Fitting a subframe between the wall aperture and the window frame ensures that the window apertures are perfectly square. This allows a perfect fit between the window and the wall aperture.
In a house or block of flats with a large number of windows, the subframe ensures the standardisation of all the wall apertures, saving time in window installation.
The subframe is universal and can be used for any kind of window – casement, sliding, dormer…
FENSTER ALWAYS recommends subframes
The use of subframes always serves to protect the window from scratches and marks: once the building work is finished the window is fitted directly on the subframe. In this way the window is not marked with mortar, as it does not have to be stuck directly to the masonry and it is not marked in the process of rendering the wall.
As well as the benefits mentioned, the use of subframes has other advantages:
• it improves waterproofing against leaks
• it makes it easier to inject polyurethane round the edge
• it makes it easier to fit interior joint covers
Concealing the subframe: the subframe forms part of the wall and is hidden with a joint cover that comes with the window and is used to mask the joint between the subframe and the wall.
Fitting: the subframe is fitted before the wall is rendered. The thickness of the rendering must be calculated. This is the distance the subframe has to stand proud, so that it will be flush with the wall once it has been rendered. The subframe is fitted by the bricklayer.
FENSTER manufactures and supplies made-to-measure galvanised iron subframes