By Roy Trembath All photos: Roy Trembath
It all began when I needed a workshop – somewhere to do my work and store my tools. Roy’s Garden Shed began as a project to build a 140m² carpentry workshop and parking garage for four vehicles at my property in Wilderness Heights, near George in the Garden Route.
Log building is my speciality, and I have taught log home building courses to thousands of people. Building material for log homes is cheap, strong, economical, environmentally sustainable, and easy to work with. A tree is at its lowest value when standing in the forest.
Any building project begins with a blank sheet of paper and a pencil. At the beginning, when I am designing the building, my thought process is simply what do I want to see when I come down my driveway?
Sourcing available materials
An important point to remember is that one needs to design according to what materials are readily available. For years I have habitually gathered a mental catalogue of suitable trees growing in the area, one particular stand of Eucalyptus saligna/ grandis growing nearby on the foothills of the local Outeniqua mountains had caught my eye. These trees were tall, straight, and perfect for log building. The biggest challenge was going to be accessibility. They were growing on the mountainside behind Wilderness Heights, and the old logging track had not been used for so many years that trees larger than 30cm diameter had grown in the middle of the road. I was told that in the distant past they had used oxen for log skidding on this track.
Next step: sourcing timber
The trees where originally planted about 100 years ago for honey production. Since then, they have self-seeded and invaded the surrounding indigenous forest, and today pose a risk to biodiversity.
After long conversations and several cups of coffee, the owner of the land agreed on a price to sell the timber, as he wanted to clear the alien vegetation from his property. I made an inventory of the trees, spent a couple of days in the forest, numbered, recorded the sizes, and estimated useable lengths.
An accurate scale model was built working from a detailed inventory list, a final design, and several sketches. The scale model helps to visualise the sequence of construction and how the structure fits together. It is almost like running a 3D simulation of the final construction project.
The fun begins when cutting down trees
I enjoy getting out into the forest, hands on, felling all the trees myself. I have one worker to help. We fell the trees, strip the bark, and treat them with homemade Borate solution. The logs are skidded down the mountain using a tractor and stacked at the roadside.
Moving them to site is easiest done by hiring a logging crane truck. It is essential to find a driver with a sense of adventure, since some of the logs are over 20m long, sometimes leaving 10m hanging over the back of the trailer. I guess it is needless to say that we did not use the highway.
The biggest log was 7m³, estimated weight somewhat over 7 tons (t). Crane trucks do not generally move logs of this size.
Once the logs were delivered, the construction started immediately. We did thorough preparation and were ready to start building as soon as the local Municipality approved the plans. While we were waiting for approval all the foundations were poured and allowed to settle.
Not rocket science, simply stacking timber
Once we started stacking the wall logs it took seven days for the building to reach roof height. I added one layer of logs per day. I like using the biggest logs that I can get my hands on, the thinking being that the bigger the logs, the less required to reach wall height, and the building goes up faster. Saying that, one can only use what is available, and some of my students have even used Black Wattle logs as small as 120mm diameter with great success – you just need more of them. The layers are pinned together with 12mm high tensile steel reinforcing bar which serve as oversized nails. The structure is simple, strong, and easy to build.
The ridgepole lifting team
Of course, one must put the biggest log at the highest point of the building – this is called the ridge pole. First, we raise support logs, which are bolted onto the walls using M20 threaded bar, then we lift the ridgepole on top.
This ridgepole is 20m long and more than one metre in diameter – this is where our 7t log ended up.
It is to be expected that lifting this would take some effort. However, with the correct rigging, it can easily be done by hand. This particular ridgepole was so heavy though, that I had to ask one of my students to assist me (my wife was not available to help that day). It took a couple of gin poles, two chain blocks and 18 minutes of lifting work but the sense of relief afterwards generally calls for a small celebration.
Installing the roof structure
At this stage we are ready to begin installing the roof structure. The roof structure on a log building is simple. There are no roof trusses. For rafters we use 300mm diameter poles which are pulled up onto the building and bolted together at the peak. Once they are bolted together, they can be slid along the ridgepole to achieve the correct spacing. These are spiked into the ridgepole and walls with 12mm reinforcing bar. Simple and sturdy. The fact that there are no roof trusses means that the entire roof cavity is available as usable loft space, which doubles the floor area of the building without adding anything to the cost of the foundations or roof.
During the planning stage I had cut and seasoned about 4 000 running metres of 28mm thick Saligna planks. I like to pin stack and air dry all the planks on site where they will be used. These would end up as 24mm tongue and grooved ceiling boards, effectively the same planks that most people use for flooring. The ceiling boards are painted and nailed on top of the rafters, which creates a clean finish inside with little effort.
Above the ceiling boards, furring strips and purlins are fastened to the rafters, insulation installed and then my all-time favourite leak proof concealed fix roof sheeting.
To finish the building, gable windows and doors where built. For gable window frames I use my own standard size square 150mm x 150mm Saligna beams, which are cheap and easy if you have your own log saw and a basic knowledge of chainsaw carpentry.
The final result
- Economical: Total cost R120 000
- Easy to build
- Environmentally sustainable: The trees will re-grow many times during the lifespan of the building
- Biodiversity: All timber is alien vegetation Eucalyptus Saligna / Grandis
- Carbon negative, this building consumed about 150m³ of round logs
- No milling loss: using round logs, we use 100% of the log, and minimal processing is needed.
- Quick to build: The project took 4.5months to construct with one labourer.
- Great insulation R value
- Long lifespan
- Materials readily available
- Environmentally friendly borate treatment
- Log buildings look cool.
- Building log homes is probably the most fun that you can have that is still legal.