Lime Plaster Ceiling Explained

Lime plaster is a traditional building material that has been used for centuries. It's made by mixing sand, water, and lime and has been used to create beautiful and durable finishes on walls and ceilings.

In this article, we'll be focusing on lime plaster ceilings and exploring their unique properties, benefits, and challenges.

If you're considering a lime plaster ceiling for your home or project, it's essential to understand the basics of this material and its application.

In this article, we'll introduce lime plaster ceilings, including their history, composition, and advantages. So, let's get started!

What is Lime Plaster?

Lime plaster is a classic form of mortar that is typically used to coat the surface of the walls and ceilings of an interior space before painting. The earliest documentation of its use may be found in northern Jordan, dating back over 140 centuries.

Lime, sand, and water are the primary components that go into its creation; however, other types of fibres, such as animal hair, may be added to the mixture to fortify it and guarantee that it has a strong bond with the substructure.

The lime that is used in the plaster is produced by burning materials such as limestone, chalk, or seashells that are composed of calcium carbonate. This results in the production of quick lime.

Lime may be broken down into two primary categories:

• Pure limestone produces non-hydraulic lime, which may be purchased as lime putty. It possesses remarkable adaptability as well as breathability.
• To create hydraulic lime, limestone is combined with natural impurities that include setting agents. Hydraulic lime is sold in powder form, and as it comes into contact with water, it begins to solidify.

Clay plaster is comparable to Venice plaster in that it is natural, breathable, and highly traditional; however, clay plaster utilises clay rather than lime. Both types of plaster contain lime. Venetian plaster is one sort of plaster.

How Do I Identify Lime Plaster?

If you live in a house that was constructed before 1919, there is a good chance that lime was used to plaster the walls. However, even if your home was constructed after this year, it does not necessarily indicate that lime was not used to plaster the walls.

Plaster made from lime often has a creamy white appearance, contrasting to the reddish hue of plaster made from gypsum-based mixtures.

Check for the presence of sand and hair when attempting to determine the kind of plaster on your walls. Sand and hair are often strong markers of lime plaster, as is the fact that the finish is pliable to the touch and visibly old.

Lime plaster was most likely utilised in constructing your walls if they were constructed using lath and plaster, cob, or solid masonry.

Why Use Lime Plaster?

Lime plaster has numerous benefits, and despite the fact that it has been completely supplanted by newer plasters based on gypsum, more and more people who are renovating older homes and those who own period residences are becoming aware of its significance.

Those who are building new homes are also beginning to see the advantages of using lime plaster.

Why, then, do people use lime plaster?

• It protects against dampness. In contrast to more solid cement or polymer-based renders and plasters, lime plaster is known as a "breathable material," which means that air is able to travel through it. Because of this, moisture that accumulates will be able to escape, which means you won't have to worry about damp problems. The adoption of new materials that are impermeable contributes significantly to the problem of dampness in older buildings.
• It is a choice that is kind to the environment. Lime has the potential to remove carbon dioxide from the air, in addition to taking far less energy to create than the majority of other contemporary varieties of wall covering.
• It has the potential to enhance air quality. Plaster made of lime has a property that makes it somewhat similar to a natural dehumidifier in that it can draw moisture out of the air when it's needed and give it back when the air becomes too dry.
• It will last for a very long time. Lime plaster is capable of penetrating deeply into even the tiniest spaces and making a strong connection because to the extremely fine particles that it is composed of. In addition, because of the formation of calcite crystals over time, lime plaster actually gets stronger with time.
• It may be bent or twisted. Lime is a fairly forgiving substance, and it has a lower likelihood of cracking compared to materials that are more brittle, like cement.
• It is really appealing to the eye. Lime plaster has a wonderful, soft natural feel that is truly quite distinctive; it may be utilised in houses that are either rustic or contemporary.

Is Lime Plaster Expensive?

Plastering your home using lime plaster is often going to be more expensive than plastering your home with cement or gypsum.

This occurs for a few different reasons if you must know. To begin, the procedure of placing lime plaster takes more time and is more complicated, which results in increased labour expenses; nonetheless, the majority of plasterers will still only charge a regular day fee for their services.

The second reason is that the cost of buying lime products is often higher than the cost of buying cement.

