Earth Mortars Blog

Historic Environment Scotland (HES) published a blog on earth mortars in Scotland in 2022. It provides an overview of our knowledge and understanding of this material and includes links to resources available.

Earth Mortars Research – Baseline Report

HES commissioned research to establish a baseline of knowledge on the extent, character and significance of Scotland’s earth mortar heritage and condition of current conservation practice. A literature review and stakeholder engagement were undertaken, and an earth mortared structures database and stakeholder network established. Completed by ArcArchitects and ReBearth, the Earth Mortars Research Report sets out 29 general research recommendations and 13 specific recommendations on themes of identification, recording, analysis, conservation technique, materials, skills, statutory controls and transition to net zero.

A section of a wall that reveals an earth mortar.

Understanding Earth Traditions in Orkney

The Earth Mortars Research Report identified a knowledge gap relating to the use of earth materials in Neolithic Orkney. HES commissioned ArcArchitects and ReBearth to complete a benchmarking exercise to address this area. The project brought together earth building specialists and archaeologists to share knowledge and expertise on the extent of the resource, sourcing patterns, preparation/modification processes and technical use.

ArcArchitects and ReBearth undertook further detailed research into earth traditions in Orkney through Earthbound Orkney. Funded by HES, National Heritage Lottery Fund and the Society of Antiquaries and in partnership with the University of Highlands and Islands, the project took a multi-disciplinary approach to reach wider audiences across the art, heritage and construction sectors.

Earth Literature Review

HES commissioned independent researcher Dr Vanessa Reid to work on a literature review of scientific analysis of turf and earth-built structures. This covers soil mechanics and factors contributing to decay, as well as methodologies for earth analysis. The report sets out a number of case studies and identifies 10 knowledge gaps and 10 methodological issues to help direct future research. These include: 

1. There has been little scientific characterisation of earthen building materials to help inform sourcing earth for conservation repair.
2. Scientific techniques need to be used in a targeted manner to provide a baseline and usefully inform earth analysis, conservation and management, and technical guidance.

Earth Mortar Analysis and Identification

HES commissioned independent researcher Dr Vanessa Reid to work on this ongoing project and address some of the issues identified in the Earth Literature Review. The project aims to baseline knowledge and inform future best practice guidance. British Standard BS EN 17187:2020 provides guidance for a common methodology for characterisation of mortars used in cultural heritage, but has limitations: 

• it does not differentiate workflows based on material type,
• it does not provide guidance on pre-treatment,
• some significant techniques such as Particle Size Distribution are missing.

A proposed methodology for earth is in development, subject to further optimisation following additional data interpretation. Pre-treatment processes were identified as being crucial for successful analysis and data interpretation. Next steps involve inclusion of additional analysis techniques. Best practice guidance is being developed, whilst the project outcomes are also contributing to the mortars database.

Vernacular Hutting – exploring approaches to sustainable construction

The Grass Roots Hutting project used construction of a hut to explore how traditional materials and skills can be used to make construction more sustainable. All materials came from within a few 100 yards of the site. Research into natural, social and cultural capital accounting embedded aspects of traditional craft skills, intangible heritage, climate action, building resilience, community empowerment and training. A film and a blog about the project are available.

Funded by UKRI Social Research Council, the project was delivered by University of Edinburgh, Archaeobuild, Comrie Croft and HES.