# Forum Home Renovation Plastering  Ceiling cracks and sagging cornices

## Jacqui01

Hi There, 
I'm relatively new to this all and have just bought a house under contract. The house is late 80's, original everything with no ventilation in ceiling cavity.
The ceiling is cracked badly in the middle of the house and through the open plan areas with sagging cornices (made obvious where it has been attempted to be pinned up).
I have budgeted into price the expense of battening and re sheeting ceiling, however this statement in the builders report has me really worried "*The bracket that connects the roof truss to the wall frame requires adjustment or relocation to allow for independent truss movement under roof load. Door frame movement, sagging cornices and plaster board stress cracks are noticeable. Recommend seeking further advice from a licenced & practicing carpenter."* 
I will get someone out to look at it this week, but what does this mean, and what is the expense approximately?, Have I bought a lemon?
Thanks in advance!

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## phild01

It might be that this assessment was made without an in-roof inspection.  Suggest a builder accesses the roof space and reports as to whether the trusses are good and can drop as normal.
Trusses need to have some ability to drop when loaded with roofing and ceiling sheets.  The internal walls have a bracket that allows for this movement but the deflection should not result in the amount of damage you describe.  Best to have someone determine the cause.

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## Jasey

I think the inspection report is suggesting truss uplift.  If you secure your non load bearing internal walls to the truss securely there is a real possiblilty that seasonal truss movement will pull the walls up and down causing cracking, particular if the ceiling sheets are secured close to the top plate.  If it is truss uplift then you need to ensure the correct brackets are used to allow the truss to move.  But be aware foundational movement could be the cause also.  Fixing the ceiling is not difficult but you need to find the cause first.

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## Jacqui01

Thanks so much, he did get into the roof space to determine this and he also wasn't concerned with foundational movement. Is it possible that with the correct brackets and ceiling ventilation could allow enough truss movement?

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## Rod Dyson

Another consideration is simply that the plasterboard was not installed properly and fibreglass tape or cotton tape was used which is guaranteed to crack over time. 
Cotton tape used in the 80s tends to rot in the joint and loses all strength.  Fibreglass tape was just coming into the market in the 80s and was used for ceiling joints before we realized the cracking problems.   
It is most likely you will fix the problem by re-sheeting. 
There are also a number or reasons for the cornice to be sagging other than issues with the trusses, again due to poor installation.   
I have inspected many jobs in Melbourne where the cornices have "sagged" through the middle of the house.  The cause was uplifting around the perimeter of the slab after rain on clay soil, the centre of the slab does not rise but the trusses do rise as they are fixed to the outside walls and "float" in the centre.  Typically the cornice will let go unevenly causing it to have the appearance of sagging in places.  This was mainly after the drought.  But could happen any where.

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## mudbrick

So Rod are you saying paper tape is the best ?  ( slightly off topic but hey)

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## Rod Dyson

> So Rod are you saying paper tape is the best ?  ( slightly off topic but hey)

  yes

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## mudbrick

Got it! Will stick with paper

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## Littleeml

We seem to be having the exact problem you describe at the moment. The cornices through the middle of the house have 'sagging' in places. Our home sits on clay soil, the front and one side of the house have concrete to it, the back and other side have crushed rock or stones. We were thinking of doing an overlay cornice, but not sure if we will continue to have the same issue. What would be your recommendation on fixing this issue?

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## Cats

Our house is an 8 year old single storey built on clay-based soil in North Melbourne.
We have an issue where the cornice has sagged and cracked evenly at points connected to the roof trusses along the centre internal wall. 
Our suspicion is that the exterior walls have settled over time, moving the truss downwards towards the top plate of the centre internal wall.
We're assuming there was always a gap between the trusses and the wall top plate, and that this gap has reduced as the exterior walls settled.
Every second truss is connected to the top plate via an L slide connector. 
The cornice is attached to the wall board, which does not move, and the ceiling board, which has moved downwards.
Where there is no truss, the cornice is holding the ceiling at its original position.
As the greatest downwards pressure is where the truss connects to the ceiling board, this is where the damage to the cornice is occurring. 
Our proposed solution is to remove the old cornice, allow the ceiling board to drop and then install a new cornice. 
We are doing nothing to the truss or top plate.
----
Any thoughts, comments, or advice?

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## Rod Dyson

> Our house is an 8 year old single storey built on clay-based soil in North Melbourne.
> We have an issue where the cornice has sagged and cracked evenly at points connected to the roof trusses along the centre internal wall. 
> Our suspicion is that the exterior walls have settled over time, moving the truss downwards towards the top plate of the centre internal wall.
> We're assuming there was always a gap between the trusses and the wall top plate, and that this gap has reduced as the exterior walls settled.
> Every second truss is connected to the top plate via an L slide connector. 
> The cornice is attached to the wall board, which does not move, and the ceiling board, which has moved downwards.
> Where there is no truss, the cornice is holding the ceiling at its original position.
> As the greatest downwards pressure is where the truss connects to the ceiling board, this is where the damage to the cornice is occurring. 
> Our proposed solution is to remove the old cornice, allow the ceiling board to drop and then install a new cornice. 
> ...

