All Things Lime
Eden Hot Lime Mortar are specialist providers of Hot Lime Mortar and mixes. Browse our product range covering Air Lime, Hydraulic Lime, Natural Hydraulic Lime, and Hydrated Lime. Read more about why you should use hot lime mortar
Why Use Lime Mortars and Plasters?
Lime is more flexible than gypsum or cement, so is less likely to crack when plastered on walls or used for mortars or repointing.
Until the beginning of the last century most buildings were constructed with lime. Many of those now remaining have been repaired in recent years using Portland cement based mortars and renders often with the following consequences:
Until the beginning of the last century most buildings were constructed with lime. Many of those now remaining have been repaired in recent years using portland cement based mortars and renders often with the following consequences:
- All buildings move, especially those pre-1900 which had less solid foundations. Cement mortars and renders are rigid and crack under stress. Often cement is stronger than the masonry – transferring fractures into surrounding brick or stonework.
- Cement due to its high density and crystal structure is ‘non porous’. Cement renders will crack eventually allowing water into the wall with little ability for the water to evaporate. In the case of cement mortars the evaporation can only take place through the masonry. This may result in increased spoiling of soft stone and brickwork leaving the mortar standing proud like a shelf, to collect more water, increasing the masonry’s deterioration. In addition walls will get damp resulting in internal mould and unhealthy living conditions.
- Chemical action between brick or stonework and cement can take place causing unsightly salt staining and in the case of some sandstone very rapid spoiling.
To some extent modern methods of construction have reduced, but not entirely eliminated these problems. With modern and older buildings therefore there are good reasons for using lime mortars, since:
- Walls breath better and moisture can evaporate.
- Mortars and renders do not set too hard.
- Thermal movement can be accommodated without damage.
- Expansion joints can often be avoided.
- Insulation is improved and cold bridging reduced.
- No risk of salt staining.
- Alterations can be effected easily and masonry re-used.
- Masonry life is increased.
One other reason for using limes relates to their environmental benefits. Because they are easy to remove, lime mortars allow recycling of valuable masonry units such as bricks, which have high embodied energy.
- Calcium carbonate – also known as: chalk, limestone, agricultural lime chemical formula: CaCO3
- Calcium oxide – also known as: quicklime, burnt lime chemical formula: CaO
- Calcium hydroxide – also known as: hydrated lime, slaked lime chemical formula: Ca(OH)2
Lime Terminology in Building
- Air Lime – Air lime, or high calcium lime does not have any hydraulic component. It can be quicklime for slaking or hydrated lime. It gains strength slowly, by combining with atmospheric carbon dioxide to form calcium carbonate (as per the lime cycle). Several grades of air lime are identified in EN459 the European standard for Building Lime.
- Hydraulic Lime – Lime with hydraulic or cementitious properties which will set when exposed to moisture. Several grades of hydraulic lime are identified in EN459 the European standard for Building Lime.
- Natural Hydraulic Lime – Hydraulic lime which does not contain any performance enhancing additives. Its properties are as a result of the mineralogy of the calcium carbonate stone which is quarried for burning.
- Hydrated Lime – Hydrated lime is NOT Hydraulic lime and will not set in contact with water.