Wednesday, 23 August 2017

Scheduling Global Parameters in Revit

Revit is all about data and displaying or extracting that data.  So, you'd think that when a new Revit feature  is added, like Global Parameters, you should be able to schedule them?
Wrong!  You cannot directly schedule or tag Global Parameters in Revit.

However, I have devised a workaround (NB. this won't work on Revit 2016 R2):

Example 1 - Reporting Dimensions

In this example there are several sloping ceilings.  Each ceiling has a built-in property 'Height Offset From Level', which represents the height of the base of the ceiling slope.  This can easily be scheduled.  It is not so easy to schedule the height of the top of the ceiling slope - unless you use global parameters:

Step 1 - Reporting Dimensions

  • In a section view, add a dimension from the level to the top end of the sloping ceiling
  • Associate this to a global parameter
  • Make it a reporting parameter

  • Repeat this step for each sloping ceiling

Step 2 - Project Parameters

  •  Create a new instance project parameter called 'Ceiling Top Height'
    • Make it a length type
    • Apply it to the ceiling category
    • Give it a meaningful tooltip
  •  Each ceiling will now have that property, albeit blank


Step 3 - Associating Global parameters

The Project parameter properties of individual ceiling elements then need to be associated to the relevant global parameters (reporting dimensions):


  • This obviously means that one global parameter is required for each ceiling, which could become tedious for many elements - but this a workaround, after all.

Step 4 - Create the Schedule

A schedule can be created to display this information:
  • A ceiling schedule could be created, showing the built-in height parameters and the project parameter with associated global parameter

Example 2 - Area Calculations and WC Numbers

Step 1 - Global Parameters

Create your global parameters, with formulas as required.  In this example, global parameters are being used to calculate the number of toilets required for a community hall, where the statutory regulations require a certain number depending on the floor area of the hall:

  • There are two reporting parameter dimensions for room width and length.  
  • These are used to calculate a room area - this is an extra step to be taken because even though Revit gives us room areas automatically, we are not able to associate areas as reporting parameters, so we can't use the system Area property (except as a check on the calculation)
  • There is a user defined "Area per WC" - which is set as 1 WC required per every 30 square metres of the hall area.  This value can be changed later.
  • To establish the number of required WCs, a simple calculation is done:
    Hall Area / Area per WC
    This is an integer parameter so it always gives a whole number;  however, you could make the formula a bit more complicated so it always rounds up to the next integer
  • There is another check formula that sets the minimum number of WCs to be 2 - this is partly because arrays will only accept 2 as a minimum.  There is an 'array workaround' if the minimum really needs to be 1, but that is not shown here.

Step 2 - Project Parameters

The trick for being able to schedule and tag global parameters is again to use an intermediary - namely Project Parameters:
  • As many project parameters are created as you need for scheduling/tagging global parameters
  • They are defined for the categories to be scheduled - in this example it will be for both rooms and generic categories
  • 'Area Calculated' is added to the room category so that it can be scheduled and tagged
  • It must be a shared parameter for tagging;  if you want to apply it to just one category and only schedule (not tag), you might get away with it not being shared;  for multiple category schedules it needs to be a shared parameter.

  •  'WC Numbers' is an integer parameter added to both the room and generic categories - for rooms it is just for schedules/tags;  for generic categories it is being used to drive the model - number of WCs in the array

Step 3 - Associating Global parameters

The Project parameter properties of individual elements then need to be associated to the relevant global parameters:
  • The room element for the hall has its 'Area Calculated' property associated to the 'AreaCalc' global parameter
  • Its 'WC Numbers' property is associated to the 'WCNumCalc' global parameter

  • The WC cubicle component has a family property for the 'Number of WC Cubicles', which is used to control the number in the array.  This is associated to the 'WCNumCalc' global parameter - so that when the hall area changes, the global parameters recalculate the number of WCs and push that change into the cubicle array component..
  • NB. It is not possible to associate a global parameter directly to an array number in the project environment, so the array has to be built into the family - another workaround.

Step 4 - Create the Schedule

Schedules can be created in a number of ways to display this information:
  • A room schedule could be created, which shows the contents of the room

  • A better way to achieve this is to create a multi-category schedule that includes one element in the required room (Hall) and also the WC cubicles in the other rooms
  • Room properties can then be added for each element - in particular the project parameters for the hall room
  • The one element in the room 'Hall' needs to be listed in order to display the associated global parameter values of the room (Calculated Area & Required WC numbers), even if we don't want to schedule that element itself. This is because a Revit multi-category schedule cannot contain rooms as one of the categories - only the room properties of other category elements.
  • In this example, the schedule needs to be filtered to restrict it to just show generic category elements (WCs) plus the category of the element in the hall (a door in this case, but it could be anything); and then further filtered to get only the relevant ones listing

  • The fields from Rooms and Count, can be renamed to indicate required and supplied WC numbers


These are only two specific examples of how global parameter data can be scheduled and displayed.  Of course it is unlikely to suit your exact requirements but it should demonstrate the principles to be applied to different situations.

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