What's the truth about "Saddle Plaster" ceilings?...

[Batpig]

Dear Chaps,

I was talking to a fellow today about a unit that I have bought that needs a fair bit of renovating. When we got on to the subject of ceiling repairs and I told him about the usual little "popped-nail" holes, etc. and whether I should try to repair the ceiling before adding some 90mm cornices (there are presently just 1" square-profile sticks for cornices), or whether to pull the existing ceiling down altogether and put in all-new gyprock and cornices (so as to avoid throwing good money after bad), he asked me what year the unit block was built in...

When I replied "In the '70's I think...", he told me a little about a story he had seen on "Today Tonight" just recently that had something to do with ceilings falling down in houses that were built back in the '70's. I went to the "Today Tonight" website when I got home and it turns out that the story had more to do with Insurance companies trying to dodge claims made under Building insurance policies. The example of the ceilings was cited in the story because apparently it is fairly common for this particular type of ceiling (made from something called "Saddle Plaster") to have problems and sometimes even fall down (thus leading to claims...)

The obvious questions are:
Has anyone heard of "Saddle Plaster" before?
Does it indeed have a particularly bad reputation for problems?
Was it used up here in Brisbania back in the '70's?
If so, how would you go about identifying it?

Thanks in advance,
Batpig.

[Bloss]

Not sure what a 'saddle plaster' ceiling is, perhaps your mate is referring to ceilings built before the 70s when gyprock style drywall plaster sheets with paper surfaces and fixed by nails or screws and glue became the norm.

Plaster sheets until then had a smooth plaster surface on the ceiling side and a rough finished surface in the roof and were attached to the ceiling joists using wet plaster & horsehair rope "saddles" over the joists and nailed from underneath too (gal clouts). There were plaster factories in each largish town that produced this sheeting (also reinforced with horsehair or sometimes coir or other natural fibres) so quality of the sheets and fixing varied.

If your house was built in the 70s then the ceiling was probably simply nailed to joists or battens without adhesive.

The type of plaster or ceiling material (it might even be compressed AC, fibro, sheet) is pretty much irrelevant IMHO. So long as you can re-fix and secure the existing ceiling there is no need to remove it at all - the only question is whether the ceiling timbers are solid and as level as you want them to be ie: ceiling joists and/or battens. (Of course if it was compressed sheet then masks and following asbestos safety rules when drilling are mandatory)

If the ceiling levels are OK with no sagging for example, then simply re-screw to the existing battens or joists to tighten the sheets up, then patch the ceiling, fit the new cornices and paint. You might even be able to leave the existing corner blocks in place, but probably they will need to be removed.

If you wanted a 'new' ceiling or if there is significant sagging or out of level, then you could screw new plasterboard directly over the existing ceiling into existing battens or rafters and then cornice, or if the ceiling is badly sagged or out of level (some people will put up with more variance than others) then you can put battens in, levelling to as you go (after having determined levels around the walls beforehand and using blocks, plastic wedges or spacers).

Once the ceiling battens are in place (screwed through the existing ceiling plaster into the roof timbers - battens or joists) sheeting and cornice goes up the same way as in a new ceiling.

[Tools]

(Of course if it was compressed sheet then masks and following asbestos safety rules when drilling are mandatory)

It won't be compressed, but if it is asbestos I would suggest you have more respect for your health and don't touch it.Definitely don't drill in to it! Get it professionally removed.

Tools

[peter_sm]

Personally I would not remove a ceiling plaster unless it was falling down.

I would maybe fix it with a few extra screws, then screw fit new 'Rondo' channels over the top and screw new plaster and fit new cornice over the lot.

http://www.rondo.com.au/rondo/

[Batpig]

Dear Fellas,

Thanks for the replies - especially your's Bloss.
Tools (and Bloss), the sheets are definitely not Asbestos - I got stuck into a cracked join today with a Laminate Trimmer (I'm not kidding ) down (or should that be up) to the underside of the nails over a width of 50mm or so, and the very fine snow that I (and the whole room...) got covered with was white - not grey...

