BIM and bills of quantities
Every project of the office is a building information model in Archicad. The drawings, schedules and bills of quantities are produced from it, and the client receives the 3D model with all its data and a virtual walk through the building.
One model instead of separate drawings
From the concept design onwards, the building is built as a three-dimensional model. Every wall, slab, roof and stair in it carries its layers and materials: reinforced concrete, masonry, insulation, render, cladding, with thickness and area. Windows and doors have dimensions, an opening direction and the type of wall they sit in. Every room has an area, a perimeter and finishes for the floor, walls and ceiling.
Plans, sections and elevations are views of the same model. A change to one wall is reflected everywhere: in the drawings, in the schedules and in the quantities. The drawings of the individual disciplines therefore do not contradict each other, and the contractor receives documentation in which the numbers agree.
From the model to the bill of quantities
Quantities are not calculated by hand from the drawings. They are extracted from the model as schedules and go into a workbook with the bill of quantities, whose formulas are linked to the data from the model.
- 1
Schedules from the model
Components by layer with volume in m³ and area in m²; rooms with area, perimeter and finishing work on floor, walls and ceiling; a window and door schedule with dimensions, number and wall type; slabs, stairs, railings; surfaces and materials.
- 2
Bill of quantities for the architectural part
The types of work by section: earthworks, formwork, concrete, reinforcement, masonry, insulation, roofing, finishes, windows and doors. Each line has a unit of measure and a quantity taken from the schedules of the model.
- 3
Priced bill of quantities and summary
The same quantities with a column for the unit price, which the contractor fills in with their tender. The summary adds up the cost by section. Tenders from different contractors become comparable because they are based on the same quantities.
- 4
Schedules and a model for the client
A schedule of the facades and the windows and doors, a room schedule. The client receives the 3D model with all its data in BIMx format: it opens on a phone, tablet or computer, with a virtual walk through the building and measurement of every element.
What the client gains
- The quantities are taken from the model, not copied from drawings. Fewer discrepancies on site and fewer “unforeseen” works.
- Comparable tenders from contractors: all of them price the same quantities.
- When the design changes, the quantities are updated from the model rather than recalculated.
- A model that can be understood without training in reading drawings: the building can be seen from inside before construction begins.
Projects with a BIM model and bills of quantities
- Residential building with garages, block 645: window and door schedules and quantities from the model