The benefits of using lime based mortar, as opposed to Portland cement, is as simple as this: lime Mortars have been used for thousands of years and stood the absolute test of time. Whereas, cement is a little over 100 years old and still having the same problems with cracking and brittleness it has had since day one.
For most builders, the suggestion that an old-fashioned, slow-acting and softer material is superior to one that is modern, hard and acts fast, is to be met with suspicion at the very least. All cement has quicker drying times, is suitable for certain situations and much great architecture that would not have been dreamt of without it. It is one of the biggest reasons why jobs all around the world, in particular Western Australia, have suffered from horrific cracking and in some cases drummy. In extreme cases, the render has popped off the walls. This is due to the lack of understanding about cement and its properties when mixed with water.
At PJK Plasterers, we use high lime, low cement ratios that give a better, more consistent finish and has all the great properties of lime. High-lime renders work as simply as this: when the render is set, and the larger particles of lime and cement have set, there are still tiny lime particles known as free lime, this free lime is allowed to move within the render and, if a crack appears, the free lime will move into the crack and heal it. This process is called Autogenous healing.
Getting the mixes right for a particular situation is crucial, and we have many years of experience in judging this.