At ThermaDura we have developed a smart and efficient system which enables the builder to install our wooden windows and doors economically and to a high quality standard. On the inside of the timber window/door frame we machine a 10.5mm wide groove (4 sided). This multigroove can accommodate reveals, interior sills and even gibbboard.


spec sheet




In the ThermaDura system the internal reveals are a non structural part of the window. The window is fixed in into the frame opening without the reveals attached (using concealed fasteners). After the windows and doors are installed, the reveals can be slid into the multigroove on the inside of the window/door frame. The advantage is that the tongue and groove connection allows for variations in wall thickness. Another advantage is that the builder on site can install the windows/doors first and then order the reveals.

Internal reveals conceals the window fasteners. Reveals are fitted after the window installation.


The same multigroove system applies to internal timber sills. The sill is fitted after the installation of the window/door into the multigroove (with the internal reveals attached). The bottom rebate of the sill is designed for easy installation and to cover up the gibboard edge without the need of fixing additional scribers.

Internal sill in combination with internal reveals. Reveals and sill are fitted after the window installation.


In New Zealand it is still common practice to install windows flush with the external cladding of the building. In this case your window is fully exposed to the elements, but more importantly it creates a cold bridge between the outside and the inside of the building.
In most cases only a thin 20mm piece of timber (reveal) is all the insulation around the windows which creates considerable heat loss.
 At ThermaDura we offer external reveals to move the window back into the insulation layer of your home to ensure maximum energy efficiency.

Optional external reveals with hardwood sill. The external reveals and sills are supplied pre-cut.


Depending on the wallcladding or personal preference, the windows and doors can be supplied with solid hardwood sills or a flashing groove.

The flashing groove is preferable for some cladding systems and the most common option in Europe.

NatureLine timber window with bottom flashing profile

Aluminium weatherbar, with endcaps and seal


Typical for European-style timber windows is the weatherbar. At ThermaDura we offer two different designs. The low maintentance is the Aluminium weatherbar. The Aluminium weatherbar includes endcaps and seal and is more suitable for high wind zones.


Wood lovers decide for the timber weatherbar which is finished in the window colour.

Timber weatherbar

Timber window.jpg

Aluminium Cover Cap option

Another common detail for European-style timber windows is the additional aluminium cover cap. The cap extends the maintenance intervals and comes in the same colour as the aluminium weatherbar. We strongly recommend using this cover cap option, especially in very exposed installation situations.