Building conservation masterclass

Conservation and Repair of Stone Masonry with Nick Durnan

Ref: B3D09133

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Places available

About this course

This course provides a comprehensive study of building and decorative stone from its formation and extraction through to its repair and maintenance in the building context. The programme includes basic geology of building and decorative stone; a detailed description of decay mechanisms of limestone, sandstone, marble, slate and granite; traditional construction methods; modes of failure; large and small scale repair options; cleaning methods, surface treatment and remedial work; specification and costing.
The teaching is divided between illustrated lectures and practical instruction. It makes use of the Ruinette, the purpose-built structure incorporating many of the faults found in historic masonry, enabling students to practise repair and remedial techniques. These include cutting out, repairing in stone and mortar, raking out joints and repointing and preparation and placing of mortars. Instruction is provided in some basic laboratory techniques, including recognition of stone samples and analysis of mortars.

Course Description

Day 1

Evening Welcome talk and introductions. Explanation of course, background of tutors, student introduction.

Lecture. Introduction to historic stone masonry. Range of stone and masonry types

Day 2

Morning Lecture. Geology, characteristics, and use of some common building and decorative stones

Introduction to the Ruinette, health and safety issues, examination of hand samples

Lecture. Technology of lime

a) traditional and historic practice. Local production, lime burning, slaking lime and mortar mixing

b) traditional stone construction - facing, through stones and core work

c) changes to traditional practice: hydraulic lime, Roman cement, Portland cement, lime putty mortars, modern hydraulic lime

d) lime cycle - chemistry of lime: raw materials, burning, slaking, carbonation

e) selection of lime, aggregates, pozzolans for conservation and repair mortars

Demonstration and practical. Joint treatment

a) preparing joints for re-pointing

b) preparing mortar

c) placing mortar

Afternoon Discussion of repair techniques

Viewing the Ruinette and discussing the repair of stone buildings, when to replace, piece-in, tile repair, mortar repair or consolidate. Criteria for such decisions. Choice of material, surface texture and tooling.

Demonstration and practical. Mortars repairs for stone

Explanation, demonstration and practical

a) preparing stone

b) armatures and support

c) design of mortar

d) mixing, placing and curing

Practical hands-on session - repairing stone with mortar

a) preparing stone

b) fixing armature

c) mixing mortar

d) placing first coat of mortar

Day 3

Morning Lecture. How and why stones decay

a) characteristics of stone types - porosity and permeability, pore size distribution, mineralogy, bedding planes, crystal structure

b) causes of decay i) - salt crystallisation, frost damage, chemical change of minerals, expansion/contraction, water abrasion

c) causes of decay ii) - poor selection of stone, poor detailing, rusting iron fixings, hard dense mortars, plant growth, lichens and algae, impervious coatings, new stone beside old

d) durability - careful selection and observing bedding planes, nonferrous fixings, compatible mortars

Display, explanation and demonstration of stone working

a) quarry tools

b) masonry tools and templates

c) carving tools and drawing

d) working a stone face, different tooled finishes

Practical hands-on session - cutting out and repairing stone with stone

a) marking out area to be repaired

b) cutting away stone to be replaced

c) fixing new piece with precision

Afternoon Practical hands-on session - cutting out and repairing stone with stone

a) marking out area to be repaired

b) cutting away stone to be replaced

c) fixing new piece with precision

Practical hands-on session - repairing stone with mortar

Placing second coat of mortar

Day 4

Morning Lecture. Survey and recording of stone masonry. Repair options, trials and specification. With case studies

Demonstration and discussion. Examination of hand samples, identification of common stone types

Practical hands-on session

a) completing cutting out and repairing stone with stone

b) completing mortar joints

c) completing repairing stone mortar

Afternoon Lecture - Case studies of recent conservation and repair work at Wilton House and Salisbury Cathedral

Course review and questions, recommended books, organisations, further courses, HE booklets and HS pamphlets.

Issue of certificates and depart.


Arrival Day - this is the first date listed above

Courses start early evening. Residential students to arrive from 4pm, non-residential students to arrive by 6.45pm.

6.45pm: Welcome, followed by dinner (included).

8 - 9pm: First teaching session, attendance is essential.

Daily timetable

Classes 9.15 - 5pm, lunch is included.

From 6.30pm: Dinner (included for residential students).

Evening working - students may have access to workshops, but only with their tutor's permission and provided any health and safety guidelines are observed.

Last day

Classes 9.15am - 3pm, lunch is included.

Residential students are to vacate their rooms by 10am please.

(This timetable is for courses of more than one day in length. The tutor may make slight variations)

Course Materials

What students need to bring

  • Please remember to bring work clothes/overalls and shoes/boots for practical sessions. A torch and umbrella may be useful on the short walk to the Auditorium and Ruinette.


Nick Durnan

Nick Durnan - BCM Course Leader

Nick Durnan originally trained as a stone mason at Canterbury Cathedral and went on to study for a degree in carving and conservation at the City and Guilds of London Art School.


Residential option available. Find out accommodation costs and how to book here.

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