  This should have been another thread, maybe the mods could shift it. 
This problem can go both ways. the trusses pushing down and cracking the cornice or lifting.   I cant say for sure what the cause here is or if the fix will last.   
Depending on how bad the damage is replacing the cornice is an option.  Hard to really advise properly without assessing the damage. 
Just for the record, when the drought broke many homes in the west had the opposite of this problem where the clay around the perimeter of the house swelled with moisture lifting the slab only around the edges causing the trusses to lift, thereby cracking the cornice line.  I am not sure if the opposite would happen when the ground dries out around the perimeter. 
Post some pics.

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## Cats

Hi Rod thanks for your reply 
Here are some photos of progress so far. the first 5 as it was. The rest of the wall also has the wave but to a much more limited extent. I then removed some of the cornice at the worst spot to see what was going on. photos 6-9. I then went into the ceiling to see the extent of the problem. Photos 10 -12. Lastly i removed more of the cornice to discover the wave low points were all with trusses above them. remaining photos. Since then i have pulled down that section of Cornice (as it was going to have to come down anyway) and now have a lovely hole in my ceiling....

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## jimfish

> Our house is an 8 year old single storey built on clay-based soil in North Melbourne.
> We have an issue where the cornice has sagged and cracked evenly at points connected to the roof trusses along the centre internal wall. 
> Our suspicion is that the exterior walls have settled over time, moving the truss downwards towards the top plate of the centre internal wall.
> We're assuming there was always a gap between the trusses and the wall top plate, and that this gap has reduced as the exterior walls settled.
> Every second truss is connected to the top plate via an L slide connector. 
> The cornice is attached to the wall board, which does not move, and the ceiling board, which has moved downwards.
> Where there is no truss, the cornice is holding the ceiling at its original position.
> As the greatest downwards pressure is where the truss connects to the ceiling board, this is where the damage to the cornice is occurring. 
> Our proposed solution is to remove the old cornice, allow the ceiling board to drop and then install a new cornice. 
> ...

  Hi Cats , just a thought with the L bracket connector, are the nails at the bottom of the slots or is there still play in them. Some people install these incorrectly with the nails in the middle of the slot instead of the top and once the roof is loaded with tiles they can only go down as far as the bottom of the slot whereas the trusses with no brackets can settle further causing a wave in the ceiling. Did you wedge up the trusses or were they already like that. This is a bad idea as trusses are engineered to only be supported off particular points and adding stress to a non load bearing part can cause failure.

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## Snipper

1)  Those L brackets are as good as useless I reckon.  But this is not the cause of the problem. 
2)  Direct stick to truss bottom chords at 600mm centres doesn't help, no ceiling battens to spread the load a bit more even. You may have been right other than small cracks had the ceiling been battened out with 35mm timber.  16mm metal furring channel, not so much 
3) Maybe the roof wasn't fully loaded  (tiles, air con unit etc) when corniced.  Unlikely.  The trusses are built with a camber up and are designed to settle pretty flat when loaded with the engineered designed for loads. Over the years I'd expect maybe 5mm more settlement after it's initial designed settling, not 10mm + as yours seems to be.  Most of the jobs I've done have an internal wall or 2 used to support the bigger span trusses but the truss sits up 5 or so mm higher than these load bearing internal walls during construction due to the engineered camber so once loaded and settled, prior to ceilings, I'll pack and permanently connect them.    
Whether your  wall is load bearing or not I have no idea.  There may be a sticker reading support here possibly on the truss above that wall depending on age and truss company.  Either way, maybe the external walls may have dropped to enable that much settlement. Or slab heave in the centre of the house?   Those wedges are pretty useless cut from end grain and too steep. If those trusses are now hard on top of that wall then its loadbearing whether designed to be or not. 
The cornice is failing/sinking/popping under the trusses and bowing the plasterboard ceiling directly underneath the trusses but in between them it is being held up as much as possible by the cornices adhesion to the wall. It simply can't cope directly underneath the trusses therefore cracking/popping both cornice and plasterboard.  Once all the cornice is removed,  due to the memory the plasterboard ceiling has gained it will be wavy and lumpy along the cornice line and next to impossible to flatten out other than maybe running noggins on their flat between the truss bottom chords flush with the bottom of trusses from inside the ceiling and then screwing the ceiling up into these nogs.  PITA and may or may not pull the plasterboard back in to shape.  Trial maybe. 
First up i'd grab a laser level and get some levels to see whats happening, which is either; 1) external walls sinking  2) internal heave   3) extreme truss settlement combined with rough building practices   4) truss failure.  Very unlikely but there are probably still a few jobs out there that were built using a certain gang nail with a butterfly shaped punch out.  It was used in the 80's for a bit and was recalled shortly afterwards due to truss connection failure. 
Need to fix the problem before re-doing the cornice otherwise it may continue.  Good luck, I don't envy your position.

