Dismantling of the old structure
Unscrew the hinges, remove the leaves, strip the joints. Clear the jamb with the crowbar, the plaster of the frame and the studs. If it is a screwing system, it will have to be segmented with a hacksaw. Release the frame: unscrew it if it is a metal frame; a wooden frame must be sawn at the upright, while the intermediate upright must be extracted with a lever.
Preparations for installing the window
Determine the location of the window: a frame installed on a hollow wall must completely fill the gap between the two partitions; on a solid wall, it will have to adapt to the internal surface. Evaluate the dimensions of the channel to be dug: the width of the notch must leave part of the frame up to date and take account of the support and the material of which the wall is made. Dig the rebate; check with square and plumb to optimize the horizontality of the support before cleaning.
The hinges must be placed in holes drilled with a chisel and ground after marking. Dust properly and then put putty on the frame and the support. Place corners to space the chassis wall. Position the window and hold it with wooden pegs on each side of the rails. Check that everything is perpendicular and that the leaves open without hindrance. To consolidate the sealing lugs, use a specific mortar. Make the necessary holes to screw the frame. Once it is stowed, seal the voids by injecting foam which must be leveled off once hardened and hidden with plaster.