Charred larch is the superstar of the exterior of Mackit Habitat. Richly textured, dark and mysterious, it is a robust cladding that doesn’t pretend to be anything other than what it is. Charring timber is an ancient Japanese technique called Shou Sugi Ban, which dates back to the 18th century. Similar techniques have been adopted around the world, often used in America and northern Europe (such as the below Villa Meijendel by VVKH Architects), but seldom seen in New Zealand.
One way to achieve the charred effect, is to use a gas blow torch. This creates a carbon layer on the exterior that preserves and emphasises the grain of the wood, protecting the timber underneath. The charring process prevents the timber from decaying, makes it weather and UV resistant, and also significantly extends its fire resistance. From a maintenance point of view, there is no regular painting or staining required, and you can rest assured that the timber won’t ‘cup’ or warp as dark painted or stained timbers are prone to. Siberian Larch is preferred, in comparison to other timbers, as it has a much higher natural durability.
Habitat uses charred larch on every wall that will be seen close up. For example, by any opening door and within the carport. This provides a rich texture and point of interest, when using the building on a daily basis. We chose vertical shiplap (overlapping) boards to amplify the height of the angular form. Timber weatherboards are usually between 18-20mm, whereas weatherboards that are burnt require at least 28mm. This allows for a sacrifice of the board to the char. Weatherboards can be bought pre-charred, in various finishes from a soft brown with copper tones through to a blistered black (as below). After seeing these samples, we decided the look we were going for was a heavy char. In order to have full control of the aesthetic, we decided we would char the boards ourselves.
Our beautiful Siberian Larch arrived earlier in the year from BBS Timbers in Whangarei. We made sure we ordered enough spare to try out the charring techqnique in order to nail down exactly what process we were going to use, to achieve the desired look. Using a blow torch, we began burning the bare timber, so that a 2-3mm layer was charred. After charring a few boards, we soon saw exactly how to achieve our desired aesthetic. We also really enjoyed the organic nature of the process. Every board would be unique depending on the exact movements of the hand applying the char, and how long the flame was applied.
It is important to ensure that the edge with the shiplap join (where the boards overlap) isn’t heavily charred – as this part is thinner than the board itself and burning it would affect its strength and structural integrity. We just ‘dusted’ the flame over this area, to darken the timber enough so that when the boards were overlapped on install there wouldn’t be a lighter line visible. Spraying the boards with water immediately after burning was the next step. This stops the char process and prevents any warping.
At this point, boards can be ‘brushed’ to create a smoother texture. However, as the reptilian like texture is our desired look, we didn’t want to lose this. In fact, we wanted to preserve this texture and prevent it from eroding over time. To do this, we needed oil. The larch doesn’t technically require oiling, but doing so has a number of benefits. Oil will create an even more durable, weatherproof finish that doesn’t easily rub off on clothing or hands. Oiling also ticks off the necessary task of coating and protecting the edges and shiplap joins of the boards. As can be seen in the left hand image below, oiling can darken the boards. We wanted to find a solution that would result in minimal alterations to the char.
After extensive research and testing into the oils available we decided on Tung oil. David Wood at Supreme Oils in Napier recommended their Haarlem Danish Oil, which is made up of Tung oil, vegetable turpentine, and drying agents. The drying agent is important to avoid permanently darkening the boards. David also suggested adding a mould inhibitor, for added longevity and protection. Our custom mixed oil will be sprayed directly onto the boards after they have been charred and cooled with water. A final coat will be applied to the exterior boards once they have been installed. We are also excited about featuring the larch in our entrance hallway and stairwell. It will provide a beautiful link to the exterior and add a rich textural dimension to the space.
Now that we know exactly how we want to char and finish the boards, we have begun the task of charring and installing lengths upon lengths of larch. We already have several projects in the design phase where we are specifying charred larch. Due to our valuable time spent experimenting and researching this unique technique, we feel confident in both the durability and aesthetic effect of the specification and process we have settled on.