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## Cats

> Hi Cats , just a thought with the L bracket connector, are the nails at the bottom of the slots or is there still play in them. Some people install these incorrectly with the nails in the middle of the slot instead of the top and once the roof is loaded with tiles they can only go down as far as the bottom of the slot whereas the trusses with no brackets can settle further causing a wave in the ceiling. Did you wedge up the trusses or were they already like that. This is a bad idea as trusses are engineered to only be supported off particular points and adding stress to a non load bearing part can cause failure.

  Hi Jimfish 
the L bracket nail (on the one i checked) was located towards the bottom of the slide not the top. It wasnt at the very bottom but only had a small space to move down left. As our issue seems to be a falling truss i thought that this would be ok.  
The wedge was my fathers idea (ex builder from another country, where he has never encountered this problem) to lift it back into place, however once i saw that all the trusses were like this i removed it as i felt uncomfortable with what it might do to the truss in the future. I left the photo in there as it showed the gap between the top plate and the truss.

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## Cats

> 1)  Those L brackets are as good as useless I reckon.  But this is not the cause of the problem. 
> 2)  Direct stick to truss bottom chords at 600mm centres doesn't help, no ceiling battens to spread the load a bit more even. You may have been right other than small cracks had the ceiling been battened out with 35mm timber.  16mm metal furring channel, not so much 
> 3) Maybe the roof wasn't fully loaded  (tiles, air con unit etc) when corniced.  Unlikely.  The trusses are built with a camber up and are designed to settle pretty flat when loaded with the engineered designed for loads. Over the years I'd expect maybe 5mm more settlement after it's initial designed settling, not 10mm + as yours seems to be.  Most of the jobs I've done have an internal wall or 2 used to support the bigger span trusses but the truss sits up 5 or so mm higher than these load bearing internal walls during construction due to the engineered camber so once loaded and settled, prior to ceilings, I'll pack and permanently connect them.    
> Whether your  wall is load bearing or not I have no idea.  There may be a sticker reading support here possibly on the truss above that wall depending on age and truss company.  Either way, maybe the external walls may have dropped to enable that much settlement. Or slab heave in the centre of the house?   Those wedges are pretty useless cut from end grain and too steep. If those trusses are now hard on top of that wall then its loadbearing whether designed to be or not. 
> The cornice is failing/sinking/popping under the trusses and bowing the plasterboard ceiling directly underneath the trusses but in between them it is being held up as much as possible by the cornices adhesion to the wall. It simply can't cope directly underneath the trusses therefore cracking/popping both cornice and plasterboard.  Once all the cornice is removed,  due to the memory the plasterboard ceiling has gained it will be wavy and lumpy along the cornice line and next to impossible to flatten out other than maybe running noggins on their flat between the truss bottom chords flush with the bottom of trusses from inside the ceiling and then screwing the ceiling up into these nogs.  PITA and may or may not pull the plasterboard back in to shape.  Trial maybe. 
> First up i'd grab a laser level and get some levels to see whats happening, which is either; 1) external walls sinking  2) internal heave   3) extreme truss settlement combined with rough building practices   4) truss failure.  Very unlikely but there are probably still a few jobs out there that were built using a certain gang nail with a butterfly shaped punch out.  It was used in the 80's for a bit and was recalled shortly afterwards due to truss connection failure. 
> Need to fix the problem before re-doing the cornice otherwise it may continue.  Good luck, I don't envy your position.

  Thanks for your reply snipper.  
It is my belief that the wall in the centre is a load bearing wall, but it just isnt carrying one at the moment. The wall runs pretty much through the centre of the house and for most of the length.  
When i pulled the last of that run of Cornice down, after making so many holes why not, i actually felt the ceiling drop, as i removed the last bit into the corner, so it was defn holding the ceiling above the point it wanted to be at. 
I take on board your idea to run noggins between trusses to give the ceiling something to flatten out against, however im not sure if i should fix them to the trusses or just use them as a free floating member to force the ceiling to flatten, and how the ceiling would deal with the extra weight? 
BTW you were right about the wedge, the first one split on me. I should know better - Actually i do know better, i just didnt think it through at the time, because i was focused on the issue (excuses excuses, I know). However i removed it in the end anyway

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## jimfish

Cats as this is a structural issue I would think it would be covered under warranty. Do you know who the builder was ?

