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Guide to Plastering an Old House

Plastering an old house can be a daunting task, but it is an important aspect of maintaining the integrity and charm of an older home. Many houses built before 1950 have original plaster walls, which require special attention and care when it comes to repairs and maintenance.

Guide to Plastering an Old House
Guide to Plastering an Old House. Source:

Whether you are looking to repair a small crack or completely replaster a room, this guide will provide you with all the necessary information to get the job done right.

One of the most important factors to consider when plastering an old house is the type of plaster used. Plastering materials have evolved over time, and older homes may have different types of plaster, such as lime plaster, which require different techniques and materials for repairs.

Understanding the type of plaster in your home is crucial to ensure that repairs are done correctly and do not cause further damage to the walls.

It will also cover common issues that may arise during the plastering process, such as cracks and bulges, and provide solutions to fix them.

What kind of plaster does my home have?

  • Homes built before 1919 traditionally used lime plaster as the finishing material, though its usage could have extended until the 1950s when plasterboard and gypsum became more prevalent. For more details, consider exploring our lime plaster guide.
  • A pinkish colour typically signals a plaster that’s bound with gypsum.
  • A slight off-white tint usually means a lime plaster.
  • An earth-toned shade implies the presence of an earth binder.

In the event that your vintage home has been re-plastered using contemporary materials, or if you’re up against damp walls, it could be worthwhile to consider a switch to lime plaster.

Look Out for Historic Markings

When renovating a historic house, it’s important to look out for any historic markings that may be present on the plaster. These markings can provide valuable insight into the history of the house and can even serve as inspiration for the renovation.

It’s important to preserve as much of the original plaster as possible. This may mean carefully removing any damaged areas and patching them with new plaster. It’s also important to use plaster that matches the original as closely as possible in order to maintain the historic integrity of the house.

How Traditional Plaster Is Made

Traditional plaster is a mixture of lime, sand, and water, and sometimes horsehair or other fibers. This plaster mixture is applied to a surface, usually a timber lath, to create a smooth and durable finish. The plaster mixture is typically applied in three coats: the scratch coat, the brown coat, and the finish coat.

The scratch coat is the first and thickest coat of plaster, which is applied to the lath. The purpose of the scratch coat is to create a base for the other coats to adhere to. The scratch coat is rough and uneven, with deep grooves and scratches to help the next coat bond to it.

The brown coat is the second coat of plaster, which is applied over the scratch coat. The brown coat is smoother than the scratch coat but still rough. The brown coat is used to level the surface and provide a base for the final coat.

The finish coat is the final coat of plaster, which is applied over the brown coat. The finish coat is the smoothest and thinnest coat of plaster. It is used to create a smooth, even finish on the surface.

The traditional plastering technique is a time-tested method for creating a durable and beautiful finish on walls and ceilings. The use of timber laths and lime plaster allows the walls to breathe and helps regulate moisture, which is important for the longevity of the plaster.

Gypsum plaster is a modern alternative to traditional lime plaster. Gypsum plaster is made from gypsum powder, which is mixed with water to create a smooth and easy-to-apply plaster. Gypsum plaster is faster and easier to apply than traditional lime plaster, but it is not as durable or breathable.

When is it time to replaster walls and ceilings?

Plastering an old house requires careful planning. Old houses often have plaster walls and ceilings that may need occasional repairs or complete replastering. Knowing when to replaster can be a challenge for homeowners, but it’s important to address any issues before they become more serious and costly to fix.

Plasterwork is designed to last indefinitely, but when deterioration sets in, it can manifest in various ways:

  • Formation of cracks
  • Unstable plaster or separating layers
  • Presence of stains
  • Water damage
  • Crumbling or flaking
  • Mechanical damage and absent areas

Such deterioration often appears more severe than it actually is, and repair is frequently a viable option instead of complete replacement.

Any necessary replacement should ideally consist of the same materials and number of coats as the original. Ensuring sufficient hair or other reinforcement is particularly critical when dealing with flexible substrates.

It’s recommended to avoid using plasterboard if possible. Unlike traditional plaster finishes, plasterboard is flat and can seem incongruous in a period property, particularly with older ceilings.

As a rule, ceilings are relatively straightforward to replaster. When needed, laths can be replaced – best secured with screws to minimize vibrations. Lime plaster is then applied over them, seamlessly blending with the surrounding surface.

How Much Does Plastering Cost?

Plastering an old house can be a complex and expensive process, but it’s worth the investment to restore the beauty and character of an older home. The cost of plastering varies depending on several factors, including the size of the room, the type of plaster used, and whether the work is done by a professional or as a DIY project.

Typically, working with a specialist plasterer who has expertise in handling traditional finishes in period homes tends to be more costly than typical plastering jobs.

For a standard task using gypsum-based finishes, the cost generally ranges from £450-£750 for walls in an average-sized room, and £200-£350 for the ceiling. However, the price can potentially double if lime or unique clay coatings are required.

Plastering an old house with lime

Ensure you hire a lime plasterer with proven expertise. Many plasterers may claim to have this skill, but in reality, not all can deliver. Ask for a reference from a recent project.

Alternatively, engage an on-site trainer to instruct a group of eager plasterers. Your lime supplier should be able to suggest a local trainer.

Take advantage of the technical guidance offered by lime suppliers when purchasing your plaster.

Depending on the level of smoothness you desire in the final outcome, you’ll need to apply two to three coats. The finest quality requires three coats, but generally, two coats are sufficient. If you’re working within a tight budget, consider using a reed mat instead of riven laths for the ceiling – that is, if you decide to plaster it with lime as well.

This alternative can result in substantial savings. Secure it to the bottom of the joists using laths and screws. The mixture for the first coat, or the ‘scratch coat’, should consist of one part lime putty to three parts sharp, well-graded sand, generously mixed with animal hair. This composition is known as ‘haired coarse stuff’.

For a sleek finish, apply a setting coat consisting of one part lime to two parts fine sand, referred to as ‘fine stuff’. This mixture can also be obtained ready mixed. Unless advised differently by your plasterer, purchase your plaster ready mixed by the tonne and have it delivered to your site.

Avoid leaving bags of haired plaster unused for more than four weeks – the hair will begin to decompose due to the lime’s alkalinity.

Plastering an old home with lime can be a messy and time-consuming process, but it is worth it for the beautiful, traditional finish it provides. Get in touch with us if you need help with any types of plastering projects. Our team at Ralph Plastering will be more than happy to help.

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