Freshly plastered ceilings have developed many cracks

[akist]

Two rooms were plastered a month ago and the ceilings have cracked in many places and it would seem right over the plasterboard joints. The cracks are hairline but are there. I only noticed them yesterday.

The plasterers said they put tapes over all joints, but I was not there to witness it personally. I have not yet told the plasterers of this.

In terms of construction, all ceilings in the house were made in the exact same way, and it is just those two rooms that have developed those hairline cracks. The plasterers who did this job also did a few other ceilings which so far have not cracked.

What is the correct remedy for this problem?

 

[sparkwright]

If it's a plasterboard join, it's pointless trying to fix it unless it really has been taped.

Would also be worth checking the edges of the boards have been screwed to the joists securely.

Perhaps you could find a discreet area to just scrape a small area of plaster off to check it has been taped.

If it hasn't, then you would be justified in getting them back.

(I'm sure it has been taped, it would take a lousy plasterer not to do this.)

 

[akist]

I fitted the boards and there are plenty of screws.

All cracks are on the joints and in both directions. I would say roughly 30% of the joints have developed cracks on those two rooms

It is puzzling as there are so many cracks, not just one or two. Why are there no cracks at all other ceilings done a only a few months ago?

I will check to see if there is tape underneath just to make sure. But am not sure what anyone can do, having now read older threads. Just use a special filler and hope the cracks will not reappear?

 

[sparkwright]

If there really isn't any tape, I would be inclined to knife out the cracks, tape, and re-skim the entire the ceiling.

If there is no tape, it will always crack. They always do.

 

[sparkwright]

Send a picture if you can.

There's hairline cracks and there's hairline cracks.

 

[akist]

Here are some photos I took a few days ago. Maybe I will take some more photos tomorrow.

 

[akist]

Same ceilings freshly plastered a month or so ago

 

[sparkwright]

They are quite noticeable, aren't they?

Had wondered if they were very fine cracks, filling may have the answer, but they are so long and wide.

Are you able to remember if the joins where the cracks have appeared are;
1) Parallel to the joist
2) At a right angle to the joist
3) Both?

 

[akist]

Neither

The joists have first been covered with ply. Then we placed the ceiling boards. About 30 screws per ceiling board and 30 screws per ply board. All ceilings in the house, in all rooms but 2, have been done in this way. The kitchen and living are the only two rooms with cracks and they were among the last rooms to be plastered. If there was house movement or similar we should have had cracks on the other 8 rooms. In addition, 5 or 6 of the other rooms had no tape in joints. So much so that I was promised to get cracks due to the lack of tape in joints. The rooms that have cracked, apparently were taped religiously ( I did not witness it and have no photo evidence ).

 

[BlueLoo]

Ceiling boards onto ply?

Bit odd innit?

 

[Deluks]

^ What he said ^
Being different materials with different properties, plasterboard and ply will expand/contract at different rates.

I'd get some wallrock lining paper and go over the lot.

 

[akist]

I have thought about this for a while, why did cracks appear only on those two freshly skimmed ceilings, there are many more ceilings in the house with no cracks. What is the difference between those two ceilings and the rest of the house?

Factors which are the same:

1) ceiling joists - all the same size fitted within 4 days in the whole house and matured and exposed to the same conditions for one year
2) ceiling construction - ply and then plasterboard, same thickness, supplier, and even the same screws across whole house, no loose boards, nothing moves, nothing flexes
3) maturity of materials used in those two rooms - quite mature ply and plasterboard (about 22 boards in total) and some much newer - cracks have appeared equally on "old" and "new" areas regardless
4) foot traffic above - cracks have appeared equally in places with a lot or with no traffic at all. Other ceilings that have no cracks have seen equal or more amounts of traffic and heavy objects moved (dozens boards of ply and plaster, 25kg to 35kg each). Currently we must have over a ton of ply and plasterboards up there, being moved over ceilings that have not cracked.
5) North-south orientation : cracks have appeared equally in both the north and the south facing room

The factors which are different:

6) plastering conditions - first round of plastering ceilings was done in May and June, weather quite warm and dry ( no cracks ). Second batch was done in October, weather wet and cold at nights ( lots of cracks ). House is not heated.

7) tape used on joints: the ceilings that have cracked have tape on their joints. It was something discussed and agreed with the plasterer (he is meticulous and would have done it regardless). The ceilings that have not cracked have no tape in joints. Go figure.

8) Plaster thickness : the two ceilings that have all the cracks have visible (different colour) joints and you can clearly see the plasterboard outlines after the skimming, even now. The ceilings that have not cracked, you could not see the plasterboard outlines at all. Does this imply that the ceilings that have cracked have had much thinner plaster put on?

Tomorrow I will easyfill one or two cracks and let it dry. If it does not crack again then we might be lucky. If the cracks re-appear the solution will be to reskim the ceilings... And they are large ceilings, about 90m2, will cost me, at best, £10/m2...

 

[Wayners]

Anyone walked above? Flex will cause that from the weight.

I would use a tungsten scraper and create a 1-2mm channel to set tape in.
Fill and sand.
A surface tape will show so sink it below the surface.
.

 

[sparkwright]

Are you saying some ceilings didn't have any tape used, and that all of these ceilings have no cracks?

 

[akist]

Are you saying some ceilings didn't have any tape used, and that all of these ceilings have no cracks?

Exactly that. Oh the irony. I have been given 100% chance those ceilings will crack but they have not yet.

I think now, on the ceilings with a million cracks, the plaster is spread too thin, since I can see the outlines of every single board. Being it too thin it then cracked. Other ceilings you cannot see boards at all; probably a thicker coat, or maybe two coats instead of one.