Wiki: Lath & plaster ceiling

Made a start...
NT
[[image:IMAG1842-2 Lath ceiling.jpg|right|250px|Laths before plastering]]
'''Lath & plaster''' walls & ceilings are often found in old houses. They c onsist of 2 parts: # Laths, thin [[wood]] strips [[nail]]ed to the joists or uprights, with ga ps between them # [[Plaster]], pressed on so it squeezes through the gaps and grips the lat hs
Historic L&P ceilings use wood laths & lime plaster. Modern L&P is seen occ asionally, typically with galvanised metal EML and gypsum plaster.
==Properties=Old L&P ceilings contain much more plaster than plasterboard, giving much b etter [[noise]] blocking. The thicker plaster also improves [[fire]] resist ance some.
Historic L&P is often in poor condition. If a lump drops down it can cause cuts requiring hospital cleanup and [[Adhesive|gluing]] or stitching.
==Repair=Where its wished to retain an L&P ceiling that's beginning to break, [[scre ws]] & penny washers can be placed into joists to hold pieces up. Don't att empt to screw into lath, its a futile exercise. Pouring diluted [[PVA]] or fresh plaster onto the topside of the ceiling is done sometimes to stabilis e old ceilings. Missing patches are fairly straightforward to [[Fill|patch] ] with plaster. Once stabilised, a damaged ceiling can be skimmed, or in so me cases patch filled.
==Removal=When L&P begins to collapse its usually removed. Though simple to do (whack it), the normal result is filth so severe that it ruins the finish on ever ything it touches. Once gone, either the numerous nails are removed & new p lasterboard is applied, or loose laths are refixed and the whole wet plaste red.
Replacing L&P with plasterboard significantly increases sound transmission from room to room.
==Overboarding=Putting plasterboard over (or technically under) old L&P is another repair option. The sound retaining property of L&P is retained, and the filth from hell is avoided. But locating joists for the new screws can be rather hit & miss. If you can lift a few floorboards above, drilling some tiny marker holes next to joists can be a real help; joist positions can then be pencil led onto the ceiling or the top of the [[wall]]s.
==See also=
[[Category:Basics]] [[Category:Noise]] [[Category:Period Property]] [[Category:Plastering]] [[Category:Repair]] [[Category:Walls]]
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Cool.
Comments inline:
On 01/10/14 07:28, snipped-for-privacy@care2.com wrote:

You forgot the goats hair (or similar) that was added to the mix to give it structural strength.
[Aside: and to think how much they make of adding "microfibres" these days, as if it's something new].
Actually if doing a traditional repair, microfibres might make a suitable replacement for the animal hair.

Cut that - unsubstantiated IMHO

Not untrue but no different to any other old ceiling...

A neodymium magnet is a good way to locate the iron nails and thus the joists - it works on PB ceilings so should work here. Needs to be powerful as the plaster is thick
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snipped-for-privacy@care2.com writes

Excellent. Whilst I have L&P ceilings (and walls) here, I don't have enough practical experience to offer a useful critique, but it certainly seems to make sense.
--
Graeme

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ISTR horse was more common but it could indeed be goat - or ox or cow or any other hair from hairy animals at hand (and failing that sometimes hemp). (I once worked in a Grade I building being renovated where English Heritage insisted on identifying the hair used and importing the best possible untreated hair. Motto seemed to be "no expense is to be spared" [it's not our money]. But at least it wasn't like the polished white plaster in a posh place where they'd insisted on matching the original white hair from kid goats!)
And while AIUI they didn't use asbestos there's also the risk of anthrax :))
If you think I jest http://www.english-heritage.org.uk/publications/anthrax-and-historic-plaster/
--
Robin
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On Wednesday, October 1, 2014 7:28:12 AM UTC+1, snipped-for-privacy@care2.com wrote:

thanks for the feedback. Here's the latest version...
NT
[[image:IMAG1842-2 Lath ceiling.jpg|right|250px|Laths before plastering]]
'''Lath & plaster''' [[wall]]s & ceilings are often found in [[Period Prope rty|old houses]]. They consist of 2 parts: # Laths, thin [[wood]] strips [[nail]]ed to the joists or uprights, with ga ps between them # [[Plaster]], pressed on so it squeezes through the gaps and grips the lat hs
Sometimes animal hair reinforces the plaster.
Historic L&P ceilings use wood laths & lime plaster. Modern L&P is seen occ asionally, typically with galvanised [[EML]] and gypsum plaster.
[[Tools|Lathes]] are never incorporated into ceilings, they're far too heav y!
==Properties=Old L&P ceilings contain much more plaster than plasterboard, giving much b etter [[noise]] blocking. The thicker plaster also improves [[fire]] resist ance some.
[[History|Historic]] L&P is sometimes in poor condition. Falling lumps some times exceed 10kg and contain [[Sand|grit]].
==Repair=Where its wished to retain an L&P ceiling that's beginning to break, [[scre ws]] & penny washers can be placed into joists to hold pieces up. Don't att empt to screw into lath, its a futile exercise. Pouring diluted [[PVA]] or fresh plaster onto the topside of the ceiling is done sometimes to stabilis e old ceilings. Missing patches are fairly straightforward to [[Fill|patch] ] with plaster. Once stabilised, a damaged ceiling can be plaster skimmed, or in some cases patch filled.
==Removal=When L&P begins to collapse its usually removed. Though simple to do ([[Ham mer|whack it]]), the normal result is [[Cleaning|filth]] so severe that it ruins the finish on everything it touches. Once gone, either the numerous [ [nails]] are removed & new [[plasterboard]] is applied, or loose laths are refixed, broken laths replaced and the whole wet [[plaster]]ed.
Replacing L&P with plasterboard significantly increases [[Noise|noise trans mission]] from room to room.
A theoretical risk of anthrax from some old L&P has been proposed, but ther e have been zero cases contracted from working on L&P in the last century.
==Overboarding=Putting plasterboard over (or technically under) old L&P is another [[repai r]] option. The sound retaining property of L&P is retained, and the [[Clea ning|filth from hell]] is avoided. But locating joists for the new [[screws ]] isn't as simple. Options include: *If you can lift a few floorboards above, drilling some tiny marker holes n ext to joists can be a real help; joist positions can then be pencilled ont o the ceiling or the top of the [[wall]]s. *A very strong neodymium magnet can detect the [[nails]] in the joists.
==Materials=Galvanised steel [[EML]] is far faster to fit than wood strips, so tends to be chosen for new work. Where the same construction is required, oak and h azel are common lath materials. Bamboo is occasionally used for laths, its supply in roll form for fencing makes fitting it relatively quick.
For a small minority of [[Period Property|listed buildings]], it has been r equired to use the same type of animal hair as the original L&P.
Hair should be [[Cleaning|cleaned]] (degreased) & beaten.
==See also=
[[Category:Basics]] [[Category:Noise]] [[Category:Period Property]] [[Category:Plastering]] [[Category:Repair]] [[Category:Walls]]
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On 01/10/2014 17:24, snipped-for-privacy@care2.com wrote:

What's EML? (there's a red link, create this page, in the Wiki)
Andy
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On Tuesday, October 7, 2014 9:23:10 PM UTC+1, Vir Campestris wrote:

Fixed. Expanded metal lath
NT
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snipped-for-privacy@care2.com writes

May I suggest a rewrite of that sentence? Reads as though L&P ceilings contain both plaster and plasterboard, but more of the former.
Old L&P ceilings contain much more plaster than plasterboard ceilings, giving >much better [[noise]] blocking.
--
Graeme

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On Wednesday, October 1, 2014 8:40:50 PM UTC+1, News wrote:

thanks, sorted
NT
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No, entirely true. I know someone who caught it. Nearly died. Anthrax is a sporing organism that can survive for hundreds of years as a spore.
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Made a start...
NT
[[image:IMAG1842-2 Lath ceiling.jpg|right|250px|Laths before plastering]]
'''Lath & plaster''' walls & ceilings are often found in old houses. They consist of 2 parts: # Laths, thin [[wood]] strips [[nail]]ed to the joists or uprights, with gaps between them # [[Plaster]], pressed on so it squeezes through the gaps and grips the laths
Historic L&P ceilings use wood laths & lime plaster. Modern L&P is seen occasionally, typically with galvanised metal EML and gypsum plaster.
==Properties=Old L&P ceilings contain much more plaster than plasterboard, giving much better [[noise]] blocking. The thicker plaster also improves [[fire]] resistance some.
Historic L&P is often in poor condition. If a lump drops down it can cause cuts requiring hospital cleanup and [[Adhesive|gluing]] or stitching.
==Repair=Where its wished to retain an L&P ceiling that's beginning to break, [[screws]] & penny washers can be placed into joists to hold pieces up. Don't attempt to screw into lath, its a futile exercise. Pouring diluted [[PVA]] or fresh plaster onto the topside of the ceiling is done sometimes to stabilise old ceilings. Missing patches are fairly straightforward to [[Fill|patch]] with plaster. Once stabilised, a damaged ceiling can be skimmed, or in some cases patch filled.
==Removal=When L&P begins to collapse its usually removed. Though simple to do (whack it), the normal result is filth so severe that it ruins the finish on everything it touches. Once gone, either the numerous nails are removed & new plasterboard is applied, or loose laths are refixed and the whole wet plastered.
Replacing L&P with plasterboard significantly increases sound transmission from room to room.
==Overboarding=Putting plasterboard over (or technically under) old L&P is another repair option. The sound retaining property of L&P is retained, and the filth from hell is avoided. But locating joists for the new screws can be rather hit & miss. If you can lift a few floorboards above, drilling some tiny marker holes next to joists can be a real help; joist positions can then be pencilled onto the ceiling or the top of the [[wall]]s.
==See also=
[[Category:Basics]] [[Category:Noise]] [[Category:Period Property]] [[Category:Plastering]] [[Category:Repair]] [[Category:Walls]]
The easiest way to dismantle a lathe & plaster ceiling is to stamp on it from above. You need some thing/body to hold on to. You can clear an entire room in five or ten minutes.
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On Thursday, 2 October 2014 06:37:23 UTC+1, harry wrote:

Or half a room in 30 seconds if your grip slips.
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Apologies for not dealing with Google Groups carp (sic) formatting. I usually remember...
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