Outside plaster making hollow sound?

There is cracks and a hollow sound in 5 places on my newly plastered outside wall. What could the problem be?

Advice from 12 local tradespeople

old plaster or there was water and this water when it evaporated left air between the wall and the plaster. it just needs to be torn down as much as possible and inspected again and plastered

If crack and hollow sound like it blown
When had scratch coat applied did it allow 7 day in to cure before top coat ??

Hi , this sounds like the render has de-bonded from the wall, allowing the air to get underneath. Which makes the hollow sound, i would have these areas re done to prevent them from completely falling down.

It sounds like your render has blown, the more the moisture gets into the cracks the worse it will get, especially if it rains then freezes

Sounds like he's chopped it back but not prepped the wall properly to control the suction. The wall has then sucked out the water from the undercoat plaster which is now not adhering to the wall.
Hope that helps

First off it should be render or k rend & not plaster outside... Also if it sounds Hollow, It sounds to me like it has blown, which needs to be hacked off and re-done.

Could be the cause of many things first I have to see to tell what it's all about (could be air pocket ,dust creating air pocket,could be an area with no good pva application I have to see etc..

sonds like it has come away from the wall not bonded properly

The old walls may have been painted with an oil based paint which will repel the plaster

If the render is on brick/block then it shouldn’t have any hollow sounds when tapped… the cracks will allow the water to get in and eventually just gets more defected over time… I would call the plasterer back to give his take on it but if it’s cracked an hollow then it sounds like it will have to come off and be re-done unfortunately

The plaster has not bounded to the surface most common reason is when a plasterer has not p. V. A glued the surface properly or its just dryed too fast cos the suction of the background has not been dealt with. (blown plaster)

probably the work was done incorrectly, not enough materials were used previously

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