Common plasterwork problems found in historic houses and how to overcome them

Enriched Decorative Plaster

Historic houses are notorious for issues with deteriorating plasterwork – but what steps can you take to identify problems early in order to prevent a situation worsening to the point where more radical repairs may prove to be necessary?

Common plasterwork problems include cracking, sagging ceilings, falling cornicing and plaster moulding degeneration. They are brought about through a range of factors, but the slow deterioration is often speeded up by an historic building’s vulnerability to moisture and general old age.

How bad is my plasterwork?

The best way to ensure the good health of your plasterwork is to bring in an expert. It is an incredibly specific set of skills that can achieve the correct assessment, conservation and restoration of traditional plaster. Always check the credentials of your chosen advisor to ensure they have relevant experience in heritage environments. There are several layers of seriousness when addressing plasterwork issues and we would always advocate calling in a professional if you have any doubt about the extent of the problem.

Decorative plaster issues involving minor cracks can usually be filled and repaired by a decorator, while major cracks need to be investigated fully before pressing ahead with any repair work.

If a cornice is falling, check if it is moulded or run in situ. Cornice mouldings can be re-fixed or replaced relatively easily, whereas run in situ is much more involved.

Any sagging or bulging can be an indication of failure in lath and plaster, lime plaster ceilings.

Why has the problem occurred?

Understanding the cause of common plasterwork problems is essential in deciding on the best remedy.

The most common source of damage to plaster mouldings is moisture. This can be dampness over time or a water episode such as a flood or burst pipe. Old plaster can also be compromised by sustained vibrations or damage caused by DIY or other building work.

If moisture is at fault, find the source then assess repairs before addressing any plasterwork. Water staining can be decorated over but if plaster is compromised then replacement may be necessary.

Moisture will also affect lath and lime plaster, especially supporting timber laths. It may be possible to patch repair some defective areas, which can be cut out and locally restored, but this depends on the circumstances and should be preceded by a historic plasterwork survey.

Key things to consider

There are some key things to consider with decorative plaster mouldings in old houses. Originally, cornice was made using mortar or lime putty in situ, where a mould was run the length of the wall or ceiling to fashion a seamless decoration. A run cornice usually relies on one form of fixing which is the adhesive bond between the cornice and the wall or ceiling. If this bond fails the cornice will fall.

Plaster mouldings are made from fibrous plaster – a mixture of hessian fibres and Plaster of Paris set into a fixed cast, with timber reinforcement added from behind. Fibrous plaster mouldings are fixed using screws and adhesive and require less time, preparation and clearing up than those run in situ. For heritage and listed buildings cornices should usually be replaced like for like.

If the plan is to match existing mouldings, be aware that this can be time consuming and therefore add to your overall costs. It is, however, going to be necessary in many circumstances if the work involves heritage or listed buildings. Matching existing mouldings will mean using existing material to make a mould from which new items can be cast to repair damaged areas.

Paint removal on decorative mouldings should be carried out by a specialist decorator due to the high risk of damage to ornamental enrichments. It is crucial to understand the depth and type of paint before attempting any removal process.

When it comes to painting and decorating, it is best to use soft distemper as this can be removed by washing off and doesn’t clog up the enrichments.

How to fix damaged plasterwork

It is sometimes possible to make good plaster mouldings using a gypsum-based filler. For fibrous plaster mouldings we can replicate and replace a damaged section. However, as mentioned above, this is time consuming and can be expensive. An alternative is to replace with a similar stock moulding from our online shop. We always try to conserve the existing fabric of any building and only if the plaster is unsafe will necessary steps be taken to secure it.

If supporting timbers and framework are decayed, an expert survey to assess the extent of decay and its likely impact should be obtained.

Fibrous plaster cornices are generally easier to put up and come with a wide choice of styles and sizes, while in-situ mouldings suffer less from any runout of ceilings or walls that can sometimes be an issue in very old properties.

Whilst traditionally cornice mouldings were made from fibrous plaster, more recently they have become available in glass fibre reinforced plastic (GRP) and extruded polystyrene, only plaster is truly authentic.

Heavily enriched cornice mouldings can be more time consuming to replicate when match-existing is required, and this also makes the balancing of cornice, matching the enrichment pattern around a full room, more challenging to complete.

What to do next

Seeking guidance from an expert is especially important in the case of listed buildings. Any changes may require Listed Building Consent from your local authority or conservation officer.

We can provide replacement decorative mouldings to match the existing, however there are other factors that will make each case unique, such as the size of the room, the nature of the damage and whether the building is listed – all situations that we are well used to dealing with at Artisan Plastercraft.


If you are in need of fine architectural decorative mouldings in order to restore the plasterwork of your property, contact our team today. We will be glad to speak with you about the common plasterwork problems we have come across. We will also be happy to offer you a quote for the remedial work required.



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We understand that choosing the right company for your project is important for project success, budget efficiency and your reputation.  We manufacture and install superior custom plaster mouldings, we re-create period plaster features as well as offering traditional lime plastering & lath and plaster.