How to Select and Specify Macrocarpa Timber
New Zealand Macrocarpa timber comes in a number of different grades, finishes & moisture content. When specifying macrocarpa three things need to be considered:
1. Grade - The quality can be one of clears, dressing, landscaping or boxing grade.
- Clears is a grade free from knots and defects, is available in most board sizes up to 300x50 although it is difficult to get in bigger sizes.
- Dressing is a grade with small tight knots and minor defects and is available dry in most sizes up to 300x50 and in green sawn or dressed in all sizes.
- Landscaping is a lower grade which has knots and defects that make it unsuitable for structural use unless a more rustic appearance is required, it comes in a range of sizes 150x50 to 300x100 or bigger. Is usually sold green sawn and used in structures out side.
- Boxing is low grade of board sizes 75x25 to 100x50, usually sold sawn, in small pkt lots at a low price.
2. Dry or Green
- Dry means the timber has been filleted and air dried generally for a six month minimum for 25mm board sizes and longer for timber over 50mm thick, up to 15 months for 100x100. This ensures the timber has shrunk and stabilised. It is difficult to kiln dry macrocarpa from green as it suffers from cell collapse, splitting and shrinkage around knots causing problems with dressing and machining. Larger sizes are not dryed, it is better that they dry in place.
- Green means the timber has recently been milled from the log and has not been dried. Is available in all sizes and finishes, especially in the larger sizes.
3. Sawn or Dressed
- Sawn means the timber has a finish showing the marks from the sawing process. It can be a circular sawn finish or a band sawn finish. Most of our larger sizes have a band sawn finish and this can be specified if required.
- Dressed means the board has passed through a planer and now has a smooth machined finish on all four sides ready for sanding. Timber can also be profiled or supplied with a combination of finishes.
Technical Details of Macrocarpa
|Density||485 kg\m3 at 12% moisture content (medium density softwood)|
from green to 12% moisture content
at 12% moisture content
|Modulus of Rupture||74 MPa|
|Modulus of Elasticity||7.9 GPa|