Frame depth
In window and door construction, frame depth refers to the depth of the frame structure required within the masonry. It is stated in millimetres and, on modern triple-glazed windows, is at least 70 millimetres, though often as much as 90 millimetres. Older windows usually have a shallow frame depth. When replacing windows, it is important to bear in mind that modern, multiple-glazed windows have a greater frame depth than the old ones being replaced.
