For the Continued Preservation of Log Buildings
“Preserve for the future instead of the moment.” – Harrison Goodall
At the beginning of October, I (Casie Radford) attended Montana Preservation Alliance’s (MPA) Conference on the Preservation and Stewardship of Historic Places. The conference, held at Yellowstone National Park’s historic Old Faithful Inn, was dedicated to the preservation and rehabilitation of log and rustic structures. Approximately 100 attendees, with different backgrounds and levels of experience with log construction, traveled from all over the country to learn about the charm and challenges of historic log structures (Image 6).
To summarize the conference in four words: preventive maintenance is critical. Log buildings are rarely as grand as the Old Faithful Inn Old House (Images 1-4, 7). While there are thousands of log buildings that have stood for over 100 years, their original builders did not intend for these buildings to last forever. Therefore, the desire to preserve them has created a self-inflicted challenge. Since the design of most log buildings was poor to begin with, as described below, we are faced with the decision of whether or not a building has enough historic significance to make the complex labor that goes into saving it worthwhile.
Preventative maintenance mitigates some of these concerns. As a general rule, it is most important to address the cause of a problem before taking immediate remedial action. More often than not, if the cause is not identified and addressed, the problem persists and the symptoms recur. As with all buildings, it is best to be proactive in the preservation of log structures and to perform preventive maintenance tasks as often as necessary. A structure should be inspected annually, with a checklist in-hand, and anything and everything should be documented. In other words, you cannot take too many pictures!
Issues Typical to Log Structures
Due to the poor nature of the design, there are numerous problems that are typical to the log building type. Examples of poor design features are the exposed log crowns that typically project past the roof eaves, rafters and purlins projecting past roof eaves, lack of gutters causing detrimental splash back because water isn’t dealt with properly at ground level, site drainage towards the buildings, no foundations, no airflow beneath the buildings, and others. Moisture, climate, pests, poor building details and human impact are the major common forces behind persistent problems.
Excessive moisture on a building can cause fungal decay, shrinkage, erosion, expansion and contraction, as well as capillary action. Each of these issues then cause different problems within the logs that require unique treatment methods based on their severity and location.
Rafters and purlins are commonly deteriorated by roof runoff, or as a result of holding snow or ice which wets the ends of the members and causes deterioration at the top of the log and often up the center as well. Moisture on log ends moves into the notches and, though it generally stops there, water can continue further into the log, creating greater degradation at the center of the log.
Wind, ultraviolet rays and fungal decay are problems affected by the climate that will also cause deterioration of logs over time and will add to the build-up of organic matter in areas of deterioration and check cracks. These checks are generally not an issue, unless the checks are located on the top side of the log, which allows water to the heartwood at the center of the log and leads to rotting from the inside out. Additionally, when debris is caught in the checks, moisture can be trapped, accelerating deterioration.
Pests (insects, rodents, bats, birds, etc.) are another problem that can contribute to the deterioration of log structures. The type of pests that target a log structure depends on the building’s location. For example, termites will move up wood where it touches the ground, while ants typically only eat already rotted wood.
Poor building details--including exposed log crowns (Image 5), rafters and purlins, poor site drainage and layout, logs at grade with inadequate an or absent foundation, and aggressive vegetation can cause problems with roof runoff and splash back, ponding water, lack of ventilation, ice and snow build-up, deteriorating chinking and daubing, settlement, and can lead to biological growth on the building or even within the logs. Each of these problems, along with inattention and ignorance of proper maintenance or treatment methods, contribute to the deterioration of log buildings.
Thankfully, there are several very simple solutions to the causes of some of the more common problems:
- Provide wood preservative as a means to protect wood from fungus, termites and other wood-decomposing organisms that find their way into cracks or deterioration pockets in the wood.
- Maintain a finish or coating on all surfaces. Wood finishes can be penetrating products (typically oil-based stains) or film-formers (often a water-based coating) that can also act as a water repellent.
- To help prevent biological growth/fungus on building surfaces, clean the surface of wall logs and clean the roof surface and edges, including between shingles.
- Ensure that the grade is 8” or more below the lowest wood element. In addition, it is critical that surface water drain away from the building to prevent puddling and saturated soil near the foundation.
- All branches should be trimmed at least 20 ft. away from building roofs and 5 ft. away from building walls.
- Properly provide regularly scheduled maintenance on your log structure.
Once the cause of the problem has been addressed, it is appropriate to evaluate a proper treatment for the repairs. When dealing with logs there are several fairly typical approaches to treating problems. Dutchman or Butt repairs (splicing) can be used for partial replacement of log crowns, purlins or rafters; whereby new portions of logs are crafted from a log of the same diameter as the portion being replaced and connected to the existing log by mechanical means. Where capillary action has deteriorated the center of the log, such as in a rafter end, consolidants can be used to fill the center with a patch and a cap to cover the end. Deteriorated hollows in the existing log can also be filled with a consolidant. Severely deteriorated wall logs can be refaced by careful removal; replacement log faces should match the existing log in diameter and shape and should be connected with reinforcement and epoxy. Replacement of entire logs should always be a last resort unless detrimental to the life safety of the building.
Though hefty in stature, because of problems inherent in their design, log structures are actually quite delicate. Many of the character-defining features of a log structure are, unfortunately, also the quickest to deteriorate, particularly without proper maintenance. Annual inspections of your structure, followed by an appropriate--and continued--maintenance program will allow your log structure to live on for years to come.
Specific treatment methods and recommendations are not included in this blog post; for more detailed treatment methods and recommendations and a history of Old Faithful Inn, see:
- National Park Service Preservation Tech Notes, Exterior Woodwork, Number 3: Log Crown Repair and Selective Replacement Using Epoxy and Fiberglass Reinforcing Rebars
- National Park Service, Preservation Brief, #26: The Preservation and Repair of Historic Log Buildings
- American Wood Protection Association, AWPA
- Goodall, Harrison and Renee Friedman. Log Structures: Preservation and Problem-Solving. Nashville, Tennessee: The American Association for State and Local History, 1980.
- Reinhart, Karen W. Old Faithful Inn: Centennial of a Beloved Landmark. Yellowstone Science, Spring 2004.
- Additional photos of Old Faithful Inn and other Yellowstone National Park images can be found here.
Capillary action: The ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity.
Check, checking: A lengthwise separation of wood that usually extends across the rings of annual growth.
Chink area: The space between the logs on a wall. Chinking: The process of filling the spaces between the logs on a wall and the filling itself. This is a three-part process consisting of an inner filling or blocking material, a middle layer of soft material (such as oakum), and an outer layer, which is the daubing material.
Daubing: The final layer of the chinking process.
Log crowns (Image 5): The end of the wall log, typically projects from the building corner and roof.
Rafters: Usually an inclined member that supports the roof. Can also be flat or horizontal.