one hole through the plaster, get a wire coathanger, bend it into a shallow curve, poke it through the hole, sideways, until it touches something. Mark the length you poked through, withdraw the coathanger, pencil the plaster at the same distance from the hole. Now repeat it to the other side. They will be about 18" to 24" apart.

I also sell the device ready-made at £99 plus P&P.

If you have a smartphone I think there's actually a detector app!

legarmpits I think that might be a different sort of stud

PigletJohn, I don't really want to make a hole in the plasterboard

The problem wit detecting the nails is that I know where the plasterboard is nailed on, but not where the particular rafter I need is, it's somewhere between the two lines of nails

there are usually nails wherever there is a rafter, so no nails suggests no rafter.

Even if say for example the rafters are 50cm a part and the plaster board 150 wide, would it be nailed down eAch side and down the middle too and so to all three rafters?

yes

you said you've put nails in and made holes. Why don't you want to drill a hole to find your rafter?

1 hole + polyfilla = 0 hole

Hmmm. The nail hols are teeny weeny, I had thought you meant a BIG HOLE, but I guess a no 6 drill bit would make a big enough hole to poke some wire through? And then a smudge of poly filler over yes?

6mm would probably do. Maybe 8mm would be more roomy. You can easily polyfilla a hole as big as your finger though, in a couple of layers or mixed with a scrap of loft insulation to stop it falling out.

Thanks PigletJohn I'll give it a go I think