In the interim before your replies came back, I found another thread on the subject which hadn't shown up when I first searched the Forums because it uses the word "Saddles" (as did you Bloss) rather than what I searched for, which was "Saddle". Anyway, here it is:

http://www.woodworkforums.ubeaut.com...ad.php?t=54428

Today's experience has, umm, crystalised my thinking somewhat on the matter. There are a few of those cursed cracked sheet-joins, and the unit has minimum height ceilings (as in 2.4m I guess), meaning that only Oyster Lights and such will look in place. Therefore, bulging repaired joins will stand out like a Shag on a Rock due to the shallow angle of the ceiling lighting... Additionally, the unit is on the top floor underneath a "flat" tin roof (meaning not much roof space above the ceiling), so to avoid worsening the temperature in the place during the upcoming (will be a record hot one...) summer, I'm not keen on dropping the ceilings any further - a'la your suggestion peter_sm. A whole new ceiling, with new cornices at the same time, installed by Pro's, would seem to make a lot of sense.

But after perusing the abovementioned thread, I can see that peter_sm is not alone in expressing a general reluctance to remove ceiling sheeting, except as a last resort. From what I've been able to see of the roof, I wouldn't figure on there being a lot of dust on top of the ceiling sheets. Rather, to my mind, the biggest problems with replacement (by Pro's) would be:
1) The removal of any adhesive (if happened to be used for the old sheeting) from the underside of the ceiling battens before any new sheets could go back up (there is just no way I can get into the roof or lift any part of it to have a look for telltale signs...)
2) Even if there isn't any old adhesive between the battens and the existing sheets, just getting the old nails out of the battens would surely be a challenge...
3) Would any insulation that might be up there want to fall down...

Gentleman, what are your thoughts on these and any other (related...) matters you might care to name...

Many Thanks,
Batpig.

[rod@plasterbrok]

The corect term is scrim and it is done with sizal from the agave cactus. In the war years hessian was used as sizal was unavailable. The term for the sheets is fibrous plaster sheet.

A flat roof may not have been scrimmed just nailed up! Depending on how good the original tradie was.

It is not uncommon provided the ceiling battens themselves are reasonably level, to just screw the sheets directly over the old fibrous plaster sheet. If you do this and as suggested above screw up the existing ceiling to take out the sagging, leave the screws just proud of the surface. Once you break the surface the screw will just pull through. As you are putting another sheet over the top these screws wont be a problem.

I still use glue for what its worth but also screw at 400mm centers eg. a screw in the center and one on each side between the center and the edge.

Did this in the ceilings of a mates house several months ago. Leaving the sheets there adds to the insulation and the sound proofing.

Cheers

[powderpost]

Very early in my apprenticeship, (late 50's), I off sided for a plasterer doing walls and ceilings. The plasterer actually made the sheets to suit the job in hand, by pouring plaster on a large flat table. While this plaster was still fluid, we rolled in sheets of hemp, then the sheet topped off to 1/2". The sheets were fitted by nailing two galvanised clouts about three inches apart and about fifteen inch centres. The clouts were slightly "countersunk" of the hammer, and 'patched' up with plaster. After each sheet was fitted to a ceiling, it was "scrimmed" by fitting a wad of hemp soaked in plaster over the ceiling batten, this "gluing" the sheet to the batten. As far as I am aware, adhesives were used only after the introduction of 'gyprock'.
Jim

[gpkennedy]

I tend to agree with previous posts, don't remove the existing ceiling.
You will create dust and junk and then have to dispose of the lot. Those rondo batterns are easy to install if you use a screw gun rather than nails. Once you have made your decision you need to locate the existing rafters with a stud finder or a few sample drill holes. If you are using a drill consider attaching a clear DVD holder to the end of your drill to catch the dust. It helps if you moisten it slightly to fix the dust to the DVD holder. Mark the rafters off with a mark on the wall, a small dab of bluetack will do the trick.

Next use your chalk line to flick a line showing where the rafters are. IE hold the chalk line from one piece of bluetac to the other and give it a flick.
Use a long straight edge (level) to work out the lowest point of the ceiling. Use your screwgun to fix the slowest sagging sheets back home so it it is reasonably flat.

Next you need to draw a line around the wall at the lowest point (worst sag) of the ceiling. What you basically do is to take the long straight edge and pivot it on the lowest point on the ceiling and mark at each corner. use a chalk line ( one of those string lines you wind out which contain chalk) to join the four corners of the room.

Now you have a level line around the sides of the room. The rondo channels should be fixed to this level (at right angles to the rafters. Pack them where necessary. The plaster sheet glued and screwed to the new rondo batterns.

You will find that your new ceiling will be probably at the bottom level of your existing 1inch existing cornice thing. New cornice can then be attached without removing anything.

Hope that this a clear as mud.l

[peter_sm]

Lowering ceiling should not be a concern. The drop will be about 25-30mm. Not much considering the implications the removal of the other original sheets can have with waste disposal and possibility of insulation dropping down.

