Another Log in the Wall: Preserving Historic Timber Architecture in Alberta

“Sustainability is not possible without durability […] Once constructed a building becomes a machine that ‘needs to be fed’.” -Joseph Lstiburek, 2006

In Alberta, there are hundreds of thousands of square feet of raw uncoated timber used in historic architecture, including farmhouses at the Ukrainian Cultural Heritage Village and log churches at Historic Dunvegan. Penetrating oils and wood coatings help prevent the primary causes of wood deterioration, but when these historic structures must be preserved in perpetuity, how do you assure the building material will last when it was originally built to make it through only a decade or two?

This is where Alberta Culture and Tourism’s Conservation and Construction Services comes in.

In the summer of 2017, in my role as Heritage Conservation Technologist, I received the Martin Weaver Student Scholarship from the Association of Preservation Technology International (APTi) to help support a long-term monitoring project to evaluate the performance of wood preservative coating systems, using both laboratory work and a test wall. This study is considered “preventative conservation,” which includes cyclical maintenance and sustainable financial planning. This study will help evaluate the feasibility of cyclically applied coatings in consideration of site values, change of colour and texture over time, economic viability, environmental concerns, and worker safety in application. A variety of promising sacrificial (preventative) coatings have been selected for use on raw untreated historic timber architecture.

Don’t let this above graph of tens millions of dollars distract you, often our assets and projects are far more humble. Even the treatment of an outhouse can offer long term dividends, after all we have a few dozen to take care of across the province:

There has been much new research in the performance of penetrating oils and a variety of other wood coatings as sacrificial layers that prevent the primary causes of wood deterioration: fungal and bio-growth, insects, UV, and the erosional forces of water, wind and ice. However, more information is needed on different regional environments, local species, and wood section/grain direction as defined by building component use (shingle/log/siding). Also, much of the research is coming out of the United States, where higher Volatile Organic Content (VOC) formulations are acceptable. Another important part of this research are those formulations with lower VOC’s that are acceptable in the Canadian context.

Eight test walls of four species used in historic timber architecture in Alberta (Pine, Tamarack, Spruce and Aspen) will give east-west and north-south weathering exposures of 7-10” diameter logs. In-situ testing will be supplemented with laboratory characterization and measurements (Accelerated Weathering, Water Vapour Transmission, Fourier Transform Infrared Spectroscopy, X-ray Photoelectron spectroscopy, Scanning Electron Microscopy/EDX, Microscopy, Spectrophotometry, and Mechanical Bending Tests) of coating and substrate decay patterns and performance. These tests will help qualitatively describe and metrically quantify the performance of coatings. The test wall will also be supplemented by live weather monitoring (temperature, humidity, UV, rain, wind direction and speed).

In a very practical sense, the goals of this study are to determine which product type performs best. Furthermore, their performance will determine whether or not these products should be applied to our buildings, and if it is a cost-effective way of preserving Alberta’s material heritage. The broader goals of this project includes exciting interest in applied conservation science. It is providing opportunities for students to research real life problems and to further our understanding and strategic use of test walls for the process of specifying the best conservation treatment possible. Further treatment testing of a variety of materials, more collaborations, and grant writing will likely follow.

Written By: Evan Oxland, Heritage Conservation Technologist

This project was funded in-part by APTi. For providing equipment, facilities and laboratory testing, a very special thanks to partners from the University of Alberta’s Forestry Program, Heritage Division Curatorial and Creative Services, Royal Alberta Museum, University of Alberta and the National Institute of Nano Technology, and the National Research Council.

Sources:

Lsitburek, Joseph. Building Science Digest. “Increasing the Durability of Building Constructions.” 144. 2006.

Magill, Courtney. Performance Assessment and Evaluation of Hydrophobic and Ultraviolet Protective Treatments for Historic Log Structures. (Masters Thesis) University of Pennsylvania, Philadelphia, PA.