Roman Cement

Roman Cement 

Before the widespread use of Portland cement ,exteriors were often rendered with Roman cement. Although a variety of products were used,they were essentially what we would today call hydraulic limes .It would probably be classified as an NHL 5 or "eminently hydraulic lime."This may be a little problematic since this was the 19th century, when many small companies made different products under the heading of cement The classifications were not so clear and the products not so  controlled.

I do recall when I was working as a young plasterer in the late 1970s we worked on facades in Maida Vale in Central London and none of the plasterers knew how to repair the mouldings .One older Irish plasterer, who was still working in his eighties managed to make the repairs (really easily as I remember, much to the delight of us youngsters as we teased the other more experienced men for weeks) Mack the older man. explained to me that the original work was done with Roman cement and he said he remembered it being delivered in small barrels He said you could always recognise it since it was brown /red, I wished I had listened .

Roman cement was used with aggregate to run mouldings, render facades and for castings. The material is particularly useful for casting, since it sets quickly but it needs some preparation for rendering.There are modern versions available from companies in France and a lot of great work has been done in both production and application of  Roman cement in Poland.

Roman cement bracket

mould for bracket

Case mould for bracket

Roman cement used for pilasters
Peckham South East London

Detail of Roman cement
 note the poor
state of the OPC repair 

Facade finished with Roman cement
Peckham South East London

Ashlar jointing or blocking out

Detail of Rustication 

Detail of ashlar jointing

Textured hydraulic lime