Lime Stuff

Frequently Asked Questions

Below are some of the questions we frequently get asked. If your question isn't answered below, please give us a call on 01794 884294 and we'll be happy to offer you further advice and guidance.

What are the benefits of using lime?

Lime has been used for centuries as a traditional building material.  The 1970s saw a decline in its use as cement, and more notably Ordinary Portland Cement (OPC) was introduced.  OPC was favoured for it's ease of use, quick setting qualities and durability.  However, this durability means OPC is almost impermeable to moisture. The result is moisture is trapped, leading to dampness and decay of timbers.

Lime plasters, by contrast, are open and porous materials, allowing vapours in and out of the walls. This helps to stabilise the internal humidity of a building, making for a more comfortable environment, reducing surface condensation and mould growth.

What are the differences between hydraulic and non hydraulic lime?

Limes when used in building can be categorised into two types, either Hydraulic (Natural Hydraulic Limes) or Non-Hydraulic (Lime Puttys).

Hydraulic limes set by hydrolysis, a reaction caused by water.  It causes a faster and harder set, therefore these limes are more often used for exterior work, especially in exposed or damp conditions.  Hydraulic limes are available as a bagged powder and in differing degrees of strength.

Non Hydraulic Limes are putties and set by carbonation.  This causes a much slower set and the lime remains softer and more breathable.  Our non-hydrualic lime putties are matured on site and used to produce our medium, coarse and fine set plasters and mortars.

How do I mix hydraulic lime? Hydraulic Lime recipe

A standard drum mixer can be used to mix hydraulic lime, although a roller pan or paddle mixer is preferable for larger projects. 

In an empty mixer, add 1 part sand, followed by 1 part lime and then 2 parts sand.  Mix dry for at least 5 minutes.  Gradually mix in the water until the required consistency is reached.  Mix for a further twenty minutes.

Which type of paint is suitable for use over interior lime plaster, lime wash or lime rendered walls?

For interior walls and ceilings that contain lime, EARTHBORN CLAYPAINT is ideal because unlike most other paints, it does not reduce the breathability. Conventional vinyl emulsions would partially seal the surface, causing potential problems for the building fabric and the likelihood of the paint ‘blowing off’. Claypaint allows the walls to breathe and offers a viable alternative to lime wash.

A few simple steps should be taken before applying Claypaint to a lime surface:

Lime render or plaster needs to be fully cured before painting. As a general guide allow at least 1 month curing for every 5mm of thickness. In poor drying conditions this time period may be extended.

Before painting make sure the surface is stable (not flaky or powdery).
Slightly moisten the surface before applying the first coat of paint – a water spray bottle is perfect for this.

When painting onto cured new interior lime plaster, dilute the first coat of Claypaint with around 20% water followed by a full coat.

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