What timber? How much?

Ruapehu Bulletin, Volume 8, Issue 370, 22 January 1991, Page 12

What timber? How much?

If like many New Zealanders you are planning to do some home renovations this summer you'll need an idea of what type of timber and how much you will require for the job.

How often have you unloaded the trailer and found you've ordered the wrong type of timber? The timber is too wet, the size, the finish and the profile are different, or you haven't got enough timber on hand to complete the job. A few simple checks can be used when ordering from your timber supplier. Timber species A range of imported and New Zealand grown timbers are available to the builder, each differing in its suitability for a particular end use. For example, Douglas Fir is suitable for framing because of its very good strength properties, but as it splinters very easily, it is not recommended for decking. Timber grade In addition to the timber species, the grade of the timber is important. Depending on defects such as knots, the grade of timber needs to be matched to the use the timber will be put. For example, timber framing in most instances needs to be graded to a number one framing grade, while dwangs between the studs need not be as strong and can be lower graded and less costly. Timber preservation Timbers have varying degrees of durability and resistance to attack the decay and insects. Most New Zealand grown pines have a very low natural durability and need to be treated with timber preservatives. Depending on where the timber will be used, a different level of treatment will be required. Most preservatives will need to be used for timber in contact with the ground, such as sawn fence posts or crib walling. House framing and flooring on the other hand, are protected from the weather and require less treatment. Timber surfaces Timber can be sold with a 'rough sawn' finish. Often construction timbers purchased direct from the sawmill will have a rough surface and may be still damp.

Most timber used for framing, joists, decking etc, will be planer 'gauged' where a smooth machined finish is given to the timber. Dry timber can be 'dressed' leaving a smooth finish. Timbers used for weatherboards, fascia, flooring and panelling can also be machine moulded to give a particular profile or pattern. Timber size Timber is sold by its length and by its cross section. timber is sold in standard lengths beginning at 1.8 metres and increasing by 300mm increments, i.e. 1.8m, 2.1m, 2.4m etc, up to 6metres. Timber is sold in standard dimensions, for example 100 x 50mm. The actual dimensions for the timber may differ depending on the level of moisture in the timber, and whether it has been machined. Dry dressed 100 x 50mm timber for example may actually be 90 x 45mm, It will however, still be referred to as 100 x 50mm. Moisture content Again, depending on where the timber is going to be used, the level of moisture in the timber is important to the builder. Although timber framing can be installed in a wet condition, local councils require that the timber be dried down to a certain level before putting on the internal lining. More demanding uses such as flooring and panelling have to be dried down to very low levels before installing the timber to prevent shrinkage and swelling. Timber standards have been designed for specifying the required grading, preservation, sizing, profiling, level of moisture content and suitability of timber for particular end uses. Before ordering your timber, refer to these standards. This information should be available through your local building inspector or timber supplier. More detailed information on timber use can be obtained from your nearest Ministry of Forestry office.