Hydraulic Lime vs Non-Hydraulic Lime
What is Lime Plaster?
Lime plaster, a type of lime mortar applied to coat interior walls and ceilings, has been utilized for countless centuries as a finishing material for interior surfaces.
This mixture comprises traditional lime, sand, and water, and occasionally incorporates reinforcing fibers like animal hair. These fibers not only enhance the material's strength but also ensure a secure bond with the underlying structure.
Why use lime plaster?
Lime plaster offers a captivating array of natural colors and textures that enhance the aesthetic appeal of any space. From subtle earth tones to vibrant hues, lime plaster provides a versatile palette to suit various design preferences. Its unique texture ranges from smooth and polished to textured and rustic, allowing for creative and visually interesting finishes.
In contrast to the contemporary gypsum plaster commonly found in today's homes, lime plaster offers a breathable characteristic. It not only permits moisture to escape and evaporate from the structure but also possesses exceptional capillary properties that effectively draw out moisture.
This attribute makes lime plaster highly advantageous for older buildings with solid walls. Such walls act like a substantial sponge, capable of absorbing a significant amount of water in the event of a leak or flood. Unlike modern constructions that feature a cavity to hinder moisture transfer, solid walls lack this barrier.
If your property was constructed prior to 1950, there is a good chance it is finished with lime plaster. In such cases, you may have avoided long-term damp issues within the building. Damp problems tend to be temporary in structures where the masonry is fully breathable, as the moisture is eventually expelled and the masonry gradually dries out once the root cause of the dampness is identified and resolved.
However, if you are encountering damp issues in an older building, it is possible that it has been replastered with modern gypsum plaster or covered with a non-breathable coating such as emulsion or wallpaper. Once a non-breathable material is applied to a solid wall, a significant amount of moisture can become trapped. This moisture often finds isolated areas to escape, resulting in the manifestation of damp problems.
Types of Lime Plaster:
Crafted using non-hydraulic lime, also known as lime putty, this type of plaster possesses exceptional softness and flexibility, making it ideal for conserving delicate masonry. Its setting process occurs gradually through carbonation and typically takes approximately 12 months to fully cure. Non-hydraulic lime plaster has the ability to remain moist indefinitely in damp environments without the opportunity for carbonation. However, due to its slightly "fatty" consistency, it exhibits a sticky nature, which actually simplifies its application on ceilings and laths.
Created using hydraulic lime, this type of plaster possesses the ability to set even in damp conditions, making it particularly suitable for areas with high moisture levels such as cellars. Unlike non-hydraulic lime plaster, hydraulic lime plaster can carbonate effectively in such environments. Although it has a lower fat content compared to other lime plasters, applying it to laths and ceilings may require a bit more effort. However, one notable advantage is its relatively quick curing time of approximately 90 days, allowing for the application of a breathable coating at an earlier stage compared to other lime plasters.
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