How to choose the best wood
In looking at timber and how it should be used, I have been fortunate enough to use the notes prepared by David Hofmeyr of West Cape Joinery for a manual he wrote for the public and the joinery industry.
So for the next few months – with the odd break to look at your winter problems – we will look at timber and its uses in depth.
Let’s start with doors and windows.
Choice of timber
In SA a number of different woods are used to make doors and windows. The types of wood that can be used for internal joinery are vast, but not so many can be used externally to withstand our aggressive climate.
Some of the better woods for external use are listed below.
* Meranti is the most commonly used timber in joinery. The timber we import from Malaysia is known as “Standard and Better Grade” meranti or seraya. The better grades are exported to Europe, and a large number of logs are now going to China. As a result, the timber available here varies considerably in quality, density and colour. The darker, heavier timber tends to be more durable.
All wood swells when it absorbs moisture, and shrinks when it dries. This is particularly the case with meranti.
If the moisture content is above 20 percent, the conditions become conducive to fungal growth – or dry rot. Moisture is easily trapped behind paint and is often only discovered when it is too late.
If the timber is well oiled with a good timber preservative containing a fungicidal additive, meranti joinery can last the life of the building.
Meranti is not recommended for external joinery at the coast.
* Okoume resembles light red meranti in texture and properties, but is more uniform in colour. It is grown in Gabon, and it has usually been used for plywood. Okoume has not generally been used for external joinery, as it is not very durable.
It costs the same as meranti.
l African mahogany, a West African timber, consists of a number of sub-species that are sold under the French name of Acajou d’Afrique. The most desirable species for joinery is the Khaya Ivorensis, but it is difficult to obtain this timber without other sub-species being mixed in.
Acajou is an attractive red-brown wood and is denser and more durable than meranti. The grain is typically interlocked, sometimes straight, and is attractive when finished with a natural preservative. It is a good choice when a better wood is required that does not blow the budget.
Although the wood is reported to retain its shape well after seasoning and shows only small movement in use, it can warp when exposed to the sun, and should be used with caution for tall and slender doors or casements.
* Kiaat is commonly found in central and southern Africa, and is well known in SA. It is also known as “mukwa” or “bloedhout”. Most of the wood is dark brown, but there are flashes of light-coloured sapwood and red veins that provide an attractive contrast.
The wood is very durable. When properly sealed, kiaat has great stability and it undergoes very little change in response to weather changes. It is an excellent wood to use for external joinery in southern Africa at a moderate price.
* African Padauk is a cousin of kiaat. When first machined, the heartwood is bright orange, but it reacts to light, and darkens through an attractive deep red-brown to chocolate brown.
The wood is strong, durable and exceptionally stable and exhibits negligible movement after manufacture. It is an excellent choice for joinery as well as flooring, and can be used where underfloor heating is installed because of its dimensional stability.
* Iroko is an attractive wood from central and west Africa that has been widely used for joinery. When kept well oiled it is a rich golden-orange to brown, with an attractive grain. It has been used as a substitute for Burmese teak, and has acquired the nickname “poor man’s teak”.
Unfortunately, it is popular in Europe, and this has driven up its cost so that the premium one pays in SA for iroko joinery when compared to meranti is 60 to 80 percent.
l Afrormosia, a rare species of timber, is protected by CITES, and cannot be harvested without a special permit. This inflates its price, which is just as well as it would otherwise soon be extinct.
It is mid-brown in colour, with a straight and sometimes interlocking grain that finishes to a most attractive lustrous colour with a clear wood preservative. This timber is often substituted for Burmese teak.
Afrormosia is an ideal wood for external joinery for those who are willing to pay the premium in price for a product that will last as long as the building.
* Burmese teak is the Rolls Royce of joinery timbers. The wood is attractive, durable and stable, and even after 100 years or more the lovely fragrance of the oils in the wood are still evident when it is exposed. It has become expensive, and is not used very much except for the restoration of heritage buildings.
If money is no object, then this should be your timber of choice. - Weekend Argus