Does Venetian plaster crack?

The answer is yes, it can. Venetian polished plaster is a stronger alternative to other types of plaster finishes but Just like any other plaster it can crack but it is important to understand why. This article "Does Venetian Plaster Crack?" will explain the different types of cracks and the potential reasons they would appear, what measures can be taken to prevent cracks from appearing and what action to take if you Venetian polished plaster surface has cracked.

The most common reason that will cause Venetian plaster to crack is movement in the substrate. i.e the background that the polished plaster has been applied to is moving or has shifted slightly then settled. There are other reasons that will cause cracks such as if the plaster has dried out too quickly or the correct mixing procedures have not been followed however these reasons are uncommon.

Reasons for movement in the substrate:

• Poorly constructed or finished substrates: i.e a stud wall which has been clad with 1x layer of plasterboard has been set out with 600mm stud centres as opposed to our recommended 300mm centres with 2x layers of plasterboard.

• Old buildings: Old buildings can shift over time causing movement cracks for form in Venetian plaster.

• New buildings: Settlement is the main cause of small hairline cracks appearing where the buildings foundations etc. are subject to 'settling'.

• Stress: A building could encounter addtional stress caused by structural alterations to the building itself, structural works or refurbishment works being carried out to the adjoining building.

• High winds: Tall buildings could be exposed to strong winds causing the building to flex slightly, subsequently causing small amounts of movement to the internals of the building. This could cause cracks in the polished plaster.

Reasons for plaster drying out too quickly:

• Extreme weather: In the U.K this is rare but if extremely high temperatures are present when applying certain types of Venetian plaster it could cause the moisture in the plaster to evaporate too quickly which in tern causes rapid shrinking and 'crazing' cracks could appear.

• Airconditioning: If working on a wall where an a/c unit is blowing hot air onto the wall. It is always best to switch off any airconditioning systems whilst applying a polished plaster finish.

• Areas have not been primed: This is extremely uncommon but if the walls are not primed prior to application of polished plaster, the plaster won't adhere properly and could dry out too quick causing shrinkage cracks/flaking.

There are multiple reasons why cracks can appear and multiple ways to reduce the risk of cracks appearing in Venetian plaster applications but all have to be considered prior to the application of the plaster. Unfortunately there will be instances where elements out of our or the main contractors control will cause the plaster to crack such as high temperatures, high winds etc. but we will focus on what we can control. As mentioned the main cause for cracks to appear is movement in the substrate. 

• Ensure the substrate (walls, ceilings) is contructed to a high standard:

This is the element that we have most control over, if a substrate isnt constructed properly cracks could appear.

We have substrate spec sheets in PDF format for each type of substrate build up, these inluded Plasterboard, Solid plastering & Previously Decorated These documents contain detailed instructions on how to construct and finish each type of substrate prior to the application of Venetian plaster. They also include details of acceptable tolerances and images of unacceptable finishing. If you require a specific substrate spec sheet from Marmo please get in touch.

• Anti-crack Mesh:

Anti-crack fibre mesh can be used to strenghten existing or old substrates where there have been cracks previosuly. The anti-crack mesh system is applied directly to existing walls or ceilings and buried into our basecoats of plaster, effectively tying the whole substrate together in one continous mesh. This will greatly improve the strength of the substrate and reduce the risk of cracks appearing in the future. In most cases it will even stop existing or re appearing cracks from returning in the venetian plaster finish.

• Repairing cracked Venetian plaster is a specialist service. We would never advise to attempt repairing Venetian plaster youself 'DIY repairs' will more than likely outcome in causing more damage and highlighting the crack even more so, which could then lead to the entire wall or affected areas being re applied.

• Always contact a specialist polished plaster contractor to carry out your repairs. Ideally you would contact the original installers as they will have your project on file and should know exactly what finish and colour has been installed. This will result in you having an exact colour match once the repairs have been carried out.

• Each situation is unique as to what is causing the crack(s) to appear. An assessment would need to be carried out by a specialist polished plaster company to ensure that the substrate is stabilised prior to carrying out repairs as if this is not done, the cracks will return.

Does Venetian Plaster crack? Yes, it can but as explained in this article there can be lots of reasons for cracks appearing in venetian plaster. It is important to take the necessary steps whilst constructing new substrates or preparing existing or previously decorated walls to ensure the best possible chance of preventing cracks from appearing.

If cracks have appeared, they can be fixed but this must be carried out by a specialist contractor.