Kwila is a tropical hardwood commonly used as a higher end decking timber throughout New Zealand. There is a general misconception that this timber requires no maintenance. That is simply not the case.
Unlike softwoods such as pine, Hardwoods do not go through any form of preservation treatment and therefore can deteriorate very quickly in New Zealand’s harsh climate.
Kwila will rot very quickly under plant pots or other garden furnishings where water is trapped during the winter months, and will dry out causing irreversible splintering during the hot summers.
When newly milled, kwila is a deep reddish brown colour however our strong UV quickly changes this into a drab grey if not properly protected. It is very difficult to distinguish between weathered kwila and weathered pine which makes the initial expense of kwila a bit of a waste. We often have customers say “but I like the grey look” to which we think “well why didn’t you just use pine then?”.
Just like pine, kwila (and any other hardwood for that matter) must be protected with a suitable oil based preservative or stain. The oils penetrate the timber providing nourishment and the colour tints provide UV protection. Water based stains do not contain the nourishing oils.
Products that product a shiny surface coating, not unlike a varnish, should be avoided as these break down under UV and are then almost impossible to fully remove.
Oil stains typically last 12-18 months after which they need to be recoated in order to continue their protection. In between coats a simple periodic wash down with a mild detergent will keep the timber looking clean without removing the precious oils.
During winter time, mildew and moss can form on shady areas. This can be treated with any one of the numerous slow release moss and mildew removers available at DIY stores.