Structural Repair of Traditional Buildings
by Patrick Robson
Donhead Publishing, Ltd., Shaftsbury, Dorset, UK; 1999; reprint, 2005
312 pp; hardcover; numerous diagrams; $79
Reviewed by Judy Hayward
Professionals who have the gift of sharing a discipline’s overview while backing it up with important details are hard to find. Donhead Publishing is a reliable source of finding such practitioners who can also write. Engineer and author, Patrick Robson, MSc, CEng, FconsE, MAE, FIStructE, MICE, MaPS, has mastered the goals, science and craft of restoration work. He has filled Structural Repair of Traditional Buildings with information that students, teachers and professionals will find useful when diagnosing and fixing structural deterioration regardless of the side of “the pond” on which they find themselves at work.
The book is carefully written and divided systematically into five parts: “The Basics,” “Defects,” “Options,” “Management,” and a very helpful set of Appendices. Robson does not rely on photographs at all but on line drawings that illustrate everything from the forces of nature to how to avoid a fall from a jobsite ladder. By relying on drawings, he stresses the process of studying and resolving any building’s problem and does not confuse the reader with the specifics of given historic structures. His six-step process emphasizes evaluating the causes of damage by studying the indicators of performance, either good or poor. The steps are observing the building, considering potential cause(s) for the problem(s), listing typical symptoms of the probable causes, gathering or testing performance indicators, matching symptoms to indicators, and finally arriving at a decision about the cause(s).
In Figure 7.2, he illustrates the breadth of items to observe, suggested tests to determine the nature and extent of symptoms, and property records to review. Upon gathering all this data, a matrix can be established to record causes and symptoms (indicators) helping the investigator to arrive at one or more causes of the structural problem. Figure 7.3 is a sample of a simple matrix.
Chapter Five gives an excellent overview of the context of conservation work. Here, Robson provides seven straightforward principles that should guide preservation or conservation work anywhere in the world:
“Ensure that all work has local planning authority consent.”
“Do nothing unnecessary.”
“Avoid damage to cherished details.”
“Match materials like for like.”
“Avoid modern materials if possible.”
“If modern materials have to be used, avoid clumsy disguise.”
“Use reversible methods of repair if possible.”
Robson offers seven chapters comprising Part Two, “Defects.” Chapter Eight features an impressive list of the causes of structural damage. He segregates the parts of a building from foundation to roof and the common causes of damage for each concluding with a list of what can go wrong with the whole building.
Chapter Nine features information about soils, groundwater, erosion, excavation and the impact of wayward tree roots. Most of the chapters in this section delve into the relationship between the structure and its natural environment. He reminds us that human beings can cause significant damage and loss of equilibrium with seemingly simple alterations: cutting joists, new wall openings that are not properly supported, and temporary propping are a few problematic and frequently occurring human interventions.
He also addresses the impact of fire on structures and chemical reactions in building materials that can contribute to structural failure. For the most part, Robson addresses problems with traditional building materials but he also cites the pernicious problem of chemical attack on concrete in Chapter 14. He succinctly warns of failures in high alumina cement, the impact of carbonation on iron reinforcement of concrete, calcium chloride additives, salt spray in marine environments, two types of sulfate attack, alkali-aggregate reaction, and the presence of iron pyrite.
Chapter 15 is a must read for any student of structural engineering or preservation. The cogent descriptions of biological, physical and chemical causes of deterioration are a good overview and warning for anyone in historic preservation work. The reader will finish this section with an appropriate level of wariness about how existing buildings can fail over time.
After giving us the means to figure out what can go wrong and why, Robson comes to the rescue with Part Three, “Options.” He believes that one must define the purpose of repair and get everyone – owners, funders and the professionals on the team – to agree before the work begins. “Part of the skill of the repairer lies in early recognition and definition of constraints (such as the need to keep the building in use) and opportunities (such as solving non-structural problems during the structural repair contract, and sharing overheads). These should form part of the planning. One point is sometimes more obvious to owners and funders than to their professional advisors: repair competes for funding with other financial options, including the option of leaving the money in the bank.”
The book delves into typical repairs in the third section, “Options,” with detailed information on timber frames, masonry, foundations, weak materials and restraints, usually created by the junctions of building materials that give a building additional strength. The reader is likely to read this section, and others as well, once and then refer to it again and again when working on projects. For example, in Chapter 20, “Masonry,” Robson provides a helpful guide to repairing cracks. Dimensions are given in the metric system but can easily be converted to the English system for U.S. practitioners.
Health and safety are also stressed throughout the book and in an appendix. Robson also provides practical strategies of thinking through the troublesome possibilities before executing the work and recommends identifying every hazard and rating its likelihood and severity to develop a program to mitigate hazards to people and structures. The matrixes and processes are not likely to be shared with clients. They are developed to help the professional arrive at a meaningful diagnosis, the right solution, and a safe worksite for the repairs.
The fourth section of the book, “Management,” has good information for facility managers on preventive maintenance. Robson stresses that this is the best long-term economic strategy as well as the best strategy for allowing the building and its materials to perform over time. He compares preventive maintenance and maintenance on discovery in one of his succinct charts in Chapter 23. The chart should be required reading by boards of directors for institutions charged with the care of important historic structures. “Discovery” is a euphemism for lack of maintenance leading to typically costly and sloppy reactions to a discovered problem.
Only a seasoned practitioner would be wise enough to conclude the book with a chapter titled, “Surprises.” Robson is indeed a seasoned practitioner. The last two sentences of the book’s last paragraph summarize the advice and process the reader has just absorbed with a simple, straightforward warning, “…hence the need for investigators and repairers to have a sound knowledge of defects and material behavior, and an appreciation that, with existing buildings, knowledge is always incomplete. Surprise has to be expected.”
Judy L. Hayward is executive director of Historic Windsor, Inc. and the Preservation Education Institute. She is the education director for Restore Media’s Traditional Building Conference Series and can be reached at email@example.com or 802.674.6752.