Discuss Them wooden things in the ceilings in the Electrical Forum area at ElectriciansForums.net

Chris

Regular EF Member
Messages
75
Location
Merseyside
Hi,

I feel over the past few years more people are moving towards recessed downlights, on new builds its easier as you can mark out while there is no ceiling and know where they will land. But when retrofitting i have a hard time missing all the joists, are those stud finders any good? Or does anyone have any advice/tricks to help with them?

Thanks
 

Rob

Control System Engineer
Electrician's Arms
Messages
2,741
Location
UK/USA
Tap with a hard object and you'll hear where the joists are.
 

Gavin John Hyde

Electrician's Arms
Messages
2,690
Location
Somerset
A 2 or 3mm drill bit is always useful. Find a joist and drill a hole. Maybe 3 small in all to find joist and its edges.
Building regs did(it may still do) give tables for 400, 450 and 600 mm spaced joists. And thickness of boards etc.
Measure out said gap and if its been built by a half sensible person you should find the next joist That gives you the spacing.
It will differ slightly around chimneys, stairs etc...
Most uk houses follow this spacing.
As above magnets can find the fixings. With a lot of older ceilings you can in right light see joists as the ceiling either side being slightly different.
 

Midwest

Electrician's Arms
Messages
11,676
Location
Oxfordshire
I use the above methods, and my trusty terminal bare blade terminal screwdriver, whose sole purpose is to find either side of joist. Then measure to next joist. It doesn’t locate noggins and metal pipes that might be in the way though.

I have a stud detector, and it’s of much use as a chocolate fire grate. I’ve heated the really expensive ones are ok.
 

littlespark

Electrician's Arms
Messages
2,495
Location
Scottish Borders
Never thought of using a magnet. Good idea.
Tapping and listening for a hollow is good but tricky in noisy environment or double thickness of plasterboard.

Modern builds are 400/ 450/ 600mm centres between joists, but the measurements never seem to land right.
 

Pete999

Mentor
Electrician's Arms
Messages
22,993
Location
Northampton
A 2 or 3mm drill bit is always useful. Find a joist and drill a hole. Maybe 3 small in all to find joist and its edges.
Building regs did(it may still do) give tables for 400, 450 and 600 mm spaced joists. And thickness of boards etc.
Measure out said gap and if its been built by a half sensible person you should find the next joist That gives you the spacing.
It will differ slightly around chimneys, stairs etc...
Most uk houses follow this spacing.
As above magnets can find the fixings. With a lot of older ceilings you can in right light see joists as the ceiling either side being slightly different.
Get hold of the plans for the building, should show how the joists are laid out, within reason.
 

Wilko

Electrician's Arms
Messages
5,490
Location
Berkshire
I too use a small drill, "find first joist and measure" method. If this doesn't come up trumps, I go to the Man Himself for guidance.

IMG_1363.jpg
 

Bellendian

Regular EF Member
Messages
224
Location
Gatwick
I always find that you either have to lift a strip of floorboards above, or remove a strip of plasterboard below, in order to drill joists and run cables through to new lights. So once you've done that you can see the joist spacings and drill for downlights accordingly.
Not sure how you guys are running the wires to 'join the dots' once youve drilled your downlight holes using the tap or magnet method?
 

Strima

Electrician's Arms
Messages
3,630
Location
St Neots
I guess.
 

buzzlightyear

please let me back in to the prison cell.
Electrician's Arms
Messages
6,982
Location
star command
My proferd way of doing it with stud finder and a drill bit and then go for it ,if it looks like a golf course tuff.
 

Midwest

Electrician's Arms
Messages
11,676
Location
Oxfordshire
I always find that you either have to lift a strip of floorboards above, or remove a strip of plasterboard below, in order to drill joists and run cables through to new lights. So once you've done that you can see the joist spacings and drill for downlights accordingly.
Not sure how you guys are running the wires to 'join the dots' once youve drilled your downlight holes using the tap or magnet method?
WiFi electrics, it’s the way to go. Ask Tesla.
 

Matthewd29

Regular EF Member
Messages
1,294
Location
Belfast
Get hold of the plans for the building, should show how the joists are laid out, within reason.
If only that were the case. Most shops I've worked in don't even have a plan of emergency lights or anything like it. It amazes me sometimes as soon as it's done they must just part company, I do a lot of work in the airport here and they don't have have a decent map of most areas!
 

SWD

Gender neutral
Electrician's Arms
Messages
5,925
Location
London
Lift the floor above, easy way to find the joists..........
 

naylorpd

Regular EF Member
Messages
54
Location
Baku, Azerbaijan
Get hold of the plans for the building, should show how the joists are laid out, within reason.
Optimistic - on my newbuild house the developer won't give me any plans at all. I'm having to work it out for myself. I use a FLIR thermal camera to work out where the pipes for the heating system are and the dabs of plaster that fix the plasterboard walls (they're colder than the rest of the wall). I haven't had to work on joists yet.
 

leo79

Electrician's Arms
Messages
72
Location
1
As others have said, tap the ceiling, small drill bit, lift floorboards. I always make sure spots are evenly spaced out and alignment is spot on.
Bathroom fitter I used to do work for used to cut the holes out before we got there and he would literally eye it up and just drill random holes. Never hit a joist and customer always chuffed to bits with the bathroom.
Makes you wonder if sometimes we go a bit over the top with setting out.
 

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