The sort of lime plaster that you employ will also have an effect on the ultimate price tag.

Is Lime Plaster Better Than Gypsum Plaster?

Plaster made of gypsum should not be confused with cement plaster. It is manufactured from gypsum (a mineral) that has been partially or totally dried, and it is typically coupled with additional hardeners; it is presently the type of plaster that is used in houses more frequently than any other.

Even though it is commonly considered to be a contemporary building material, gypsum has actually been in use since the 16th century, when it was frequently mixed in with lime.

In point of fact, it is still occasionally added to lime in an effort to speed up setting times, despite the fact that doing so is generally considered to be superfluous.

Lime plaster is far more breathable than gypsum plaster. It not only allows moisture to escape and evaporate, but it also actually draws moisture out of the home.

Gypsum plaster is not very breathable. For this reason, it is significantly more ideal for ancient buildings with solid walls. This is because old buildings may hold a considerable quantity of water, which will result in damp issues when a product that is not breathable is applied.

Lime plaster is more flexible than gypsum plaster, and as a result, it has a lower risk of cracking in the event that movement takes place.

On the other hand, it takes lime plaster longer to set than gypsum plaster does.

How Does Lime Plaster Compare With Cement Plaster?

Sand, water, and cement are the three main components of cement plaster. Because it is more difficult to get a smooth surface with cement plaster than it is with gypsum plaster, a layer of gypsum plaster is sometimes applied on top of cement plaster even though it is used as an interior finish.

When compared to cement plaster, lime plaster possesses superior qualities in terms of breathability, flexibility, and environmental friendliness. In addition to this, it is an improved thermal insulator, and it creates a good bond with the wall.

Cement plaster, on the other hand, will set more quickly and is typically a more cost-effective alternative, both in terms of the price of the supplies and the amount of necessary labour.

Are There Any Modern Types of Lime Plaster?

There are currently a number of firms that create contemporary lime plasters with the goal of reducing the amount of time needed for the product to cure fully. These can frequently be applied in a single coat, eliminating the requirement for a scratch coat. Solo Onecoat from Lime Green is an example of a product that fits this description (opens in new tab).

You might also be familiar with the current trend of employing tadelakt in construction. It is a lime-based plaster that is frequently used in the Marrakech region of Morocco. It is ornamental as well as waterproof, and it has a smooth surface that appears to be similar to genuine stone.

It is available in a variety of colours and is perfect for use in bathrooms, where it provides a finish that is both attractive and functional on the walls and ceilings. Applying tadelakt plaster is a skilled talent.

Is Lime Plastering Difficult?

When it comes to plastering projects of any kind, including applying lime plaster to your walls, hiring a professional will be a much better and more time-efficient option than doing it yourself. Plastering is one of those skills that, while many people do try their hand at it, is undoubtedly one of those skills that seems easier than it is.

Plasterers who are talented in putting lime plaster can be harder to locate than those who are skilled in applying more modern varieties of plaster, but they do exist. Before hiring anybody, make sure you receive references from someone you trust.

A Hybrid Approach to Lime Plaster 

Plaster is no longer the material of choice for walls and ceilings since drywall has taken its place; yet, the look, feel, and durability of hand-applied plaster are not replicated by drywall.

Plastering in its traditional form is a time-consuming and difficult procedure; therefore, it should come as no surprise that plaster was swiftly supplanted by drywall as the material of choice for use in the construction of walls and ceilings in residential buildings in the United States.

Plaster was replaced by drywall because it was more functional, but drywall cannot mimic the appearance, texture, or durability of hand-applied plaster. Plaster, in contrast to drywall, can be moulded and troweled into virtually any shape or texture imaginable, making it a highly versatile and adaptable finishing material.

Lime plaster is one of my favourite kinds since it is durable, friendly to the environment, and attractive, and it has been used for finishing for millennia.

Lime plaster is created by combining sand, lime, and water. Due to its high index of refraction, lime plaster gives surfaces a warm glow that softly alters in colour and tone as the light moves throughout the day.

It's possible for even additional dimensions of interest to be added thanks to the textures produced by the sand and the plasterer's trowel technique.

In contrast, the one-dimensionality of the flat, smooth surface that drywall is supposed to attain in most parts of the United States is intentional on the manufacturer's part. When applied, texture frequently serves little purpose other than to imitate conventional plasters.

