Lime and Mortars in the Conservation and repair of Historic Buildings by Peter Ellis
Posted 10th March 2020
Cowdray Ruins 2005-2007 and Hampton Court Palace 2005-2006.
The importance of using the appropriate lime.
I first became aware of Cowdray when reading the Chapel Plaster Consolidation case-study in the excellent English Heritage Technical Handbooks by John Ashurst in the late 1980s, and was therefore delighted to be asked to advise on the repair mortars for the major conservation and repair project at the 16th century Palace ruins. This was timely – the Practical Building Conservation Series is being revised and to be republished (in ten volumes), but it also coincided with the sad passing of the hugely influential John Ashurst.
Cowdray, in Midhurst (West Sussex), constructed in the 1520s on the site of an earlier 13th century Manor House (Coudreye), is an exquisite early Tudor courtiers palace, frequently visited by Henry VIII. During refurbishment in 1793 a devastating fire largely destroyed the house and it has since remained a romantic ruin painted by both Turner and Constable. Repairs by St John Hope in 1909-14 – cement/lime blend pointing mortars, concrete lintels to door and window openings, and tile capping to exposed wall-heads – are credited with saving Cowdray from total collapse.
Mortar samples were collected from most areas of the original build and all known (with thanks to Oxford Archaeology Ltd) phases of alteration and repair. An unusual feature of the original Cowdray mortars (and plasters) is that these yellow clay/sand mortars had changed colour where they had been in close proximity to the fire in the same way that yellow Raw Sienna pigment becomes red Burnt Sienna when heated. All tonal gradations of yellow through pink to dark red mortars were present in the mortars according to the intensity of, and proximity to, the heat and flames