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At ThermaDura we only use laminated timber for our joinery. There are many advantages for the use of laminated timber for the manufacture of windows, doors and conservatories.


  • Laminated timber does not warp and twist and does not tend to crack

  • Laminated timber is structurally stronger than solid timber

  • It is a sustainable way to achieve the highest timber quality


For our windows and doors we use quarter or semi-quarter sawn timber. The timber is free of knots and defects and the moisture content is 10-12%.  This reduces movement in the timber and is another quality aspect of our joinery. The glue used in between the laminates is D4 exterior glue (marine grade).



All timber species we offer are durable by nature and are characterized with a high density. In other words we only use hard timbers for the structural part of our conservatories. The advantage of using high density timber is that it is resistant to mechanical wear and tear and that applied coatings last longer. The hardness of the timber also makes it more difficult  for organisms to penetrate the timber.

After squaring the timber we machine the faces in a state of the art hydro-planer which replaces the traditional sanding. This way we achieve a maximum durability of the applied water based finish.


Siberian Larch


Siberian Larch grows in Siberia, Europe and North America (Canadian Larch). Larch is very rot resistance, and so it is especially valuable for weatherboards, decking, posts, poles, railroad sleepers, and mine props. The harsh climate of Siberia and north Canada results in a very hard and durable timber. The high density of the Siberian Larch of 0.64 g/cm3 is proof of this. The high density and tannin content make it difficult for the organisms that cause decay to penetrate our wood. Siberian Larch is durable without additional chemical treatment. Siberian Larch is the perfect timber for conservatories.



At ThermaDura we offer to manufacture our conservatory windows and doors in American Oak. This historically important timber is classified as class two durable (BS EN 350-2). Oak wood has a density of about 0.75 g/cm3. It is known for its great strength and hardness, and is very resistant to insect and fungal attack because of its high tannin content. It also has very pleasing grain markings, particularly when quarter sawn. American Oak is durable without chemical treatment. Oak is a great timber for conservatories.


Oak windows
Accoya windows

Accoya wood is a sustainable high performance timber. It is Class 1 durable (comparable or better than the durability of hardwoods such as Jarrah, Rosewood and Teak) so no further treatments are needed. Accoya wood is non-toxic and doesn’t leech harmful chemicals.

Accoya is FSC certified and is a home grown alternative for exterior joinery.



We also offer other timber options for our conservatories, orangeries, sunrooms, windows and doors. Western Red Cedar and is a popular timber option for the exterior of a conservatory. Macrocarpa can be used for the structural part of the conservatory (laminated) and for the exterior. Please inquire for more timber options.


Exterior joinery is exposed to harsh elements most of the time. Heavy rain, hail, and extreme heat conditions are common in New Zealand. When exteriors are exposed over time the difference between any old window and a quality window becomes apparent. Fairy tales are told:  people say that “Timber windows are not suitable for the harsh climate in Central Otago” - we disagree.

Here are some key characteristics of quality windows and doors:


  • Solid triple tenon mortise and tenon corner joints

  • D4 marine glue used for laminations

  • 4 layer laminated timber for dimensional stability

  • The use of kiln dried timber (slow drying process), MC10-12%

  • Defect free timber

  • The use of semi quarter sawn or quarter sawn timber

Timber is a natural material unlike PVC and Aluminium. Timber windows and doors stay dimensionally stable in order to fulfil their task. We have benefitted from centuries of European design and skill in engineering joinery; we use that knowledge wisely. Unfortunately in our fast modern times the need to take the special characteristics of timber into account is often replaced by time saving work processes. At ThermaDura we are joiners with a passion for timber and we stick to the traditional skills without cutting corners.

Native timber
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