German VOB Standard Calculation Rules for Roombook

Learn the rules used by the German VOB Standard to calculate surface area and material application.

The VOB requires a specified opening measurement system for creating the room surface quantities. Depending on which trade the quantities are calculated for, there are different calculation rules in regard to the subtraction of openings/subareas. Specify these tolerances in the Calculation Settings dialog.

For example, the VOB defines the following opening tolerances for specific trades and materials:

Masonry, concrete, and reinforced concrete works

• Openings minor/equal 2.5 m² are ignored

Carpentry, wood construction, upholstery, curtain walls, plumbing, roof cladding, and sealing

• Openings minor/equal 2.5 m² are ignored

Tiles and plates, screed, flooring, wooden planks, asphalt, parquet works

• Openings minor/equal 0.1 m² are ignored

Plaster and stucco, paint and varnish works

• Openings, recesses, niches minor/equal 2.5 m² are ignored
• Openings, recesses etc. in floors minor/equal 0.5 m² are ignored

Natural stone works

• Recesses, openings minor/equal 0.1 m² are ignored

These rules were defined to simplify the process of calculating quantities by hand. This is possible by ignoring smaller openings and/or applying basic methods for calculating complex building parts. Where Revit allows for more precise quantity calculation, user interaction is still required in some cases to make important allowances and exceptions.