Understanding the composition of an existing mortar is an important first step when repairing, repointing or restoring a historic or traditionally constructed building.
Roundtower’s Mortar Analysis Service provides a detailed examination of existing mortar, render or plaster samples. The findings can help architects, conservation professionals, contractors and building owners develop a compatible repair specification based on the characteristics of the original material.
Using a replacement mortar that is too strong, too dense or insufficiently vapour permeable can alter how moisture moves through traditional masonry. A professional mortar analysis helps reduce this risk by providing evidence about the original binder, aggregate and overall mortar composition.
What Can Mortar Analysis Identify?
Depending on the condition of the sample and the level of analysis required, the investigation may include:
- Identification of the original binder type
- Assessment of whether the binder is non-hydraulic, naturally hydraulic or contains other reactive components
- Estimation of the original binder-to-aggregate proportions
- Identification of the aggregate type, colour and particle characteristics
- Aggregate grading and particle-size distribution
- Identification of visible inclusions or distinctive markers
- Identification of animal hair, plant fibres or other reinforcement
- Assessment of the degree of carbonation
- Investigation for soluble salts
- Macro-photography showing the sample’s structure and identifying features
The completed analysis is supplied with a written report setting out the findings and, where appropriate, an interpretation of what those findings may mean for the proposed repair work.
Why Is Historic Mortar Analysis Important?
Traditional masonry buildings were generally constructed using relatively soft and vapour-permeable lime mortars. These mortars were intended to accommodate small amounts of building movement while allowing moisture to evaporate through the mortar joints.
Replacing an original lime mortar with a significantly stronger or less permeable material can place additional stress on the surrounding stone or brick. It may also concentrate moisture within the masonry rather than allowing it to escape through the joints.
A mortar analysis can help establish the characteristics of the original material and provide a more reliable basis for selecting a suitable replacement mortar.
The objective is not necessarily to reproduce every component exactly. Instead, the findings help develop a repair mortar that is visually, physically and technically compatible with the existing building fabric.
Suitable for a Range of Conservation Projects
Our mortar and render analysis service is suitable for:
- Historic houses and traditional cottages
- Protected structures and listed buildings
- Churches and ecclesiastical buildings
- Castles, forts and archaeological structures
- Stone boundary walls
- Traditional brick buildings
- Lime-rendered façades
- Internal lime plasters
- Conservation and heritage grant applications
- Repointing and façade repair projects
- Building pathology and moisture investigations
Analysis may also be useful where several different mortars are present and it is necessary to distinguish the original material from later repairs.
A Targeted Approach to Mortar Testing
Not every project requires the same level of investigation. A relatively straightforward repointing project may require basic identification of the binder, aggregate and approximate mix proportions, while a more complex conservation project may require additional examination of salts, fibres, carbonation or unusual inclusions.
We will discuss the building, the proposed work and the available sample before confirming the most appropriate level of analysis. This targeted approach avoids unnecessary testing while ensuring that the report provides useful information for the repair specification.
From Mortar Analysis to a Compatible Repair Specification
Once the existing mortar has been assessed, Roundtower can assist with the selection of an appropriate lime binder, aggregate and mortar specification.
Consideration should also be given to:
- The type and condition of the masonry
- The hardness and porosity of the stone or brick
- The building’s level of exposure
- Joint width and depth
- Existing moisture and salt conditions
- The required colour and surface texture
- Whether the mortar will be used for bedding, repointing, rendering or plastering
Where appropriate, sample panels or trial mixes should be prepared before the main work begins. This allows the proposed mortar to be assessed for colour, texture, finish and compatibility with the existing masonry.
Arrange a Mortar Analysis
Before sending a sample, please contact the Roundtower technical team with information about the building and the proposed repair work.
We can advise on selecting a representative sample and confirm the appropriate level of analysis for your project.
Contact Roundtower today to discuss mortar analysis, mortar matching or the preparation of a compatible lime mortar specification for your historic building.
