locating joists in lath and plaster ceiling

[amandaeb]

Hello

I've been reading the archive posts about plasterboarding over old lath and plaster ceilings versus pulling them down and then plaster boarding.

A chunk of ceiling in the bedroom has fallen down, approx 4'x3', caused I guess by steaming off the wall paper. The dust this chunk has created is more than I ever imagined possible! So I think I'd rather plasterboard over the top. I wondered if anyone could tell me please the best way to locate the joists to screw into?

On the part that has collapsed I can see the lath, is it a matter of poking up with a thin screwdriver to find the joist, but is it likely that if I poke it too vigorously this will down too?

On the part that is still intact, if it remains intact, what would be the best way to find the joist here. I considered drilling down from the loft either side of the joist so I can mark its position on the wall, but there is chipboard flooring in the loft plus a load of junk and if possible I'd rather not have to take this up and move the junk!


Thank you for any help, this website and the contributors really are invaulable.

Amanda

Moderator

Moved as originally posted in WRONG FORUM (general diy)

 

[masona]

See this on the bottom page.

I prefer to take down the old ceiling down and I know it's very dusty !! You can see all the ceiling joists better this way and you won't hit any electricial wire & pipe as well. Most people do plasterboard over old ceiling and it's not easy in my view.

 

[DAZB]

Work out the centres between the joists by viewing it from the loft ( could be between 400mm and 600mm from centre to centre ) then you can find the first joist from below by safely assume that there is a joist alongside the external wall of the room and then measure in the correct width to each joist centre on the ceiling below. If you do have to prod around to find the first joist then just hold up the vaccuum hose as you do it and all the dust will be sucked up. Once you have found the joists mark the wall on each centre and do the same on the opposing wall and work from these marks .

 

[-dj-]

this is part of a thread that myself and "legs akimbo" commented on a while back....

Posts: 581
Registered: May 1, 2004
Re: Another Plasterboard question!
Posted: Aug 18, 2004 3:55 AM Reply


if you want to avoid the mess leave it up.
punch a hole with a large nail through the ceiling to find a joist. once found punch till you find either side of the joist usually a 2inch joist. mark ON THE WALL either side of the joist you then know where to put your screws. off your first one, mark the rest of your joists, they should be 16inch centres.
you should use drywall screws, but size will depend on thickness of lath and plaster probably 50 or 60mm screws.
having said all that, it would probably be a better job if you pulled it all down..

12.5 boards and not 9.5 because they sag, if it's kitchen or bathroom use foil-backed board.

if you do strip it why not put some insulation up?
kingspan maybe.
good luck.

dj.

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Robbo

Posts: 217
Registered: Mar 13, 2004
Re: Another Plasterboard question!
Posted: Aug 18, 2004 11:27 PM Reply


dj is pretty much spot on. leave the ceiling up its a piece of p**s to over board.
The only thing I would add to dj's advice is start from the edge where the first joist will be and just knock a hole through with your claw hammer enough to feel the joists with your fingers. Find the centre of the joists either side of the room and mark on wall and ping a chalk line across the board when it is up from mark on either side of wall which will be the dead centres of your joist runs evey 14 or 16 inches you will find the next joist, it matters not how big a hole you smack through the laths because they will be over boarded, allways use drywall screws and never nails..... the only earthly reason for bringing down a lath ceiling is if it is sagging and in very poor condition, even minor bumps will be corrected using 12.5mm boards... good sound insulation too.
dj, have you seen the estwing lath hammers, great for overboarding and the head is ideal for slabbing of any type new or old work.


.............................

Robbo

Posts: 217
Registered: Mar 13, 2004
Re: Another Plasterboard question!
Posted: Aug 18, 2004 11:33 PM Reply


Just to add that you must break through the lath with your hammer on every joist to find the dead centres you can not rely on them being at regulation 400mm centres and I repeat dont worry about the holes they will be covered and never seen again.

 

[masona]

I often wondered this, what you lads think of the extra weight with plasterboards on old ceiling plaster lath with 4"x2" joists ?

 

[oilman]

I've been reading the archive posts about plasterboarding over old lath and plaster ceilings versus pulling them down and then plaster boarding.

What about a third way? If you don't have to replace the whole ceiling, how about repairing the hole? go to http://www.periodproperty.co.uk/uncle022002b.shtml#uncle022002-17 and look at the last item on the page for starters. (Don't forget to put some hair in it)

 

[masterbuilder]

when looking for joists, first establish which way they are running by looking at the floorboards upstairs, just bang a nail in the corner of ceiling till you find it then measure along 16 inches or 400mm and bang in nails til u find next 1 etc.
leave nails in till you've done this on both sides, then string chalk line inbetween nails and ping, leaving line and position of joists
be careful of cables and pipes though

 

[amandaeb]

Thank you for your replies.

Mason- thats a really useful article thank you

Daz, thats useful to know- that there is a joist next to the external wall, as you say I can work from there measuring out.

DJ thank you for the tips, and recommendations for screws and plasterboard. I haven't come across dry wall screws but I'm sure I can find out about them.

Oilman, Thank you for your suggestion, I would consider repair but I think it may have gone too far. All the ceilings in the house are a bit bulgy, and I can see, now that some of the paper has come off the ceiling, that there are bulges and cracks. I suspect big chunks will come down if tapped as it sounds hollow. But this may be a possibility in another room.

Master builder thank you for your tips. I am concerned about pipes and cables, I read that cable detectors will find them, but I don't know if I should rely on one, especially as the plaster is several inches thick.

Once again thank you guys, I'll order a hard hat over the weekend and get lots of spare vacuum cleaner bags!

Amanda