Inspecting for joists before holesaw for Downlights

[Jupiter01]

I need to install a few Downlights into an existing ceiling. I don’t have access above this ceiling.

I’ve seen a few different methods where you can poke a small hole in the ceiling and inspect for obstructing joists before cutting out hole for Downlight.

I recently pushed a small screwdriver in all directions but then realised that I was very close to a joist - after I cut the holesaw.

Is there a simple and sure way to do this?

Thanks in advance.

 

[sparkwright]

After poking a small hole with a bradawl where the downlighter centre will be, you then need to poke four small holes - each one in each 'corner' of where the edge of the circular downlight hole would be. And then, angle the bradawl in these four holes to check you are still well away from the joist.

 

[mcprinter]

Read recently somewhere.
Small hole in the ceiling. Right angled piece of wire/coat hanger.
In the hole and rotate to check clearance.

 

[big-all]

drum with a screwdriver handle and listen for tone
once you find a joist you will often find the next one at 350 gap or 400/406 centres unless truss rafters then 550 gaps and 600 centres but always a guess as odd sizes will give odd solutions off off joist positions

 

[Jackrae]

If you get a map-reading compass, (with a transparent base) and the plasterboard is fitted using steel screws you will be able to detect the fixing centres by scanning the compass across the ceiling (holes not required) Note that you will be viewing the compass needle through it's base.

 

[big-all]

Neodymium magnets can find screws or nails a couple off mm under the surface

 

[Jupiter01]

UPDATE: did these earlier today and this method worked very well. Thanks for all the suggestions.

 

[big-all]

thanks for the update much appreciated

 

[johnny2007]

Read recently somewhere.
Small hole in the ceiling. Right angled piece of wire/coat hanger.
In the hole and rotate to check clearance.

That's what i've always preferred.
I have laughed hard at electrician who drilled 9 holes for downlights, all perfectly aligned, only to find a nogging on the last hole.

 

[JohnD]

I sell a Special Tool for this work.

 

[Jupiter01]

UPDATE: with the painting and downlights in place