I did this system exactly when doing bathroom renovations, and was able to re level the ceiling as the original ceiling bearers were not perfectly level anymore.

Good idea gpkennedy added about not having to remove the cornice either

[Batpig]

Some superb replies Gents, with some truly lateral thinking. Australia kicks R's in this regard...

gpkennedy and peter, as fate would have it, the little cornice pieces must be more like about 30x30mm, because a sample piece of 90mm plaster cornice just wont quite sit over them successfully. Would be great if I could find a little power tool that would take off just a 5 or 10mm bevel from the bottom-outer corner of the timber strips, but it would have to be a fairly narrow tool...

Guys, I'm pretty sure I saw paper when I tried to kill my lungs with the Laminate Trimmer the other day (Maybe it's a case of what Bloss said very early in the thread when he suggested that perhaps nails - but no glue - had been used, hence the problem). So the following question begs...

Now, have I got this straight - I wouldn't be able to secure the existing sheets (without adding new ones underneath) by just putting screws in through the original joins and then just filling over the resulting holes, would I? (or would the screws either pull up on the existing joint-filler without getting down to the paper, or if I drove them deeper, would they not know exactly when to pull up on the paper without going right through it?)

Many Thanks again. If I have any more questions after the above, I think I will start a new thread because there's too much good stuff being said to me here that has more to do with repair than it has to do with "Saddles" of plaster...

Regards,
Batpig.

[gpkennedy]

Hi Batpig
before you start grinding back the cornice, don't forget that the cornice will start lower than existing plaster, ie, allow for new plaster plus rondo channeling.
Cheers
George

[Bloss]

Removing ceilings is mostly just extra time and effort and little to gain over leaving in place as well as being dusty and messy so I try to avoid it if possible.

Just re-screwing the existing sheets might work - and given it is a simple task might be worth a try anyway to see if you get the result you want. Only if the sheets lift to level and are secure would you then patch and fill and put up cornice.

If there has been no jointing tape used then you will find it very hard to ever stop the fine cracks re-appearing although I have had some success by using an acrylic flexible filler (like no more gaps) rather than plaster stopper.

As others have said it is likely to give a better job if you use battens (of steel or timber) level them up as described above then put new sheeting and cornices on.

If the existing corner board is only 30mm then that is roughly where the new ceiling surface should finish - a drop of that amount will barely be noticeable in a 2.4m room and as pointed out above no need to remove them.

[Dirty Doogie]

Hi BP ,

Could you just clarify? You do have fibrous plaster ceilings? Or do you have Gypboard (by Wunderlich) an early form of gyprock? Or is it something totally different?

The 30mm beading instead of cornice alerts me to a few practises that were in vogue then in Brisbane with cheaper builds and I suspect you may not have true fibrous plaster. Also I think they would have just nailled any ceiling up especially as it is a flat roof and early adhesives used to fail regularly in Brisbanes humidity and heat.

And those 30 mm corner beads - dont take them off - they might be holding the edges of your ceiling up.

[Batpig]

Dear Doogie,

Now that some of the Lads have explained the "Saddles of Plaster" concept to me, I don't think it's fibrous plaster either because for starters the plasterers wouldn't have been able to get up into the ceiling to drape the saddles because the roof is very "Flat" and there is probably only about 300mm or so of height from ceiling sheet up to roof sheet. And surely the roof would have gone on first... I think the introduction of plasterboard back in the 70's must have paved the way for the advent of the "Block of Flats" with the said lack of any room to move in the ceiling space because of the extra fixing strength that the plasterers suddenly thought they had with the new paper linings. Trouble is, they may not have realised straight away that "nails alone" were not up to the job, and as has been pointed out to me in this thread, this may well be my problem.

Mind you, as you have suggested, bad glue could be the case too, but I don't actually know yet whether or not glue was even used (hence my other thread up in "Roofing" where we're talking about lifting the Klip-Lok to have a peek...)

As regards whether it is Gypboard or Gyprock, I can't tell yet. Would it say on top if I could look under the roof sheeting? As best as I can tell, the Block was built in either '73 or '74, and "Cheapness" certainly seems to have been one of the main construction criteria... If the problem was Bad Glue, do you think the glue would let go of the Battens, or the Plaster?

Don't rush with any reply, Doogie. Won't even be able to look under the roof until Friday at the earliest...

Many Thanks,
Batpig.

[rod@plasterbrok]

Doubt if it was a glue failure more likely to be nailed only.

Back in the early 70's you would have had either Gyprock or Victorboard Boral bought out Victorboard in or around '75.