The cost of maintaining a timber weatherboard home is a big consideration when choosing a premium cladding like timber. I wanted to look at what the real savings look like over 15 years of maintenance.
There are a number of improved factors which allow Shou sugi ban (also called yakisugi) to significantly reduce the timber maintenance cycle. In Japan, they never maintain charred cladding, and it lasts decades. Before I get into how charring creates a low maintenance cycle, I thought it would be interesting to find out the reality of standard timber cladding maintenance.
Talk to the Professionals
Being a timber finish manufacturer, I have a better understanding of this topic than most, but I lacked the hands on understanding of timber stain performance in New Zealand.
Realising this, I called the experts who do the work every day, New Zealand painting professionals. Luckily we are in Covid lock down which meant everyone had a little more time to talk with me, and what they had to say was very interesting.
Frequency of staining:
Like all exterior products, time to reapply and cost is greatly affected by many variables. These variables add to your cost, the more time left between coats means more preparation and cleaning, will scaffolding be needed, and the number of coats desired by the home-owner.
For the purpose of this article, asked the professionals to give a conservative average. Assuming the staining is not left too long between coats, 1 coat is required and that the house is a single story dwelling.
I have found oil manufactures vary greatly on suggested reapplication rates, ranging from 3-5 years down to 1.5 - 2 years. The painters told me it's more like every 1.5 - 3 years, depending on aspect and location of the house. Below are the factors in order of impact that affect stain deterioration.
Factors that deteriorate stain:
UV exposure - Northern sunny sides will always fade faster due to UV breaking down the ink pigments in the stain.
Quality of stain - Don't skimp on your stain, cheap stains have less ink pigments and fade fast.
Local weather conditions - the wetter and windier, the more your timber looses its natural oils.
Bugs and fungi - shady, damp and southern sides are more prone to mildew and fungi, so staining is needed to prevent growth.
*New Zealand has naturally high UV levels compared with similar latitudes. For example, our peak UV levels can be 40 percent higher than peak UV levels in similar North American latitudes (McKenzie et al, 2006).18/10/2017
How Shou Sugi Ban reduces the effects of nature.
The primary factor for houses needing restraining every 2 years due to colour fading in UV. Shou sugi ban timber is covered in black charcoal, so it doesn't need ink pigments for colour, and it is 100% UV proof. UV will not change the colour of charcoal, so the timber cladding stays black. The timber substrate is protected from the wind, sun and rain by the charcoal layer keeping its oils longer. The intense charring process burns off carbohydrates in the outer cell structure of the timber, this removes the food source for bugs and fungi.
Improved factors from charring:
100% UV proof
Hydrophobic - Repeals water from the timber
Durability - Longer life span of the timber
Resistance - Reduces the food source for bugs and fungi
Cost of maintenance for timber cladding:
After talking with 4 different professional painters in Auckland, Hamilton and Tauranga, the average costs are the following for an average sized home with 130m2 standard timber cladding.
15 years maintenance costs - 130m2 of timber cladding:
$29 per square meter - Includes labour and materials.
$3770 every 2 years
$26,390 over 15 years.
Annualised cost of $2199
Cost of maintenance of shou sugi ban timber:
For the same house with 130m2 of timber cladding your maintenance cycle is 5-7 years, to be conservative we will calculate this with a 5-year reapplication of oil stain.
15 years maintenance costs - 130m2 of charred cladding:
Additional cost of a shou sugi ban finished timber is $55 per square meter.
$7150 - charred finish
$29 square meter - Include labour and materials
$3770 every 5 years.
18,460 over 15 years (includes original charring cost)
Annualised cost of $1230
A modest home could cost $26,390 in maintenance over 15 years, and the shou sugi ban charring reduces that cost over 50%. With over a 50% reduction in maintenance costs it easy to see that charring timber is not expensive in the long run, and you have a stunning unique cladding finish.