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Ceiling Plaster Collapse/de-bonding reasons and Repair guidelines needed

 
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r_srini
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PostPosted: Tue Jun 08, 2021 6:04 pm    Post subject: Ceiling Plaster Collapse/de-bonding reasons and Repair guidelines needed Reply with quote

We are facing a serious problem of large area of Ceiling Plaster in bedroom falling during lockdown. Request for your Expert opinions on reasons why and  suggestions to fix the issue. Below is google photos link, including a video of the damaged area.

View Photos of Plaster Cracks in Ceiling on this Link


https://photos.app.goo.gl/WHrCSzA4CeuVJGtD9


Building is 2yrs Old - Stilt + 3 floors with Lift/Staircase. Back portion of building is Duplex Type with 3rd floors. Front portion of building has 2 floors and open terrace. Building built with Frames - Columns & Beams, Red Bricks, M-Sand (coarse for the most part), stone chips, clear Bore Water (having yellow iron sediments). Footing mostly 'Isolated' and Sloped, 6 feet depth in East side, Eccentric 6 feet depth in West side and middle of South side and North Side. All Roofs have Somany Anti Reflective weather tiles. Plaster in internal walls has chicken mesh near beams/pillars. Soil testing was done before construction. Soil has clay to 10 feet depth and sandy layers below.

Building is NE facing a Main Road and is 16 feet from the Main road at its nearest point. Concrete path is laid between compound walls and building in front and one side. Has 3 Rain Water Harvesting pits of 7 ft depth by 3 ft wide and lined with cement concrete well rounds.


1. Ceiling Plaster has fallen from 2nd floor Bedroom facing East and the Main road. Its thickness is anywhere from 6mm to 20mm. Above this room is open terrace with anti reflective Somany tiles. The North wall of this room has small 1mm cracks on the outer plaster and on the Parapet Wall. During first rains last year the wall was damp in many places as seen in the photos uploaded and water dripped by the wall to the floor. No wetness or plaster cracks noticed on Slab till now.

2. There are small 1-2mm Cracks on other Master bedroom ceiling - like two thin streams.

3. Hollow sound is felt in ceiling plaster in Hall, Kitchen, all bedrooms in many spots on tapping with a thick wooden pole. 2nd floor only. not checked rest of building.

4. We notice slab vibrations with Garbage Truck/Water Tanker movement on Main Road outside. Usually when the trucks crosses pot holes in road and when they are as far as 40 feet away.
After lot of reading SEF forums posts and looking at some Youtube videos, (as a non Civil construction person I feel) - for flat ceiling plaster issue, which is a Damocles sword waiting to fall, rest of ceiling plaster in all rooms must be removed with chisel and hammer and possibly refinish the RCC slab having hacking marks with Putty Coating or Primer coat or Gypsum plaster thin layer whatever is suitable that may not fall later. Wooden wardrobe lofts will be a problem as they are fixed to walls and ceiling.
For Outer Wall Waterproofing may be necessary along with parapet wall. Cracks coated with Dr Fixit URP or PIDIFIN with brush and then filled with Dr Fixit Crack X. Finally Dr Fixit Raincoat Base Coat and Top Coat.  Dr Fixit as promo videos easily available and free site visit available.Thanks,SriniCRACKS Info collected from expert posts here:
Non structural cracking in RCC could be due to - shrinkage, creep, plastic settlement, corrosion, lose of bond etc. Cracking in brittle material and ductile material differs to a great extent. Thermal temperature differences in RCC vs plaster...


