Many of the buildings found up and down the UK provide a window into history. They are symbols of the hard work and dedication that tradesman throughout the ages put into their work. Many have seen us through natural disasters, iconic battles and moments of financial depression. And, in countless instances, they play host to some of the most significant moments in our country’s history. Although we live in a world where high-rise flats and a rolling construction industry means we are constantly striving for modern design, the influence of historic buildings is something that cannot be ignored.
This is the reason why many companies, including the team here at Limebase, dedicate their services to the preservation and restoration of historical buildings. Many of the materials we create have a deep history, embedded into that of ancient lands and civilisations. And, with that, they carry a host of benefits for their use in historical preservation. This guide takes a look at three lime-based options and delves into their importance for such a purpose.
The Importance of Historic Preservation Materials
One could ask, why do we focus so heavily on the use of historic preservation materials? Afterall, the construction industry has moved on so far in the last 200 years, why not focus on the more reliable and secure materials we use everyday? The importance here comes from the need to preserve as much of the original structure as possible.
Whether restoring an old building for historical merit or rebuilding an older family home, traditional building methods allow you to hold on to the structure’s authenticity. For nostalgia reasons, the same hands that once applied plaster to freshly built walls come back to life. The sweat and energy that went into every inch of masonry work rejuvenated when one chooses to use a similar mix of mortar, plaster or render. There is a level of respect held for the people who lived throughout the years which comes from reflecting materials and construction methods that are true to the building’s birth.
On a practical level, it is also an environmentally responsible practice to renovate historical buildings accurately. Many already benefit from a range of energy efficient features including good ventilation and strength. By holding on to the frame of a building, we reduce the expenditure of energy used to knock it down and rebuild. Historical buildings, particularly those created with lime, have been shown to consume 75 – 90% less energy than modern-day cements. Therefore, we minimise the expenditure caused producing new building materials.
Many historical building materials have their own range of benefits too, not available with modern options. Lime, for example, does not completely harden or set. Therefore, it allows for movement in older buildings. Cracks in lime-based mortar tend to be smaller and can ‘self-heal’ overtime as rainwater dissolves away free lime and this becomes deposited throughout the wall. Lime-based walls are highly breathable, allowing moisture to evaporate. This reduces the likelihood of damp and mould. Therefore, there are many benefits to sourcing the most authentic material for any historical renovation.
What are the main Historical Building Materials to Consider?
Depending on the area of the UK, building materials vary widely. This was mostly due to the availability of different sands, stones and binding agents. One modern day example of this can be found in Bath, Somerset. The iconic Bath stone is an oolitic limestone which dates all the way back to the Jurassic period. It is honey-coloured and has become a visual icon of the local area, largely due to its high abundance and availability in the area.
Many building materials share the same history, found and used for their local abundance. However, lime-based products are ones found all across the UK in different forms. Limebase are one of the leading suppliers of such products, many of which are produced in-house and using lime from specific locations such as Singleton Birch in Lincolnshire. Below, we take a look at three of the most versatile materials, looking into their history and most common uses.
A brief history of lime plaster
Lime plaster is one of the most commonly found finishing materials on UK buildings during the second half of the 17th century. It is traditionally composed of a sand, water and lime blend. Many older samples also include horse hair which was said to give reinforcement. For this reason, the finish has a textured surface unlike the plaster we use today but one that was relatively commonplace.
It has been found on buildings from all over the world, notably, those in Jordan said to have been built around 7200 BC. There is also evidence that the Ancient Egyptians were some of the first civilisations to use lime. Traditional plaster has been even been found on the pyramids at Giza, built over 6,000 years ago. In fact, this sustainable ‘green’ product was one of the most highly used finishing materials in construction right up until the 1950’s when plasterboard and gypsum plaster took precedence.
As with all building materials, there are benefits and disadvantages to lime plaster. Key benefits include:
- Once set, lime plaster still has a degree of flexibility and movement to it. This minimises cracks as the building moves over time.
- It is less impacted by water and will not soften or dissolve like drywall.
- It has a strong and durable finish which makes it ideal for exterior use.
- Lime plaster can be used to protect softer materials from external stresses.
- It has an elevated pH which provides a degree of fungicide protection, minimising the risk of mould.
- Traditional non-hydraulic blends can cause chemical burns with a high pH or 12. However, this acidity drops to approximately 8.5 once dry.
- It requires moisture to set properly and must be kept damp for several days – adding to labour costs.
A Brief History of Mortar
Mortar has long been a standard choice for bricklaying. As far back as the Egyptian period, builders would use gypsum-based mortars to loosen large stones as they were moved into position. The earliest mention of lime mortar was around 4000 BC when it was used on the iconic pyramids themselves. Over the years, many advances were made with the traditional blend including adding in pozzolanic earth to provide heightened strength. In 1796, James Parker patented what he called ‘Roman Cement’. Here limestone and clay were burnt together and the resulting product stored in waterproof containers. This was then used on buildings where the walls were prone to high moisture.
By some reports, lime mortar was ‘officially’ invented in 1794 by Mason, Joseph Aspdin, and patented as Portland Cement in 1824. When blended with lime, this produced the perfect blend of strength and workability. Mortar has been used for a range of applications from binding building blocks to adding decoration to masonry walls.
Again, lime mortar has a range of benefits and disadvantages to the users. These include the following:
- Lime mortar is designed to be weaker than the bricks themselves. This means it can be removed easily and replaced without damaging the wall around it.
- Blends containing impure limestone are said to speed up the setting process.
- It is more breathable than traditional mortars and allows moisture to escape through evaporation. This minimises the risk of cracks and mould.
- Lime mortar is said to last longer than Portland Cement. It is made from 99% pure calcium which has a minimum life expectancy of 100 years.
- As with many lime-based products, mortar takes longer to harden. This can also be an inconsistent process which produces ununiformed finishes.
- Many mortars develop their strength over time (anywhere between 90 – 360 days). Therefore, a project will take longer to complete.
A brief history of limewash
Noted as one of the older paints through history, limewash is just as widely used today as it was back in Ancient Egypt. It is a simple form of matt paint, traditionally made using lime and water. To achieve different colours, mud and earths are mixed into the blends. The metal oxides within these materials produce alkali-resistant pigments. And, this variation usually goes hand-in-hand with where the paint is produced – for example, Suffolk limewashes tend to have a pink hue to them.
Limewash has long been used as a decorative finish, suitable for both internal and external walls. It is commonly used over lime plaster, render, earth walls, limestone and timber alike.
Some of the key advantages of limewash include:
- Limewash is suitable for use over the entire building.
- Can be personalised to the location of the building.
- It is a more breathable option to modern day paints with a vapour permeable rating of 350 units. This prevents water and moisture from becoming trapped in external walls. Left untreated, this can cause decay within the masonry and timber.
- It has a low opacity and unique surface glow.
- It is inexpensive and solvent-free.
- Deters wood-boring beetles and essentially ‘sterilises’ the walls
- As each blend is entirely unique and naturally made, limewash is notoriously hard to match in colour.
- It does not serve well in very fast-drying conditions.
- Limewash required additional care during application to achieve the best results.
Understanding the Right Historical Preservation Materials to use
When it comes to choosing the right materials, it is vital you discuss any project with restoration experts. The consultants here at Limebase have over 30 years of experience in this field, including time spent restoring/supplying/consulting iconic buildings such as Exeter and Salisbury Cathedral. Get in touch today for more advice and recommendations into the various construction materials out there.