Rimu

Description

The heartwood timber varies in colour from dark reddish to yellowish brown, with irregular streaks that give it its unique rich toning and attractive appearance. The sapwood is a uniform pale brown.

The heartwood and sapwood zones are separated by a drier intermediate band. This is a transition zone containing a progressively lower proportion of heartwood content as it moves further away from the centre of the tree.

The wood in this zone is a pale biscuit-brown colour, more even toned and slightly darker than the sapwood. Despite this transition, the timber from this zone is usually classed as sapwood because of its lower colouring distinction when dry.

Both heartwood and sapwood have a high moisture content in the freshly sawn state. Heartwood has between 90–130 percent moisture content, sapwood up to 140 percent, while the drier intermediate zone has around 60 percent.

Rimu timber has barely discernible growth rings, averaging 14 per centimetre. The heartwood is highly decorative with a close, even texture, and is harder than the sapwood and very stable.

Performance

Durability

Rimu has moderate durability, with the heartwood (Class 3) being more durable than the sapwood (Class 4).

The timber is not recommended for use as posts, or where it will come into direct contact with the ground.

A 50 x 50 mm heartwood stake will last in the ground for just 10–15 years.

Heartwood timbers can, however, be used in exterior situations for replacement cladding, window frames and exterior doors and jambs (such as in renovations to older homes), but should be replaced every 15–20 years.

The sapwood and intermediate zone wood is perishable and suitable only for indoor applications.

Rimu heartwood and sapwood can be used in interior situations for a variety of applications, without the need for treatment from decay.

Rimu sapwood in older buildings has been susceptible to borer attack, however, this can be treated fairly easily with fumigants or paint-on applications.

Mechanical Properties

Rimu has proven useful for both structural and decorative uses.

For 12 percent moisture content defect-free timber, the following specifications are average properties measured from just four studies of small specimens (20 x 20 mm cross sections). Please note these comparative measures of strength are “laboratory” values using standardised short lengths of clear timber. These will not be the same strength properties as structural lengths of timber.
For the properties of structural length timber please see the tables under the structural design section.

Rimu has excellent performance when used as a column, such as in furniture legs, with high compression strength. It also has excellent nail-holding strength.

The sapwood is less dimensionally stable than the heartwood, but when peeled or sliced into veneer and used in panelling, the sapwood has the attractiveness of even-toned rimu combined with the dimensional stability of the substrate.

This makes it exceptionally useful and yet affordable for large surface areas such as in cabinetry, door skins and interior panelling.

Machining

Rimu is an excellent finishing timber, it turns well, and allows a high-class finish.

For this reason, it has long been used for mouldings and trim, both in the natural and coated state.

It has excellent heat-resistant capacity and has therefore been suitable for mantlepieces and placemats.

The heartwood can be prone to splitting when nailed, and pre-drilling is advised to reduce this risk.

The timber is fairly soft and will mark easily.

Considerations

Rimu takes coatings well, using either high-gloss, satin, oils or paint. It is easily glued and stained.

Because some woodworkers are susceptible to dust irritation in the nose and throat when machining and sanding rimu, it is recommended that a mask is always worn when this type of work is being undertaken.

Applications

Rimu can be used for almost all interior finishing applications, as well as in smallgoods, such as giftware and kitchenware, because of its decorative virtues and similarity to kahikatea and birch in being free of taint (it was used traditionally in butter boxes).

In recent years, there has been a revival in popularity of recycled rimu for mouldings and trim in renovated buildings, and it remains a popular furniture timber. Rimu veneers are also popular for kitchen cabinetry and interior door skins.

Availability

There are still reasonable supplies of sapwood available in most sizes, but the availability of high-quality heartwood and coloured grades is diminishing rapidly.

The limited supply of rimu is in demand by furniture manufacturers. There will inevitably be substitution for rimu where manufacturers are unable to source sufficient and continuous supplies (some manufacturers are already replacing rimu with New Zealand beech).

There is likely to be increased pressure on supply and price in the future, but only to the extent that rimu prices remain competitive with other comparable timbers of similar quality and availability.

Rimu supplies from demolition yards are a good source of quality heartwood timber, and can be machined and reused as quality furniture, flooring and joinery.

Recycled flooring is, however, primarily characterised by nail holes or other defects, which can be featured as ‘rustic’ pieces.

For detailed information on vendors supplying rimu including their location in New Zealand and products supplied refer to the Suppliers Database or go to the NZ Farm Forestry Association Marketplace for availability.