Understanding The Lime Render
A lime render is a plaster or coating made from lime, sand, and water. It is a traditional building material used for centuries in construction and restoration projects.
When it comes to rendering their home, many people do not realise that lime render can also be an option. Some people are not aware of how important lime rendering on a wall can be. Lime render is a type of render mixed with lime materials that can be applied to the building’s wall to protect it from the elements. Rendering is the process of applying the product.
Old masonry buildings commonly require external wall rendering. Besides, it can be used with other building material types as well. Lime renders are traditional building materials made primarily from lime, sand, and water. They have been used for centuries in construction and restoration projects due to their numerous benefits and suitability for various applications.
Lime renders are highly versatile and can be used as external coatings on walls, interior finishes, or even for decorative purposes.
One of the key advantages of lime renders is their breathability. Unlike modern cement-based renders, lime renders allow the passage of moisture vapor, preventing the buildup of moisture within the walls.
This breathability helps to regulate humidity levels and prevent the occurrence of damp and condensation, which can be detrimental to the health of the building and its occupants.
Lime renders also possess self-healing properties, allowing them to accommodate minor structural movements without cracking, further enhancing their durability.
In restoration projects, lime renders play a crucial role in preserving the historical integrity of buildings. Many old structures were originally constructed with lime-based materials, and using lime renders during restoration ensures compatibility with the original materials.
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Benefits of Lime render
Lime render offers several benefits. Here are some of them which make you give lime a go whether you are renovating your home, exploring options, or working on a new building:
➜ Lime plaster is vapour permeable
Lime render is breathable due to the high vapour permeability. Air can pass through it in a way that is not possible with denser materials such as polymer-based renders of cement render. It allows the building to breathe so that moisture can escape its formation.
Moisture or water is the enemy of your home that can damage timber, iron, and traditionally built stone. Lime should be your first choice if you want to protect your building and retain structural integrity.
➜ Prevents condensation
When you use lime mortar for building, you will not see condensation on the surface walls. When used in limewash, lime has disinfected qualities, but the same is also true for lime renders mortars and plasters.
It resists the build-up of moulds that can lead to breathing difficulties creating a healthy environment for living. This makes lime render an ideal material for the building, especially when you and your family have any respiratory issues or allergies.
➜ Lime Render moves
Lime render is much more flexible than gypsum or cement renders. It means it can accommodate subtle movements, especially when used with animal hair or fibre in the mix. It is more resilient to cracking, which is useful if your house moves with the season, as most of them do.
➜ Environmentally friendly
Lime absorbs potentially damaging carbon dioxide from the atmosphere. The amount of energy required to produce it in the first place is lesser than what is required for cement production.
Besides, it can be produced on a small scale, not impacting the local area. Moreover, lime does not leach damaging chemicals as it is a natural material.
How to Lime Render?
When given little guidance and tuition, an amateur can also possibly render lime. However, the work needs to be carried out properly. When everything is perfect and straight, the traditional building rarely looks right. So, you can work knowing that it wouldn’t look out of place.
➜ Preparation of the Wall is the Key
The application, successful bonding, and hardening of lime render need the background to be free of containments, vegetation-free, clean, and dry all around the wall mass. The surface of the wall should be sound structurally, and the bedding and masonry must be in fine condition.
The different dubbing out coat application shouldn’t be considered as remedial to the brickwork or masonry background. The replacement of open joints or damaged or missing masonry must be repaired prior to the application of any dubbing coats.
Wherever you find unevenness or excessive hollowness, the areas must be rectified by applying lime mortar, and brick or stone slips into the mortar. It will result in a reasonably flat background surface before you commence rendering.
➜ Avoid the pitfalls of lime rendering
Lime renders don’t require due care during their application. They can fail from shrinkage, weather damage or drying back too quickly during their early stages.
But, when applied properly, they will offer both decoration and protection to any structure. You can avoid failure through basic preparation. Besides, observation and planning are also strongly recommended at the outset.
➜ Bonding and Suction Control
Whether hydraulic or non-hydraulic, it is crucial to check the suction degree before you apply the new hydrated lime coating. Excessive or poor suction can lead to weak bonding with the substrate caused by quick drying of the applied render.
It will result in powdery and weak interface resulting in failing and separation at later stages. You require to bond the coating to the substrate.
Wetting down is required near waterproof masonry or dense blocks when you want to control the suction. Use a mist spray to dampen the surface but only on porous ones like old brickwork.
