Locating ceiling joists to fix and screw plasterboard

[SparrowHawk99]

Before I just go out and buy a stud finder which could be hit and miss just wondering if there is an ingenious method of finding the centers of joists for screwing without making exploratory holes? A bradel springs to mind but still punctures through the existing board.

I'm keen not to make holes as will be double boarding on top of the existing with acoustic board. The house is around 200 years old so there is bound to be distortion and don't trust a line drawn with a straightedge at a guess

 

[loply]

Powerful magnets are the best way.

Just little ones about the size of a 20p coin but they stick to the screws/nails which are holding the boards to the joists.

You locate several screws/nails by sliding the magnet around and mark around them with a pencil, once you have several you know the line of the joist.

You also know the location of the nails/screws so you can avoid going in to them.

Electric stud finders are all useless, had loads of them from cheap to expensive not a single one worked reliably.

 

[SparrowHawk99]

Powerful magnets are the best way.

Just little ones about the size of a 20p coin but they stick to the screws/nails which are holding the boards to the joists.

You locate several screws/nails by sliding the magnet around and mark around them with a pencil, once you have several you know the line of the joist.

You also know the location of the nails/screws so you can avoid going in to them.

Electric stud finders are all useless, had loads of them from cheap to expensive not a single one worked reliably.

Shame I can't find any walk in stores, they only seem to be sold on the internet and I've got the board coming tomorrow! Damm it there's always something!

 

[conny]

If you or anyone in your family/friends have a pace maker fitted then please be very careful with/around these magnets.
They are VERY powerful and can cause problems for anyone with a pacemaker fitted.

THEY SHOULD NOT BE LEFT LYING AROUND!

Oh, and keep them away from your credit/debit cards and DVD's.

 

[Norcon]

Axminster supply tiny neodyniam magnets about 10mm diameter and are ideal.

Have a Bosch GMS 120 and its ok finding studs. Foil backed plaster board and its useless.

 

[conny]

Axminster supply tiny neodyniam magnets about 10mm diameter and are ideal.

Have a Bosch GMS 120 and its ok finding studs. Foil backed plaster board and its useless.

Thats the ones I was warning about.
Couldn't think of their name but it is Neodyniam. They should come with a health warning!
Thanks Norcon.

 

[Flyboytim]

Neodymium Nd alloy magnets.

Small magnets of this type can prove lethal if swallowed, especially by small children, and may be powerful enough to cause injury to adults if handled without caution.

Really strong magnets of this sort can be found in old hard disk drives, CD/DVD drives, and most earbud/plug type headphones. If you have any of these that are not working, destructive disassembly will allow you to get the magnets.

These little round magnets - easy to lose, take great care if you have small children around:
http://www.instructables.com/id/Powerful-magnets-from-earbuds-complete-extraction/

Similar magnets - often rectangular - found in mobile phones, bigger ones in some miniature speakers.

The strongest are commonly found in hard drives:
http://www.youtube.com/watch?v=liVHQA-vOu0

The design type and number of screws varies from drive to drive. Usually two magnets , occasionally only one are present.
These can pinch and split skin if they are allowed to snap together. There are often tiny Nd magnets that are used to brake the head mechanism in the disk drive too!

CD and DVD drives use powerful Nd magnets in the lens focussing assembly:

http://www.youtube.com/watch?v=RHj_BvRjQyU

Again, there are many designs, but all are similar. Stronger and larger magnets than earbuds, but still a swallowing danger.

 

[Blagard]

Powerful magnets are the best way.

Just little ones about the size of a 20p coin but they stick to the screws/nails which are holding the boards to the joists.

You locate several screws/nails by sliding the magnet around and mark around them with a pencil, once you have several you know the line of the joist.

You also know the location of the nails/screws so you can avoid going in to them.

Electric stud finders are all useless, had loads of them from cheap to expensive not a single one worked reliably.

I agree this works well when you find a fixing, but you have to be really very close before you get a "lock on". So I would suggest you start the "sweep" with the aid of plastic ruler or other guide and move along at maybe a cm or so at a time until you get a hit. Trying to find a fixing without method is really pot luck. Sort of battleships on the ceiling

 

[loply]

Powerful magnets are the best way.

Just little ones about the size of a 20p coin but they stick to the screws/nails which are holding the boards to the joists.

You locate several screws/nails by sliding the magnet around and mark around them with a pencil, once you have several you know the line of the joist.

You also know the location of the nails/screws so you can avoid going in to them.

Electric stud finders are all useless, had loads of them from cheap to expensive not a single one worked reliably.

I agree this works well when you find a fixing, but you have to be really very close before you get a "lock on". So I would suggest you start the "sweep" with the aid of plastic ruler or other guide and move along at maybe a cm or so at a time until you get a hit. Trying to find a fixing without method is really pot luck. Sort of battleships on the ceiling

It's all about the technique, and the size/power of the magnets

I suppose also about how many nails/screws they used for the boards.

As soon as you find one though it's real quick to find the others, usually only takes me 10-15 seconds to find one.

Need to wrap tape or something around the magnet to provide a 'hand hold' at the back, makes it easier to run it back and forth.

 

[dhutch]

When I re-boarded my three bedrooms I went into the attic, measured the spacing with a tape, located a single joist with a large nail/screw and then marked out the position of the others from that.

One room the where running at an bit of an angle, so took measurements at both ends, the other was near enough I just did one in the middle.

Draw the pattern out with a marker pen (its getting covered anyway) and then whacked the boards up. Missed about 3-4 times per room, which out of about 150 screws is good enough for me!

Like the magnet idea a lot however.

I also put a sheet of polythene up before the over-boarding rooms 2 and 3, staple gunned to the old board working from the middle outwards, as I wanted to board the loft and found I was getting condensation on the underside of the boards. Room one was later sealed with a paint on plasterboard sealant, which was then a pain to paint over it no longer too the paint the same way and needed three (much thinner) coats.



Daniel

 

[ban-all-sheds]

Powerful magnets are the best way.

Just little ones about the size of a 20p coin but they stick to the screws/nails which are holding the boards to the joists.

You locate several screws/nails by sliding the magnet around and mark around them with a pencil, once you have several you know the line of the joist.

You also know the location of the nails/screws so you can avoid going in to them.

Electric stud finders are all useless, had loads of them from cheap to expensive not a single one worked reliably.

I agree this works well when you find a fixing, but you have to be really very close before you get a "lock on". So I would suggest you start the "sweep" with the aid of plastic ruler or other guide and move along at maybe a cm or so at a time until you get a hit. Trying to find a fixing without method is really pot luck. Sort of battleships on the ceiling

It's all about the technique, and the size/power of the magnets

I suppose also about how many nails/screws they used for the boards.

As soon as you find one though it's real quick to find the others, usually only takes me 10-15 seconds to find one.

Need to wrap tape or something around the magnet to provide a 'hand hold' at the back, makes it easier to run it back and forth.

So if you were re- (not over-) boarding a ceiling, and really wanted to p**s people off, you could use non-magnetic screws/nails, and tape rows of washers to the boards between the joists...