Mortar is a binder and a filler. Historically the binder was lime the filler was sand, well for at least 6,000 years – or so we believe. Clay is also a binder and whether or not it is mixed with sand it has an equal long or longer history of use for building.
This was not so much a function of choosing one material over another, rather it was choosing what was readily available and from experience worked well.It is a function of location, geology first and foremost determines what can and cannot be used for building, Exposure, location and environment dictates what will be durable and what will not.
In the UK the majority of our surviving functional historic buildings are masonry with lime and sand mortars, plasters and renders. Where timber was the principle structural member, lime and sand plastering on laths or wattle and daube are the most common survivors and in the Chalk downs of the souther coasts, rammed earth finished in lime is common.
There are pockets of most of the variety of these building types doted here and there throughout all parts of the British and Irish Isles, but unquestionably the weather determines what survives and what disappears more than anything else.
The Romans brought building masonry with Lime to Britain and Ireland and it has remained ever since. Prior to that, timber and dry stone walls were the predominant building materials and that tradition and history of building has had a significant influence on our built heritage ever since.
Dry stone building in areas of the British and Irish Isles is among the finest examples found anywhere in the world, indeed the great celtic brooches pre-date the pyramids by some one thousand five hundred years. These were mortar less walls and since no archeological evidence of lime mortars walls pre-date the Roman occupation, timber, cob, clay and dry stone construction were the only methods used.
In many areas, masonry was buit with clay cored mortared walls finished with lime and sand plaster or pointing.