Lead time
Lead time is the span between an approval or order and the point at which a component can be installed. It is often invisible in the schedule, because nothing happens on site during that period – yet it affects the dates.
The chain before installation
Several steps precede actual production, each with its own duration: issuing construction drawings, preparing shop drawings, incorporating feedback, approval – only then does manufacturing begin. For windows and external doors, production times in the order of eight weeks are common.
The starting point is decisive: components such as blinds or railings are measured on the structure as built. Production therefore starts at a point in the middle of the sequence, not at the beginning of the project – here too, around eight weeks is a common order of magnitude.
Drying times
The same applies to waiting periods on site. A screed has to dry before floor covering work. As a rule of thumb, around one week of drying is allowed per centimetre of thickness – roughly seven weeks for 65 millimetres. During that time no work takes place on the surface, yet the fit-out remains blocked.
What follows from this
Such periods belong in the schedule as tasks in their own right, not as an unspoken buffer. If they are not shown, a schedule looks sound without being so: installation is planned earlier than it can happen. In Menira they can be kept as separate bars with dependencies, so that a shift in the structural works carries through to installation.
The periods given are orders of magnitude from practice. The figures of the contractor concerned and the conditions of the specific project are what count.