Discuss Best method to find joists ? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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L

Lofty

Ok, so you have a customer who's ceilings are boarded using foil backed plasterboard which effectively screws a lot of the electronic detectors and they DO NOT want loads of holes made in it so that 'it looks like a second-hand dart board'. What's the best way of locating the joists so they can have downlighters fitted ?.:confused:
 
Hi Cirrus,
Could do. But they have laminate flooring up there. So I suppose they either pay us to do it or they do it themselves and we come back.

Best regards,
Lofty
 
Could try tapping on the ceiling with a screwdriver handle, I know it's primative but the tone changes when you hit a joist. Sorry best I can do this time of night.:eek:
 
I normally tap the ceiling with the knuckle of my index finger and listen to the sound it makes. When it becomes a dull thud instead of a hollow noise you've found or are pretty near to the joist.

I use a laser line fixed to the ceiling to mark out the positions of the downlights, fixing it in a position to give suitable clearance away from the joist. I then make a pilot hole where the centre of the downlight is going to be and then stick a wire from a coat-hanger into the hole pointing it in four directions to make sure the joist is far enough away.
 
I like the laser idea, keep 'em nice and straight. btw if ever you can't find a cable in a downlighter hole when the plasterers have chucked everything out of sight, try sticking your mobile phone up there and take some pics...works a treat!
 
Actually did it using the knuckle method and my laser line. Took some time but victorious in the end. Mind you the plumber wasn't happy about having the radio off so we could here the different 'tones'.
 
Once you have found 2-3 and worked out the "Spacing" etc it should be easier.

I have seen a very unusual method a few years ago !!
the plasterboard was held up with nails. this guy using some timber went around banging the ceiling until the little bits of plaster fell off the nails !!!. I must admit he did a good job and it took him very little time to make good after (decorator painting anyway)
 
nice thinking with the nails and the mobile phone and the wire to check for clearance from the pilot hole

arent laser lines ace!

i want an endoscope they look brilliant and you can check out your own poop chute or a friends:p
 
could put it on the van underneath fault finding and above rewires endoscopys? endoscopies? bum inspections??

hahah lol sorry im a kid but not from brighton how dare you!!

im a good welsh lad :)

and that means im tight(with money) and if im gonna buy something im gonna exploit all its uses now bend over free inspections for all forum members luke is paying.. and first up! he requested on pm!!
 
Last edited by a moderator:
wot about the old faithfull tool, the spreads hammer, it wont find where the joists are, just a lot of places where they are not!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
I use a rare earth magnet, you can get them on Ebay. It is only the size of a 2 pound coin but very very strong. Use it to find the nails or screws in one joist and push in a board pin then the next joist and then you can work out the spacing of the joists.

You can also drop it in a paper or plastic coffee cup that has been left on a metal surface and laugh your arse of when your mate trys to pick it up.
 
They are normally 16" or 400mm centres if load bearing(floor above)

Sometimes 18" if not load bearing, upstairs ceiling etc..
 
i use a dewalt self levelling one. does horizontal and vertical and shines for miles and miles and miles and miles and miles, proper good, not cheap but you pays your money you get what you pay for!!
 

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