The cracks in plaster appear at :-


1) Junctions of old and new plasters
2) Juctions of two diff surfaces (say RCC - Brick)
3) Use of coarse material
4) Use of two fine (silty) sand  -  leads to very fine mesh of cracks called 'crazing'
5) Lesser use of cementations material
6) Excessive use of cementatious material
7) Lack of curing for plaster


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vikram.jeet
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PostPosted: Thu Jun 10, 2021 12:45 pm    Post subject: Reply with quote

Collapse of ceiling plaster

Generally such problem is seen in very old constuction s , some +30yrs. Even there in such buildings , the outside plaster, and not the ceiling plaster ,trouble.
Cannot forsee a building two yrs old troubling
Possible reasons could be:
Curing  after plastering - NIL, That is not done .
Water used not suitable and had chemicals .
Vibration/hammering at upper floor

Vibrations from road traffic , generally do not trouble, if near Rly line some vibrations of passing train if cut off trench not provided

Structure so young must be in defect liability period .
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rajagopalan_hariharan
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PostPosted: Thu Jun 10, 2021 3:30 pm    Post subject: Ceiling Plaster Collapse/de-bonding reasons and Repair guidelines needed Reply with quote

The reasons are any of the following.1) The roof slab surface was not chipped properly.
2) The ratio of morter for plastering is poor quality.
3) The thickness of plastering is high.(Normally 10mm will be adopted)

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pvgraju
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PostPosted: Fri Jun 11, 2021 3:57 am    Post subject: Ceiling Plaster Collapse/de-bonding reasons and Repair guidelines needed Reply with quote

Dear sir,

The following may also be a reason.

1. Sand content may be high in plastering mixture.
2. May be due to high temperature directly effecting plastering due to loss of paint on the ceiling.
3. Ingress of moisture in the ceiling.

Regards,

P.V.Gavarraju
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r_srini
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PostPosted: Fri Jun 11, 2021 9:59 am    Post subject: Re: Ceiling Plaster Collapse/de-bonding reasons and Repair guidelines Reply with quote

Respected Vikram.Jeet Sir,  

I acknowledge all the reasons you listed are possible. There was a vibration in the 1st floor flat below us - i.e. drilling hole in the wall for Air Conditioning outer unit pipe on the diagonally opposite back South West Master Bedroom. The noise was very loud then, as if drilling was right below the affected front room.

Respected Rajagopalan Sir,
I acknowledge all 3 of your reasons listed as possible. This is our fear as well.

Respected PVGRaju Sir,
I acknowledge first and last points as possible. High temperature in roof is also possible as it was summer. But terrace has antireflective tiles,  and there was no loss of paint on ceiling before the plaster fell. Actually there was no ceiling defect visible to eyes from inside the affected room to a lay person.

"Ingress of moisture on ceiling".  - Is there any Easy method to check for slab moisture, as visually we don't see any damp marks on ceiling.

Also Respected SEFIians, could you let me know how to get the issue TESTED to find root cause of the issue? Are there ways to test the plaster that has fallen for quality issues? To check if less cement material used or sand quality is poor etc.?  Are Non Destructive testing using Tools common nowadays?  Any Structural Audit consultants in Chennai you could refer?

Thanks & Regards
Srini
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vikram.jeet
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PostPosted: Sat Jun 12, 2021 4:12 am    Post subject: Reply with quote

Dear sir,

So long as cracks are not there in structure slabs/beams or in walls , there is not any big problem. The plaster needs to be redone . If Builder of yr building agrees and visit to see the the deteriorating plaster, exact reason could be ascertained.
Ingress of water , if there, can be easily visible from underside (ceiling). If there is open roof above, then it is to be seen that during rains water do not stagnate i.e. roof slope is ok .  Also if water tanks are there, overflow water path needs to be checked.

Also please see that after removing plaster, RCC slab underside is not disintegrated , which happens in very old works due to corroding Reinforcement splitting the cover concrete.

Hope your problem be solved soonest.
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es_jayakumar
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PostPosted: Sat Jun 12, 2021 7:21 am    Post subject: Reply with quote

If re-plastering is done, it is advisable to use polymer (SBR) modified cement mortar, for better adhesion to the old concrete soffit /  ceiling.

E S Jayakumar
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