The float coat (also known as brown coat) is applied on top of the scratch coat and is also made with a coarse aggregate. The rough scratched finish provides a good key for the following coat to adhere. It is made with a coarse aggregate to leave a rough surface, this is then heavily scratched (hence the name scratch coat). The scratch coat is the first coat applied to the substrate, this could be bare masonry or laths. Non-hydraulic lime plaster assume warm, dry weather and may be significantly longer. Lime plasters are always applied and built up in thin layers called coats, the traditional three coat system is the recommended method: However, it is quite 'fatty' and therefore sticky, it is easier to apply to ceilings and laths. Non-hydraulic lime plaster can stay wet indefinitely in damp conditions where there is no opportunity to carbonate. It sets very slowly by carbonation and typically cures in around 12 months.

This plaster is extremely soft and flexible, perfect for conservation of delicate masonry.

Made with non-hydraulic lime, commonly known as lime putty. Non-Hydraulic Lime Plaster (Air Lime, Non-Hydraulic) However, it cures in around 90 days (typically) which means it can be painted with a breathable coating much sooner than other lime plasters.

Hydraulic lime plaster is less fatty than other lime plasters and may require more effort to apply to laths and ceilings. Made with hydraulic lime, this will set in damp conditions and may be required in extremely damp conditions such as cellars where a non-hydraulic lime plaster would not carbonate sufficiently. Hydraulic Lime Plaster (Water Lime, Hydraulic) The moisture will generally find a way out in some isolated areas and manifest itself as a damp problem. Once a non-breathable material is added to solid wall, large amounts of moisture can become locked in. If you are experiencing damp issues in an older building, it could have been replastered with a modern gypsum plaster or may have been covered with a non-breathable coating like an emulsion or even a wallpaper. The moisture is eventually expelled and the masonry gradually dries once the root cause of the damp is located and fixed. In that case, you may have avoided long term problems with damp in the building.ĭamp issues tend to be short lived where masonry is fully breathable. If you own a property that was built before 1950 then there's a good chance it is finished with lime plaster. Solid walls behave like a large sponge and can absorb a large amount of water in the event of a leak or flood there is no cavity to stop the transfer of moisture as you'd find in a modern building. This makes lime plaster hugely beneficial in old buildings with solid walls. Not only does it allow moisture to escape and evaporate from the structure, it effectively draws moisture out from the structure thanks to its exceptional capillary properties. Unlike the modern gypsum plaster found in most homes today, lime plaster is breathable. It may also contain a reinforcement fibre such as animal hair which can serve to strengthen the material and bind it tightly to the underlying structure. It is a mixture of traditional lime, sand and water. Lime plaster is the name given to a lime mortar that is applied to cover internal walls and ceilings, it has been used to finish interior surfaces for thousands of years. Suppliers of Lime Mortar, Lime Plaster & Building Conservation Materials 01642 430 099 The Lime Plaster Guide What is Lime Plaster?

Limestone plaster