Before you start to render, wet the wall using a hose from top to downwards. It may also require to be carried out several times a day.
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Why Do You Need Suction Control?
The main purpose of the suction control is to accomplish a damp surface and not a wet one. The surface should not have standing nor running water on the brick or masonry as it forms a barrier between the substrate and the coating.
Moreover, the lime mortars stiffen and adhere across a certain suction amount.
For the waterproof or dense background, applying a lime or sand splatter dash coat or harled coat may be vital for the mechanical key.
Lime Rendering Techniques – How To Apply Lime Render?
First Coat (Bonding Coat)
Apply uniform thickness of lime render of around 9 to 12 mm on any surface. It is suggested to throw, cast or harl to get the best results. Cast-on coat materials should be wetter and grittier than normal rendering.
The thrown coat of traditional lime will offer an appropriate bonding coat for the scratch coat. It provides a superior bond from casting on and is less likely to delaminate from the substrate. It greatly emphasises impervious surfaces like engineering brick or granite and porous surfaces like soft brick or cob.
Though lime mortars are quite cohesive, they require more effort than cement renders. Apply the first coat, especially on brick buildings using a laying-on trowel and pressure to press it into or on the wall. The application must be uniform and should not be straightened or overworked too much.
Second Coat
The second coat is known as the floating coat. It is used to straighten to make sure an even and flat surface. After it, the coat is scoured up with a polyurethane or timber float. In normal conditions, it takes about a week.
There is no such rule, but damp surfaces take longer to harden up. The work is further straightened to produce the desired level of render finish.
After the render is set, rub up with a normal float and end with a devil float score slightly.
Final Coat
Known as the setting coat, the final coat is treated the same as the previous coats, assuming any straightening required has been carried out before the finish coat. Avoid rubbing up the work too soon after it has been laid.
Try to leave it for as long as possible. Topcoat plaster will have more lime content and finer sand. If you work on lime mortars too soon, it results in the puling of free lime to the surface. It may lead to failure as the properties of the material are compromised.
Besides, the thickness of the topcoat plays an important role. It shouldn’t be thicker than 5 to 7mm.
Some applications use natural hydraulic lime renders. The technique is the same as mentioned in the above guidelines. If lime putty is used, the render may be smoother and more consistent.
Lime plastering or rendering is a great option for your house. Avoid the use of modern paint to lime render. Avoid the use of modern paint to lime render because modern paints don’t provide the same breathability as lime render.
This is a critical factor for older, traditional buildings as it helps to reduce moisture content within the walls and prevents mould growth. If you want to get the lime render done for your home in the UK by a professional, you can contact us.
What does lime do in render?
Lime plays a crucial role in render by providing a range of beneficial properties. When used as a binder in render mixes, lime acts as a hydraulic material, allowing it to chemically react with water and carbon dioxide from the air.
This reaction, known as carbonation, results in the formation of calcium carbonate crystals, which contribute to the strength and durability of the render. Lime also offers excellent breathability, allowing moisture to evaporate from the render and preventing trapped moisture from causing damage.
Are there any disadvantage of lime render?
While lime render offers numerous benefits, it has a few disadvantages. One disadvantage is its relatively slower drying time compared to modern cement-based renders.
Lime render may be more susceptible to damage from harsh weather conditions, especially in areas with heavy rainfall or freeze-thaw cycles.
Lime render can be more expensive than other types of renders due to the specialized materials and craftsmanship involved.
Is lime render better than cement?
Lime render offers several advantages over cement render. One of the key benefits of lime render is its breathability. Lime allows moisture to evaporate, preventing trapped moisture from causing damage to the underlying structure.
In contrast, cement render tends to be less breathable, which can lead to moisture issues and potential structural damage over time.
Lime render is also more flexible and accommodates slight movement in the building, reducing the risk of cracking.
Lime is a natural and sustainable material, making lime render an environmentally friendly option. Its traditional aesthetic appeal and compatibility with historic buildings further add to its desirability.
Is lime render waterproof?
Lime render is not inherently waterproof. However, it possesses some water-resistant properties. Lime is a porous material that allows moisture to evaporate, which helps prevent moisture buildup within the wall system.
Lime render on its own may not provide complete protection against water infiltration. To achieve the desired level of water resistance for particular projects and environmental conditions, it is essential to seek expert advice and adhere to appropriate application methods.
