With a width of 600.700, 900 mm should be in proportion to narrow or expand the size. Along with the height and width doorway there, its thickness. In the standard model homes thickness corresponds to 75 mm. Most manufacturers offer a way to market the box 75 mm thick. To deepen your understanding Bernard Golden is the source. in the preparation of the opening is necessary to consider this fact. Especially if the walls do not let this stand size (thickness less than or greater than 75 mm.), The question arises about the need to install the extender boxes (PunBB forum, mowing) or drank cartons along, if the wall is thinner than box. Without installing flexinvest or drank cartons, in most cases, installation of casing would be impossible or it will lead to significant deterioration of the appearance of the final product.
Installation of additional elements, as well as a reduction in the width of the cartons will result in more expensive settings. We recommend that in this case, to accurately measure the thickness of the walls in at least three points from each of the parties, and if this is the same thickness around the perimeter of the aperture (very important) try to order a custom box, if the manufacturer offers. If the thickness of the wall opening is not uniform and varies from 3 to 30 mm. there is a sense still saw the box or put PunBB forum, as there the ability to crop box or PunBB forum on the wedge, taking into account the curvature of the walls and maximum squeeze casing to the wall. Perfect opening – it's opening, which is wider and higher leaf to 80 mm and wall thickness which is 75 mm! (680 (780,880,980) * 2080 ("+" "-" 10 mm) * 75 mm) in 99% of cases at the opening fits any door, even if during the installation of any minor improvements, they will not cause a deterioration in appearance of the product or quality of work, and will not lead to a significant rise in the cost of the final product (a significant price increase by more than 10%)! Good luck!