My observation of the pic - you will not be able to show building as though it were a merged Excel cell. "1" would have to be on each row. Nor could you replicate that exactly in a report. Just saying in case it's important.
I don't see why the main form should be unbound if that's what was meant. Whatever the data in the lower part is, it likely needs to be associated with the information at the top of the form. It's not clear if the link between the subform (lower detail section) and the main form (Workers, Data [is that "date"?], shift) would be 'building' or something else.
With that setup it could be that user would want to navigate through main form records (different Worker/Data/Shift values) and each time the main form shows a new record, the related subform records show below.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.