Installing, sliding, folding and sliding sash windows:
The operation of sliding doors is very sensitive to the way in which they have been installed. A small variation from plumb or level, or a small drop of the lintel above, can prevent the doors from sliding freely or closing properly. This will be a constant source of irritation.
It is best to fit sliding doors into prepared openings and after the brickwork has had a good chance to set.
However, sliding doors can be built in successfully if the proper precautions are taken.
It is important to check the operation of the doors soon after the brickwork has been completed. It is better and cheaper to take out the door and refit it at this stage than when the owner is about to move in.
A helpful addition is to fit a compressible strip, such as “Compriband”, between the frame and the brickwork on the two sides and on the top. This helps to relieve any stress on the timber, and there is less chance of the door being deformed. In any event, a gap must be left between the head of the door and the lintel, and only caulked up much later.
Under no circumstances must the lintel or brickwork rest on the head of a sliding door. At the time of caulking, the frame head should be secured to the lintel at regular intervals to prevent it from dropping.
It is particularly important in the case of sliding doors to support the sill with regular (and firm) bricks, and to anchor the sill down before caulking between these bricks.
The comments made above about sliding doors, apply equally to sliding/folding doors.
The most important point is to ensure that the frame is installed level, plumb, square, with equal diagonals, and without a warp.
After installation, the door must be tested to make sure it operates smoothly, and that the gaps between doors and frame are uniform all around (usually 3mm to 5mm, depending on the wood species). The sill must be secured level, and prevented from bowing up. The head must be kept free from the lintel until deflection has taken place, and then secured at regular intervals to the lintel to prevent it from dropping.
Casement windows do not usually give a problem as a result of installation difficulties. But the same principles that apply to doorframes also apply to windows.
The traditional way to install vertical sliding sash windows is to build them in during the brickwork phase. They are secured by their “horns” built into the brickwork, and they do not usually need any other means of fixing. On no account should nails or anchors be fitted to the back of the “box”, as this will prevent the weights from sliding up and down, and the windows will not operate.
Some manufacturers provide DPC fitted to the sides, which needs to be folded out and built between the outer and inner brickwork skin. If not supplied by the window manufacturer, it needs to be fitted prior to installation.
It is best to staple an edge to the front edges of the window, leaving enough length to extend from the bottom to the top of the window.
Although sash windows are quite rigid in construction, the usual checks of level, plumb, square, diagonals, and warp should be done when the window is fitted, and again when the brickwork is completed.
Vertical sliding sash windows can also be fitted into prepared openings. Some favour leaving pockets for the horns, to be closed up later. This can lead to cracking, as a result of the mortar not filling the space between the bricks, or due to shrinkage, and is not recommended.
Blocks can be provided in the boxes at the top and bottom so that frame anchors can be screwed and plugged through the inner face of the windows in the corners.
The use of polyurethane foam is not recommended. The ply back to the “boxes” is too flexible, and would deform under the pressure of the foam. - Weekend Argus