After planning the project execution starts
Here, both phases may overlap to a certain extent, but the planning, depending on the nature of the project, must be completed more than 60-80% in order to start the execution.
Starting with the execution too early may lead to unexpected significant additional costs and time delays, when planning is still on flow and no final design documents are available.
At the start of execution it should be payed attention in particular that, for example, the dimensions of vessels and containers are known and finalized (this implies that they are ordered and the fabrication drawings were present!). And that these dimensions are included into 3D models and isometrics.
If this is not the case, massive modifications to prefabricated parts such as structural steel and pipes must be expected under certain circumstances.
A delayed start of execution does not have the consequence of a delayed completion - on the contrary, it can also be advantageous. For example, if at the time of the delayed execution all apparatuses, containers,
structural steel parts are already available and also a big part of the pipeline segments at the construction site, so this project can be completed faster than a project whose start of execution was in time but required massive modifications in the field.
However, in this case it is required that the building contractor has enough staff to occupy the site quickly.
That and much more needs to be regarded - the earlier in the project, the better the results!
If the pitcher starts to break, you will get difficulties in managing the rules, expenses and time delayes. And often only courageous measures will help to readjust the abondoned project again.
In both mentioned cases I can help you, because in the course of 20+ years of project experiences I have experienced and undergone all of it: the Good, the Bad and the Uggly !!