To retouch the small adult bedroom decor or the exterior of the house, the use of lime is very common. It is most often used for wall coating. The material can replace not only mortar cement but also plaster.
It is full of countless remarkable advantages. Besides its environmentally friendly qualities, it stands out for its protective function when you plan to coat a wall.
Among hydraulic lime nhl, air lime paste, slaked lime calcium hydroxide or hydrated lime, there are several types of lime available on the market. Discover in this article the essentials to know about this product.
📋 The essentials at a glance: Personally, I consider lime to be the essential breathable material for any sustainable renovation, as it allows about 80% of water vapor to pass through. For me, it is the best natural barrier against moisture. This millennia-old product sanitizes your walls while offering a structural flexibility that cement will never have.
What is lime and its uses?
Before developing the different uses of lime plaster or limewash, it is appropriate to provide you with the definition of the material.
In magazines or on the internet, you may sometimes have heard about calcium oxide lime. This is because this product is chemically calcium hydroxide or calcium oxide.
It can be obtained by calcining limestone. It mainly consists of calcium carbonate.
When you heat limestone rock to 800 °C, it becomes quicklime. Then this transforms into slaked lime calcium hydroxide by adding water.
When you mix it with water and sand, you get lime mortar. Then it solidifies upon contact with air or water to regain its original state.
Depending on the cooking method and the geological formation of the calcium carbonate limestone rock, lime is distinguished by its distinctive properties.
The hydraulic lime product derived from clay-type limestone hardens upon contact with water. On the other hand, air lime hardens upon exposure to air.
As for its uses, lime is one of the most ecological and oldest materials in construction. It can be used both in decoration and masonry.
Although it has been replaced by cement since the 20th century, it is gradually making a comeback today, thanks to its multiple qualities.
🎒 On site: During my first project on a stone wall in 2021, I made the mistake of working under 30-degree heat. The lime dried too quickly and ended up powdering. The lesson is clear: always moisten the surface the day before and avoid high temperatures to ensure proper setting.
Air lime and hydraulic lime are highly prized when renovating an old building. This material is perfect for preserving its characteristics.
It can also be used during tile installation, wall coating, base coat plastering, and screed composition.
For recent houses, hydraulic lime plaster adds an aesthetic touch. Many homes have facades covered with lime. At first glance, it has the ability to catch the eye of passersby.
Besides that, it helps to reinforce stone or brick constructions. It is not surprising that it is favored during the restoration of historic monuments.
🌍 Did you know? Lime “heals” itself. In case of micro-cracks, rainwater dissolves some free lime which recrystallizes in the crack, naturally sealing it over time.
What types of lime are available?
| Type of lime | Recommended use | Final hardness |
|---|---|---|
| NHL 2 | Very soft substrates (earth, brick) | Low |
| NHL 3.5 | Common masonry and plasters | Medium |
| NHL 5 | Foundations and damp environments | High |
| Aerial lime | Interior finishes and decorations | Very flexible |
There are several names concerning lime. Mortar aerial lime, calcium hydroxide lime aerial lime paste, hydrated lime, slaked lime calcium hydroxide powder and many others, it can be confusing.
To simplify things for you, we can categorize 2 types of lime, namely aerial lime and hydraulic lime.
Also known as slaked lime, the first is available in paste or powder form. It sets upon contact with air. With few impurities, it offers several uses.
Aerial lime in paste or powder form is ideal for thin plaster, paint, interior finishing, mortar and more. If used outdoors, it is only suitable for areas sheltered from wind and not exposed to rain.
As for hydraulic lime NHL, it is made up of silicates, aluminates, and calcium hydroxide. It contains up to 30% clay. Its setting can be faster than that of aerial lime. It sets upon contact with water.
Hydraulic lime is mainly used for masonry and also for thick plasters. Resistant, it is suitable for outdoor use as well as indoors including in the bathroom, the attic and loft, the cellar and some damp rooms.
What are the environmental benefits of lime?
👍 Strengths:
– Vapor permeability
– Sanitizing properties
– Great durability
🔍 Limitations:
– Corrosive handling
– Quite slow setting
– Sensitive to frost
Compared to cement, concrete, and other building materials, lime has environmental advantages.
Aerial lime hydraulic lime, any calcium oxide lime is both an ecological and healthy product. It is free of VOCs, biocides, and solvents. In its pure state, it remains compatible with any natural product.