Still, we like drywall. It is an essential part of our hybrid plastering technique, which combines the effectiveness, availability, and strength of drywall with the aesthetic appeal of authentic lime plaster.

This allows us to take use of some of the positive aspects of each of these materials. Plastering with this technique can cost anywhere from $5 to $9 per square foot, depending on the specifics, level of difficulty, and size of the job.

This strategy requires more labour than the typical drywall installation method, but it is not nearly as arduous or expensive as the traditional method of applying three coats of plaster.

Drywall Replaces Lath

Drywall provides a solid base for lime plaster, and goes up faster than the wood lath of the recent past. The drywall is hung in standard fashion, but it doesn’t get taped, so we don’t worry as much about the number of seams and can use shorter drywall panels, which makes it easier to estimate and hang.

We utilise conventional drywall almost exclusively because it is intended to withstand the wetting caused by drywall compound and water-based paint, and it also withstands the wetting caused by lime plaster quite similarly.

We prime the drywall with a combination that consists of sand and Elmer's Glue-All, which is a PVA glue and is comparable to primers that are based on PVA. To provide the wall with some bite that will assist in holding the plaster, we roll and brush this slurry on exactly as we would paint.

Even though we hadn't had any problems with the lime plaster falling off when it was applied directly to the drywall, taking this additional step is a low-cost insurance policy, and it dries very quickly.

The blue board, which is designed to act as a substrate for veneer gypsum plasters, was erected in this project by a contractor who specialises in drywall work. We've come to the conclusion that the additional cost of a blue board isn't required, but it certainly doesn't harm either.

The Right Mix Is Key

Sand and hydrated lime make up the two basic components of the lime plaster that is being employed here. If you see this as being similar to a brick wall, the sand would represent the bricks, which would give the structure, and the lime would represent the mortar, which would keep everything together.

The sand must have a variety of grain sizes, but none of them should be any larger than around one-fifth the thickness of the plaster layer.

Additionally, the sand must be sharp and clean. When using coarser grain sizes, the plaster will have a more uneven texture; when using finer grain sizes, the finish will be smoother.

We normally use limestone sand for finish plasters because its light colour produces a brilliant plaster. We also use Type S mason's lime, which is typically available in 50-pound bags from local building supply yards.

When it comes to making a durable plaster that can be readily troweled on, getting the ratios of lime, sand, and water precisely right is really essential. In this procedure, the ratio of lime to sand shouldn't be any higher than 1:2, and it shouldn't be any lower than 1:4.

The ratio of sand to mason's lime Type S that was utilised in this mixture is one part lime to three parts sand. A very little amount of water should be added at a time until the plaster can be moulded into a ball that will not crumble when thrown and will adhere to the inside of the wheelbarrow wall when the ball is flung against it.

It is preferable to begin by adding too little water rather than too much since adding too much water will result in the formation of fine fractures in the plaster as the water evaporates and the plaster contracts.

The less water that is used, the less shrinking there will be. However, water is required to make the lime active and to create a plaster that can be worked. After the ingredients have been combined, you must wait a full day for the lime to become active while keeping it covered before applying the plaster.

Both of these ingredients may be acquired at local building supply yards. Enquire about the most up-to-date packaging; the longer the product has had the potential to be exposed to air and moisture, the less effective the contents will be.

Hydrated lime plaster, in contrast to cement stucco or gypsum plaster, does not harden until it is exposed to air and will retain its malleability continuously, provided it is protected from the atmosphere. This is similar to hydraulic lime, which may solidify even when submerged.

Hydrated lime may become harder in two different ways: first, it can become dry; second, and more significantly, it can get cured. Curing is when hydrated lime takes in carbon dioxide from the surrounding air and re-crystallizes it into limestone.

The process of making lime from limestone drives off carbon dioxide, but because CO2 is reabsorbed during the curing process, it’s a desirable material for green buildings.

Common Construction Methods

From the time of the Tudors until far after World War I, there was very little variation in the processes and components that were utilised in the production of flat plaster ceilings.

Oak or chestnut wood, which had been riven (hand-split) into laths, was utilised in the work that was of the highest quality. In subsequent years, cheaper alternatives like as fir softwood were used, and in the early 19th century, sawn lath began to replace riven lath. Riven lath had been the traditional method.

