Top Tips For Repairing A Cornice

Cornices, besides making any room or roof seem beautifully elegant, also has an important practical purpose of covering the joint between the walls and ceiling of a building.

Whilst the cornice dates back millennia to the era of the classical order, as the top part of an exterior entablature, it was first brought indoors as part of Italian renaissance architecture.

Whilst we have seen so many different creative styles and eras of cornices, the common ground between them all is how difficult a design can be to restore. This is in no small part because of how many layers of paint need to be removed to reach the original plaster.

In some small cases, however, it is possible to do some mild repair work yourself. Here are some ways to make the job easier.

Use a Paint Removal Product

Whilst sugar salt, a wire brush and many many hours of labour can remove the old layers of paint, it is far easier to use a specialist paint removal product that can soften the old layers of paint and make them easier to remove without damaging the cornice plaster.

Be very careful when removing paint, as the plaster underneath it is both weaker and older.

Use Multiple Plaster Coats

As anyone who has made a plaster sculpture will know, plaster is a versatile but frail material that is prone to breaking.

Once you have applied your first coat of plaster and waited for the material to dry fully, apply a second coat of plaster, let that dry and use a dedicated plaster paint to protect the whole design from future damage.

Cornice & ceiling rose restoration

I’ve been posed one question often recently which is; do you use a chemical paint remover or steam machine to remove paint from a cornice/ceiling rose. In this post I’ll explain my preferred choice, and a brief summary of the two options.

I use a chemical paint remover; however, I can easily argue for and against in this debate. For one, I’ve never encountered a problem myself using a chemical (although I’ve heard many others have). The chemical I prefer to use must be applied and left for a minimum of 24 hours to take effect which can seem time consuming and costly to the client. Once the chemical has been removed, the distemper and general build-up of dirt must be removed with lots of clean water, various brushes and ‘picking tools’. On average, one would hope to apply and remove 3 metres of paints per day, including the cleaning with water. There must be strong health and safety measures adhered to when carrying out this method as the chemical is extremely potent – I have the scars to prove this! As long as the chemical isn’t left on the plaster for more than the recommend maximum allowance of 72 hours, then there is no reason for the plaster to be damaged. A test patch is always recommended before carrying out any extensive work to determine the suitability of the chemical for the job (there are lots of chemicals available for use).

The steam method is an interesting one which I’ve seen used to good effect. There are two reasons I choose not to use it which are as follows:

1)    I don’t like to pressure water into old plasterwork for obvious reasons. Although you can debate that you may only need to use the same amount as required in the chemical method, I don’t like the fact it is forced in with a pressure gun.

2)    Adding water is one thing, but boiling hot water puts me off even more. Although I haven’t tested this in a lab, my gut instinct tells me that this method brings more risk and therefore more chance of damaging the existing plasterwork.

As previously mentioned, I’ve seen other companies use the steam method correctly with an equally fantastic outcome, and I’m sure that I could find bad attempts on both options. Perhaps I’m just a one trick dinosaur who likes what he knows and knows what he likes!

Deciding whether to restore your original plasterwork or start again

This week I’ve had three separate site meetings, all of whom have received conflicting opinions from building contractors relating to the title of this post. Here I hope to offer some clarification.

When purchasing a house which has original plasterwork, or even if you already own a home with original plasterwork, before beginning a big renovation you will often invite a minimum of two building contractors to propose a scope of works. It isn’t uncommon to have a difference of opinion among the potential workers – often reflected in the price, after all, every construction worker will have their own vision - and with this vision they will have their own method of achieving it.

            So, who do you listen to? You’re probably looking at an original lath & plaster ceiling with original cornicing and ceiling roses to match, listening to someone telling you to rip it down and install a new plasterboard ceiling. DON’T LISTEN! As previously mentioned, three times this week I’ve visited potential clients who have been told the above, all of whom I’ve instructed not to listen. I will say it simply, when deciding what to do regarding specialist plasterwork, GET A PLASTERWORK SPECIALIST TO HELP YOU.

            I can only speak from my personal experience; thus, I would hate to generalise in this post. Too often however, contractors are looking for the simplest, most cost effective method to complete a job. This method is often not the most beneficial to the client. There is no calculation to determine whether a ceiling is safe or unsafe, indeed this is down to the professional opinion of the person you are speaking to. The person you are speaking to, therefore, needs to be someone that can determine whether or not the plasterwork HAS to be removed, or whether it can be restored. Of course, the question after this is decided will be how the cost of restoration compares to the cost of replacing it. This, however, provides more options to the client – which surely is the best outcome, isn’t it?

Plaster Cornices

Here are some points worth noting to aid your decision when contemplating different cornice products, as well as to help eliminate paying for a poorly-made product:

·      Traditional cornices were cast using three materials; Plaster of Paris, hessian and wooden laths.

·      Modern cornices are now made from polystyrene, plasterboard or glass-reinforced plaster (GRP) commonly.

·      Many companies still make cornice traditionally, particularly in England.

·      There are many different quality plasters available for manufacture; varying from approximately £5 per 25kg bag, up to £40+ per 25kg.

·      There are different lath thicknesses. Naturally, you will want to use the thickest lath possible, which will benefit the strength and fixing of the cornice.

·      Traditionally made plaster cornices adhere to most fire regulations rules, if made correctly.

·      Every cornice should have a bracket (lath or hessian) on the back to increase strength.

·      Hessian allows the cornice to be flexible. This is a great advantage when working in a building where the walls and ceilings aren’t straight or level.

·      There should be no hessian visible on the finished face of the cornice once dry.

·      The cornice should be around 7-10mm thick in all places – to avoid weak points.

·      If there is cracking visible on the face of your cornice, it is likely because the laths were dry in the process of manufacturing the cornice.