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Heritage Restoration - Lime Mortar, Bonded Stone Walls & Stone Buildings

Background

Before approximately 1930 all stonework, including stone walls and stone buildings  were constructed using lime mortar and it is these structures that we  consider today to be of heritage significance, requiring specialist heritage craftspersons in their maintenence, restorations and reconstructions. 

Considerations

When considering bonded stonework always consider the correct use of a specialist lime mortar. We have undertaken many bonded stonework projects using lime mortar and a number of re-worked con-tracts where previous contractors had used cement mortar at considerable strength, the result being blown faces of surface stone i.e., the strength of the mortar was higher than that of the stone and during expansion of stone, the faces of visible stone had fallen off leaving unsightly stonework.

Although lime mortar is more expensive, it is more pliable than cement mortar and enables expansion and contraction of stone; lime mortar also allows the movement of water and water vapour by drawing out ingressed liquid or vapour from stonework.

Lime Mortar 

Traditional lime mortar, sometimes referred to as natural lime mortar are made using proportions of sand and lime,  the lime acting as a binding agent.  Throughout history, in the construction of traditional stone buildings and stone walls, there have been two basic types of lime mortar used: hydraulic lime mortar and non hydraulic lime mortar.

Hydraulic Lime Mortar

Hydraulic lime mortars are classified according to there setting times and final strength into three categories: 'feebly hydraulic', 'moderately hydraulic' and 'eminently hydraulic', the latter having the fastest setting and highest final stength.

Additives called 'pozzolans' such as brick dust can be added to hydraulic lime mortars, improving substantially their setting times and  final setting strengths.

Non Hydraulic Lime Mortar

Made from almost pure forms of lime and reacts with carbon dioxide in the air, binding and taking a long time to set from a basic strength over several weeks, to full strength which could be a number of years.

Stonework constructed using lime mortars allows settlement of the structure without cracking of stone or building structures during the settlement period, and for a long period of time the lime mortar remains somewhat pliable, allowing for further settlement.

Bonded Stonework - Overview of Categories

For many years we have and continue to provide specialist bespoke services for  a range of lime mortar bonded stonework for stone walling and stone buildings which fall into the following mortar bonded stonework categories:-

Rubble

The stone is generally not dressed, or roughly dressed and the mortar joints are generally wide, ranging from one inch to five inches, but can be raked to enhance the stone . Rubble stonework can be divided into:-

Random stonework - uncoursed or brought to courses stone walling. 

Squared stonework - uncoursed, built to courses or regular coursed stone walling.

Micellaneous stonework  - polygonal stonewalling, flint stone walling or Lake District Masonry.

Ashlar

Stone walling consisting of carefully dressed or wrought stone with narrow lime mortar jointing at around 1/8th of an ich thick.

Our stone builders work to "stone with mortar", not "mortar with stone", the former bringing out the shapes, texture and beauty of natural stonework. 

Dyes can be added to the lime mortar ranging from buff to charcoal, further enhancing the colouration of the stone.

Contact us for more information on lime mortars for your bonded stonework.

...Our barn conversion, mortared stonework and lime mortared stonework and stone builder  services are available in Preston, Lancashire, the UK and wider Europe.  Our regional stone builder  services are:  stone builder in preston,stone builder in lancashire, stone builder in Lancaster, stone builder in Blackburn, stone builder in Bolton, stone builder n in Burnley, Stone builder in Clitheroe, stone builder in Chorley ...