Laths were nailed to the bottom of the ceiling joists, leaving a space of about 10mm (3/8") between each lath, and the joints were typically staggered in bays that were a little over one metre (3' 6") in length to avoid lengthy cracks from forming in the plaster as it dried out.

Long, coarse water reeds were often used instead of wooden laths, particularly in regions where the reeds could be cultivated locally. These types of reeds are similar to those used by thatchers. Laths were used to fasten them to the bottom of the joists to a depth of roughly 12 millimetres (one-half of an inch).

To create nibs or keys, a "pricking-up" covering of lime putty and sand or earth mortars was applied, and then the mixture was forced through the lath. This coat had a normal thickness of 5-15 millimetres (1/4 inch to 5/8 inch).

The nibs provide the function of a mechanical key, assisting in the mortar's attachment to the lath. Reeds would have been used, in which case the initial layer of mortar would have been put directly to the reed, but it wouldn't have necessarily been forced through the whole thickness of the reed.

Lime putty needs to be a minimum of three months old before it can be used for restoration and repair work. Throughout history, numerous distinct kinds of sand would have been utilised, such as a combination of coarse and fine sand or whatever sand was readily available in the area.

The type of sand that is utilised for fine work at the moment is pit sand which has been cleaned and graded to a high standard. The typical ratio is one part lime putty to 2.5 parts sand, and it also contains hair from cows, horses, or goats at a rate of 2-4 kilogrammes (412 to 9 pounds) of hair for every cubic metre of mortar. Following the application of this, a three-pronged lath scratcher is used to scratch the surface.

After that, the plaster will start to dry, which will be followed by the beginning of the carbonation process. When subsequent coats are applied is determined by the temperature and the relative humidity.

A month is the typical amount of time needed for the first coat to dry completely. Before applying the second coat, the surface should be moistened if the first coat has become extremely dry and the second coat is to be applied.

The second layer, often known as the "floating" or "straightening" coat, is applied at a thickness of 10-15 mm (3/8"-5/8") using lime putty in the ratio of one part lime putty to three parts sand.

Additionally, hair would have been added, albeit in a quantity that was lower than the one used for the initial coat.

The second coat is ruled flat, and then a wooden float scours the surface to solidify it. After that, a "devil float," which is a hardwood float with nail points extending approximately 2 mm from each corner, is passed over the surface to provide a key for the final coat.

Before the application of the final coat, this surface also has to be dampened to control suction and ensure proper adhesion.

Typical Defects

The following items are probably the most prevalent contributors to the collapse or destruction of any ceiling, whether it is historical or not:

• failure of the timber
• the implementation of newly available services
• damage caused by the installation of fire-proofing material, damage caused by fire, damage caused by water damage
• bug infestation caused by damp/wet rot, dry rot, or both

Finding and fixing the problem that caused the damage should come first before any repairs are attempted. It is possible to salvage many ceilings, even those that appear to be beyond repair.

If it is not immediately clear what caused the cracking or the collapse, it is possible that the timber supports were flawed and contributed to the problem. If it is at all feasible, you should have someone walk on the floor above to check and see if the ceiling timbers bend in any way.

There is a possibility that the timbers that were employed were not of the appropriate size for the task at hand. Additionally, if the ceiling has a crack in it, look for evidence that dust is continually accumulating below the crack. This might potentially be an indication of movement in the joists.

If you want to do a more in-depth evaluation of the ceiling, it is advisable to look at the rear of the ceiling. You may do this in one of two ways: either by entering the loft area or by gently removing the floorboards in the room above.

An alternative that is very helpful is a digital inspection camera; however, to insert the camera lens, you will need to drill holes that are 8 millimetres in diameter.

At this stage, it should be feasible to determine what caused the damage and prepare for the necessary repairs.

Failures in timber can come in a variety of forms, including the following:

• Wrought iron nails may rust and fail because the surrounding timber is damp or due to prolonged exposure to the tannins in green oak; the presence of rusting fixings may be indicated by stains on the underside of the ceiling fire damage will be self-evident; however, if there is no damage to structural timbers, it may just be a case of a water leak.

