A ‘clash’ is the result of two elements in your design taking up the same space. In Building Information Modeling (BIM), Clash Detection is the technique of identifying if -- and where or how -- two parts of the building (e.g., plumbing, walls, etc) are interfering with one another.
There are 3 types of clashes:
1. Hard Clash:
This is when two objects are interfering with one another, such as a plumbing running through a wall in the wrong way.
2. Soft Clash:
This is when an object does not have sufficient geometric tolerances in the design. For example, an HVAC system needs space to allow for maintenance workers to operate in to service the system. If the building design lacks that space, it will see a soft clash.
3. Workflow Clash:
While not an object clash, in BIM a workflow clash results from inconsistent or conflicting building information. For example, an HVAC maintenance schedule that does not align with the scheduled delivery of spare parts.