Lime is also a breathable material because it is permeable to water vapor. It allows walls to breathe. That is why it is highly valued in the restoration of old buildings.
That’s not all; it allows moisture to escape and facilitates hygrometric exchanges. It has the power to repel and capture water vapor. Many professionals use it to combat rising damp.
Due to its elasticity, lime prevents cracks. It has good fire resistance, which guarantees its durability.
Unlike cement, the composition of hydraulic lime aerial lime is environmentally friendly. By modifying the chemical properties of the soil, the processes use a natural resource.
The temperatures used to fire clay-containing limestone are lower than those used in cement production.
How to apply a lime plaster?
Before answering this question, it is important to explain how to make lime plaster. To do this, equip yourself with a smoother, a trowel, and a mixer.
Start by putting the sand into a concrete mixer. To make fine plasters, it is advisable to use fine sand with a grain size of 0.1 mm to 0.2 mm.
Then gradually add the lime and finally pour in the water. All you have to do is let the mixer run to obtain the plaster. Besides lime and water, this decorative coating can include dye and silica.
Hydrated lime calcium hydroxide powder, slaked lime calcium hydroxide, hydraulic lime NHL or aerial lime paste, no matter the name, the application of lime remains roughly the same.
It is advised, before taking action, to properly prepare the wall the day before. Remember to sprinkle it with water. The surface must be clean, sound, and in good condition.
⚠️ Warning: Never spray lime on a wall already painted with acrylic paint or a waterproof coating. Without mineral adhesion, your plaster will eventually peel off in sheets in less than 2 years.
That said, lime plaster is generally applied in 3 layers: the bonding coat, the body coat, and the finishing coat.
The first is known as gobetis. It must be thin, creating a texture. The second serves to hide irregularities and protect the wall. The third ensures the final appearance of the plaster.
Between the application of these layers, you must always respect the drying time often mentioned on the product packaging. Once the last layer is dry, you can pass a slightly damp sponge to smooth the surface.
💡 Practical tip: For a homogeneous mix, always pour the water first into the concrete mixer, then the lime, and finally the sand. This prevents lumps from forming at the bottom of the drum.
How does lime help in the restoration of old buildings?
Do you want to renovate a facade? The product containing calcium hydroxide air lime hydraulic lime can be useful to you. Especially since it is an old house, this material will suit you perfectly.
Between air lime putty, slaked lime calcium hydroxide, hydrated lime, and hydraulic lime nhl, the latter is particularly suited for the restoration of old buildings.
Thanks to its flexibility, it follows the movements of the building and retains its distinctive characteristics. Despite the hardness of stone walls, this calcium oxide lime CAO fits it perfectly.
Whether used as an exterior coating or as a component of mortar, it helps optimize the support’s resistance. If you apply it on a facade, the lime has the ability to protect it from rain, wind, and humidity.
If you want to bring a touch of freshness to your heritage, know that this product is very decorative. By mixing it with natural pigments, it offers you a wide palette of tones.
How to use lime as mortar?
Lime mortar has several advantages. Its main asset lies in its flexibility, which simplifies its application. It should be noted that it is also a breathable material. This allows it to easily evacuate water vapor.
Making it is child’s play. Like cement mortar, it requires the addition of an aggregate such as sand and water.
To carry it out, put 3 buckets of sand and one bucket of slaked lime into a wheelbarrow. You can then pour in the water. Use a shovel to thoroughly mix the mortar.
The more the components blend, the more the lime dries. So you need to add water slowly. Keep stirring the mortar until you get a uniform texture. This process usually takes a maximum of 15 minutes.
Once the air lime mortar is well prepared, you can use it for masonry or for making coatings. It is also used in the improvement of historic buildings or old houses.
Calculate the nombre de sacs de 35kg nécessaires :
Besoin estimé : sacs de chaux
What are the safety aspects related to the use of lime?
Whether you use lime milk, slaked lime water, air lime hydraulic lime, any calcium oxide lime is a corrosive material. It is therefore strongly recommended to handle it with care.
You are advised to wear personal protective equipment to limit potential risks. Equip yourself with protective glasses and an appropriate mask.
For work at height, it is reasonable to entrust the task to a professional if you suffer from vertigo. Otherwise, use a sturdy and reliable ladder. The tool allows you to easily reach all corners.