• The persistent presence of moisture will induce salt and mineral migration, which will ultimately break down the integrity of the plaster and cause blowing (detachment of the plaster from the substrate). Water damage caused by leaking pipes may produce wet rot and slow ceiling drooping.
• The additional weight of the saturated plaster is frequently too great for the ageing laths to hold, which can lead to a partial or complete collapse of the ceiling. This is likely to occur if the ceiling has been damaged by water as a result of broken pipes.

Conclusion

Lime plaster is a traditional building material that has been used for centuries to create beautiful and durable finishes on walls and ceilings. It is made by mixing sand, water, and lime, and can be identified by its creamy white appearance.

Lime plaster is a "breathable material" that protects against dampness, making it a popular choice for older homes. Lime plaster has the potential to improve air quality, draw moisture out of the air, last for a long time, and is attractive to the eye. Lime plaster is more breathable than gypsum plaster, is more flexible, and takes longer to set than cement plaster.

It is ideal for ancient buildings with solid walls and is sometimes applied on top of cement plaster. Lime plaster is superior to cement plaster in terms of breathability, flexibility, environmental friendliness, thermal insulator, and bonding.

Modern types of lime plaster can be applied in a single coat, and hiring a professional is a better option. Plaster was replaced by drywall because it was more functional, but lime plaster is more durable, friendly to the environment, and attractive. Drywall replaces lath and provides a solid base for lime plaster, making it easier to estimate and hang.

The right mix of lime, sand, and water is essential for making a durable plaster that can be troweled on. The ratio of lime to sand should not be higher than 1:2 or lower than 1:4. The ratio of sand to mason's lime Type S is one part lime to three parts sand, and water is needed to make the lime active and create a plaster that can be worked.

Common construction methods include riven lath and sawn lath. Laths were nailed to ceiling joists to create nibs or keys, and lime putty and sand or earth mortars were applied to create nibs or keys.

Pit sand was used for fine work, and subsequent coats were determined by temperature and humidity. The most important details are that the first coat should dry completely, the second coat should be ruled flat, and the final coat should be dampened.

Typical defects include failure of the timber, implementation of services, fire, water damage, and bug infestation. Look at the rear of the ceiling to determine what caused the damage, such as rusting fixings, fire damage, water leaks, and wet rot.

Content Summary

• Lime plaster is a traditional building material that has been used for centuries.
• It's made by mixing sand, water, and lime and has been used to create beautiful and durable finishes on walls and ceilings.
• In this article, we'll be focusing on lime plaster ceilings and exploring their unique properties, benefits, and challenges.
• If you're considering a lime plaster ceiling for your home or project, it's essential to understand the basics of this material and its application.
• Check for the presence of sand and hair when attempting to determine the kind of plaster on your walls.
• Why, then, do people use lime plaster? It protects against dampness.
• It is a choice that is kind to the environment.
• It has the potential to enhance air quality.
• Plastering your home using lime plaster is often going to be more expensive than plastering your home with cement or gypsum.
• Applying tadelakt plaster is a skilled talent.
• Plastering in its traditional form is a time-consuming and difficult procedure; therefore, it should come as no surprise that plaster was swiftly supplanted by drywall as the material of choice for use in the construction of walls and ceilings in residential buildings in the United States.
• It is an essential part of our hybrid plastering technique, which combines the effectiveness, availability, and strength of drywall with the aesthetic appeal of authentic lime plaster.
• The blue board, which is designed to act as a substrate for veneer gypsum plasters, was erected in this project by a contractor who specialises in drywall work.
• The ratio of sand to mason's lime Type S that was utilised in this mixture is one part lime to three parts sand.
• Laths were used to fasten them to the bottom of the joists to a depth of roughly 12 millimetres (one-half of an inch).To create nibs or keys, a "pricking-up" covering of lime putty and sand or earth mortars was applied, and then the mixture was forced through the lath.
• A month is the typical amount of time needed for the first coat to dry completely.
• Before applying the second coat, the surface should be moistened if the first coat has become extremely dry and the second coat is to be applied.
• Additionally, if the ceiling has a crack in it, look for evidence that dust is continually accumulating below the crack.
• If you want to do a more in-depth evaluation of the ceiling, it is advisable to look at the rear of the ceiling.
• This is likely to occur if the ceiling has been damaged by water as a result of broken pipes.