But what if BMP is escalated to being a requirement necessary to achieve BIM deliverables? That it is not just an office “CAD manual” but a description of the limits of your BIM deliverable. An antidote to the unlimited scope of work a BIM Execution Plan can trap the unwary player into.
If there is a hierarchy of categories (Revit has user defined subcategories), try and manage those as well.
Also insist naming be major – minor – subminor etc. so similar things list together; instead of Door Type, Frame Type, Glazing Type use Type Door, Type Frame, Type Glazing.
Next list the parameters needed to create your schedules, which, when you think about it, is just a list of schedule headings. This list forms the master list of parameters.
- Thicknesses: actual material thicknesses or a ‘zone’?
actual thickness mean dimensions are too precise (eg. 92 instead of 90);
zones reflect reality – there is always tolerance, but then do you;
– ‘fake’ a material thickness – which ones – structure or finish; or
– add ‘tolerance’ materials.
- Minimum size: what is the minimum size that will be modelled?
what is identifiable on a 1:100 or 1:50 drawing; or
actual size 50mm or 25mm;
- Type of things not modelled:
fixings (bolts, screws, fixing plates etc);
materials or objects smaller than (materials thinner than 5mm, pipes < 25mm OD);
controls (buttons, switches etc), hardware (handles, hinges, latches, hooks etc.);
certain elements (reinforcing bar, single wire runs, etc).
other’s work (ducts if you are an architect, plant room walls if you are an engineer).
If you are worried about the imprecision of it all, make general statements, like “model elements will generally not contain parts smaller than 25mm”.
UK’s Uniclass is more BIM friendly (according to them), but has many unfinished parts to it. The US’s Omniclass is not as well structured for BIM, nor complete. Revit had to add non-Omniclass numbers when they introduced the ability to assign a value to Revit elements. And just to confuse everyone Omniclass includes tables called Uniformat (which is what the Assembly parameter in Revit is assigned to).
- Categories are used consistently
- Parameters are logically named, and there are sufficient to do the tasks required, but no more.
- Model Construction limitations and practices are defined.
- Naming of all things is structured and human legible.
- Classification numbers are assigned, where convenient.
So what are you waiting for, start your BMP today.
I don’t claim to be the font of all BIM knowledge. I’d be keen to hear from anyone who knows of other important Best Modelling Practices I may have missed.