What is Hydraulic Lime?

Hydraulic lime is a natural substance that is found in the ground in areas which have high deposits of calcium. Unlike non-hydraulic lime the high level of calcium means that hydraulic lime has an ability to set under water and as well as by absorbing CO2 from the atmosphere. This makes it particularly useful for using as a protective wall covering as it sets far more quickly than no-hydraulic lime and is therefore highly crack resistant.

History of Lime Render in Construction

Hydraulic lime render and mortar was introduced into Britain over 2000 years ago by the conquering Romans who were aware of its durability and suitability for use as a building material. In fact lime was used by the ancient Egyptians to sculpt large statues and figurines and examples have been found in the ancient Egyptian burial chambers as well as in the Great Wall of China. Suffice it to say that lime render has an unequalled track record of performance and durability and was the material of choice in Britain until the early 18th Century.

During the 18th Century portland cement was discovered and as well as being cheaper to produce it set far more quickly than non-hydraulic lime and could be applied by a less skilled dauber or plasterer than was needed to apply a lime render. Hence lime renders fell out of fashion and portland cement based renders and mortars became the norm.

This has been the case until recent years when the UK Government became concerned at the environmental affects caused by the large amounts of CO2 that cement manufacture produces and also the effects on the fabric of a house that are caused by a waterproof and non-breathable material like cement. As a result the Government spent several hundred thousand pounds investing in research to find a less environmentally damaging substitute and one which wolud allow structures to breathe unlike cement. The result of this independant research came up with Hydraulic Lime.

Why is Hydraulic Lime Better?

1. It enables walls to breathe and allows internal moisture to escape boosting air quality.

2. It acts like a sponge in absorbing driven rain and releasing it as moisture keeping internal walls dry.

3. It is softer than cement renders and therefore moves with the property meaning no need for movement joints and an ability to self-heal cracks. Especially good for timber framed construction.

4. It is carbon neutral as it absorbs CO2 to compensate for that produced in its manufacture.

5. Hydraulic lime has a setting time at least the equal of cement renders and reduces application costs.

6. Comes in a variety of colours due to modern pigmentation techniques.

7. Particularly effective against frost and salt attack and driven rain making it ideal for properties exposed to the elements.

8. Fully compatible with traditional building materials such as wattle and daub, hemp or straw bales.

9. Fully re-cyclable material when a house is taken down.

10. Aesthetically flexible with a variety of different textured finishes.