The question relates to timber of cross section 200mm x 250mm for a large outdoor architectural feature. It needs to stay straight, not split or warp, and to silver off without the need for staining and other maintenance.
The size of the beams and availability could be difficult. Indigenous timbers which might have the durability (beech, totara) are not likely to be available in big enough sizes or big enough quantities. The size also means the timber could not be dried and that makes stability a problem.
A good solution would be macrocarpa or Douglas-fir heartwood glulam as the lamination will overcome any problems with knots and it will be properly dried before it is glued.
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