Fixing Timber Window Frames to Masonry
Window frames may be fixed in position by either building in during the main building process or fixed in at a later stage. The actual method used will depend on door/window construction, the material used and the availability of the windows at wall construction stage.
In the built in process, the bricklayer fixes the timber frames by building them in as the brickwork proceeds.
- When building in a window frame, the window sill is bedded level using mortar and the head is checked for level and packed up as required.
- Temporary struts are used to hold the window frames upright. Jambs should be plumbed from the face, using a plumb and strut the first using a spirit level. Another method is commonly known as sighting--stand to the side of the frame, close one eye, sight the edge of the plumbed jamb with the edge of the other and adjust until both jambs are parallel. Its always better to check wit the spirit plumb afterwards.
- As the brickwork proceeds, galvanised steel or stainless steel frame cramps should be screwed to the back of the jambs and build into brickwork. Three or four frame cramps should be evenly spaced up each jamb.
- The horns of the frames should be cut back for building in, rather than cut off, which helps to fix the frame in place. The cut ends should be treated with paint or preservative to reduce the possibility of timber rot.
Steel frame cramps provide good fixings, because they are screwed to the frame and bedded in mortar, and as they are not disturbed by hammering. The frame cramp rests on the last laid brick and the next brick above the ties is easily bedded.
Screw ties also provide good fixings, and are screwed to the frame, avoiding vibration from hammering. The slight difficulty is, that the brickwork has to be stopped one course below the required fixing to allow rotation of the loop when screwing in.