BC3 file: the details
A .bc3 file holds the full structure of an estimate: chapters, line items, the breakdown of each item into labor, materials and equipment, prices, descriptive text and quantity takeoffs. The usual takeoff and estimating programs in Spain read and write it, so a designer can hand over the estimate and the contractor can open it in their own tool without rewriting it.
It is also the format in which construction price databases are distributed. For construction management software it’s the natural entry point: from the project’s BC3 you can generate progress billings, compare subcontractor bids item by item and track actual cost against the estimate.