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## Snipper

> Thanks for your reply snipper.  
> It is my belief that the wall in the centre is a load bearing wall, but it just isnt carrying one at the moment. The wall runs pretty much through the centre of the house and for most of the length.  
> When i pulled the last of that run of Cornice down, after making so many holes why not, i actually felt the ceiling drop, as i removed the last bit into the corner, so it was defn holding the ceiling above the point it wanted to be at. 
> I take on board your idea to run noggins between trusses to give the ceiling something to flatten out against, however im not sure if i should fix them to the trusses or just use them as a free floating member to force the ceiling to flatten, and how the ceiling would deal with the extra weight? 
> BTW you were right about the wedge, the first one split on me. I should know better - Actually i do know better, i just didnt think it through at the time, because i was focused on the issue (excuses excuses, I know). However i removed it in the end anyway

  Hi Cats,  If there is enough room to crawl around in the ceiling space I'd definitely try to attach these noggins to the trusses but possibly not vital.  I'd ideally use the framing gun to nail them in relatively quickly but if I didn't have one I'd screw them with 75mm screws.  Alternatively somebody will have to hold in position from the ceiling space and the other screwing up the plasterboard into these noggins from underneath.  Taking care to clean off the dust and lumps of crap of the back of the ceiling where noggins are going regardless of your plan of attack. 
Once the settling problem is fixed and trusses supported adequately, I'd screw up the ceiling plasterboard sheet into trusses and noggins by using a temporary scrap piece of timber as long as possible/practical and 19mm or thereabouts thick.  Use just normal wood screws 50 mm long (minimum) spaced accordingly to individual bad spots..   Screw this scrap up over the face of the plasterboard into noggins/trusses but  set it back 40mm or so and even more depending on new cornice size,  try to have the permanent screws which are explained below back 15-20mm from the edge of the new cornice.   
Get something bigger to replace the old removed cornice to avoid having to patch all the damage and dags from the old cornice removal.  Say if it was 55mm cove/scotia then replace with 75mm or 90mm cornice.   Once the piece of temporary scrap timber is screwed up and hopefully pulled the plasterboard flat I'd then drive in permanent screws in beside this scrap piece through the plaster into noggins/trusses using 30mm plasterboard screws but not quite driven as deep as if they were to be filled/patched.  Basically screwed up until only just over or flush.   I would probably put them 100 mm - 150mm apart, even closer in the bad spots but maybe further in the ok sections.   
Once satisfied that there are enough permanent screws in then remove the temporary piece/pieces of timber, patch any holes/damage that will not be covered with the new cornice and ready for the new stuff which once stuck and cured will ensure the ceiling will forever remain flat. (unless structural issues continue)  In the worst case and this technique doesn't work you'd have to cut the crap plasterboard out 200-300mm from the wall. patch.

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## tflex

Hi cats,
Have you found a solution as we are having the exact same issue and would really love some advice!

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## Cats

Hi Renee, sorry for the delay in reply.  What I did was I ripped the cornice down to see how bad it was all going to be and as soon as i got it all off, the ceiling fell to the height it should have been at.   The cement between Wall and Cornice was holding the ceiling higher than it should have been and causing the fracture. in essence it was cracking the ceiling jib because the cornice was stronger than the jib. Once I got all the old cement off i put a new one on at the height as dictated by the ceiling. Stopped it, painted it and voila - just like new but now no wrinkles, rips tears or cracks.   The thing was that the trusses were moving, the Wall, which was in the centre of the house wasnt. The Trusses were installed on L brackets and were working exactly the way that they were supposed to.Once the cornice was removed the ceiling self adjusted just the way it was meant to. It is possible that in a drought the whole thing may move again, but i wasnt prepared to unfix the ceiling jib and refix to the wall (instead of the trusses) so that it wouldnt ever happen again (Only need to remove the first and maybe second screw in the truss out from the wall if you do this, but then need to replace with Dwangs attached to the top plate and screw into those instead). To big a job and may never be needed. And if im wrong ill end up fixing it again.   Anyway thats what i did and i hope that helps.  
PS the big thing was when i removed the cornice and the ceiling dropped to where it should have been. Once i saw that i realised how out of wack it all was; and if it goes the other way i expect it will pop screws which are easy to fill and fix. As this time the Trusses will lift and the cornice will hold the jib down. I suspect (aint no expert) that the amount of pressure induced by the cement on the much wider join far exceeds the amount of pressure that the screw with its little surface area can exert. And just like when you over tighten a screw it will just punch through. 
again sorry for the delay hope this helps

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