What is Lime?

A sedimentary rock – limestone – formed from the compressed remains of bones of prehistoric creatures and shells – all of which are Calcium Carbonate (CaCO). Lime is produced by burning limestone, chalk or shells at a high heat and was used in Ireland for building for over a thousand years. Lime kilns were widespread – as much for agricultural reasons as for building. When heated to 900 degrees ‘quicklime’ results, and this was used extensively to raise alkaline levels in acidic boggy soils. Limestone was refered to in Irish as ‘cloch aoill’- manure stone. In those days the process of converting limestone to ‘quicklime’ would take about three days and three nights, and a kiln would be constantly in production for months on end. Strong and durable – above is a door arch that was crafted three centuries ago using Lime. These days only very small number of big, modern kilns exist – but none are in Ireland. Lime mortar is composed of lime, sand and water.

A vastly under rated material despite it’s excellent record, lime has the ability to self heal, mending cracks within itself, unlike cement which is brittle & once cracked becomes ever more vulnerable to invasion by the elements.

Because Lime is flexible it allows stonework to settle into it’s rightful groove, there is no risk of  cracks serious anyway.

Lime’s wonderful permeability lets moisture be drawn away from a house wall instead of locking dampness within the very stone or brick, as cement does.


Ecologically speaking, Lime is reversible & recyclable.

It requires lower (than cement) temperatures in its production therefore spends less energy.

Through carbonation Lime is able to re-absorb carbon dioxide created when burning limestone – and even leaves a negative carbon footprint when combined with such plants like hemp for example, which is used as render when mixed with Lime.

In the past Lime was mixed with ox or horse hair and applied to internal walls creating an insulating coat, many layers of which were built up  over time can still be seen in old buildings today.

For more information on the history of lime kilns see Brian Kaller’s excellent article

white wash over dresserdecades of lime wash

15 thoughts on “What is Lime?

  1. Ohhh, thank you sooo much for visiting my blog! I have the loveliest memories of riding my horse to the Buena Vista Winery in Sonoma, California as a teen, ground tying him at the fountain, and ducking into the limestone caves where the wine was cellared to take refuge from the heat of summer!

  2. When in Wales I was at Porthclais in Pembrokeshire and saw a commemorative sign regarding the limekilns there – I didn’t understand then the importance, uses, history of it all – you have enlightened me.

  3. I have only just discovered your absolutely amazing blog – and wonderful pictures – thank you, so much. It has gone onto my desktop as a ‘must keep.’

  4. Dear Limewindow, Spent the afternoon reading your blog. Posted earlier too, re semi-ruined (actually, who am I kidding? fully ruined; ) cottage in Connemara I am tempted to jump into. What I’m looking at is about 60 square metres. I’d be aiming to do it simply and slowly and well, and planning to be available as a gopher labourer, possibly with friends’ help also, alongside the skilled workers of the area. I have two questions. Did you do lime and hemp insulation or other? Or did you bother with insulation? And if so / if not, how has that panned out? THe second question I hope won’t strike you as invasive. I’m a writer and lover of old places, have been visiting the spot I want to restore in for 16 years, and spend 1/4 of my year bringing groups there as part of my working life as things stand. All the ingredients are there for me to make this work. The imponderable is how much it’s going to cost, even in the loosest sense. It’s on an island, to boot, which I know will add in region of €10,000 transport costs. I’m scouring all around me at the moment trying to get rough per squar emetre costs for doing the kind of job you did. If you have a second and the incllination, my email address is yvonnesworkshops@gmail.com if you would be prepared to let me know a thing like this. Thanks a million, again, for the blog. It is fantastic! (As is the house!) Finally, would you ever let a very curious restoration-planning visitor in for a cup of tea to handsel the feel of a place done this way? Best wishes for now! Yvonne Cullen

    1. Yvonne thanks for your comments and enthusiasm – certainly if you are able to visit Donegal we can arrange to meet and you can see the limewindow cottage for yourself. There are lots of developments in the world of the “lime revival” which I mean to write about soon as I get time. In terms of your own dream I hope you can see from this project that all is possible. The walls of the cottage are not insulated but the roofs pace has sheep’s wool in it. I shall drop you an email on the subject of cost. This project was a rebuild not a renovation as such, using the footprint and recycled stone of the old thresher barn. If the roof of yours is long gone then it’s going to be a rebuild too, for even if walls are standing, the hearting material (inside the wall) is probably washed away & there wouldn’t be enough stability to support a new roof. Advantages of a rebuild is laying foundations ( mostly they are absent). Happy dreaming.
      Louise

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