Datums
Objectives
- Understand what datums are inside Revit models and families.
- Be able to start a project from the beginningand create all datums (levels and grids) with confidence.
- Be sure they are carefully placed because all other elements will depend on them.
Prerequisites
- User has basic skills in BIM modelling with Revit Software, and understands the language used.
- User has notions about the data structure in models.
- User has basic notions of parametrization.
Description
Datum objects are the abstract skeleton of levels, grids and reference planes that control the geometry of a project. This guideline explains how to create and manage these 3 types of Revit objects.
Datums are Revit elements that fit the project. They are used as references while modelling such as levels, grids or reference planes.
They are finite representations of infinite planes (vertical-grids, horizontal-levels, sloped-ref planes) that are shown as lines. They are not model elements neither annotation ones. We can say that they are a special category that are represented as annotation elements, but they do not depend from a view as the rest of them.
They should be defined at the beginning of the project as far as you can not create any plan view if you don't have the levels placed.
Levels
They serve to contextualize the model, Revit uses them to place many elements such as walls, floors, furniture...
Create
They are created in a section or elevation view.
They are always straight and horizontal. If you need any sloped reference, you should use reference planes.
They are defined by a name and an elevation.
If you create them with the Level tool, it will generate a plan view in the project browser. However, if you use the copy or array tool, you should create their plan views later. (Sometimes, in multi store building, the quickest way is to create them with an array).
If any level has already a plan view created, to create a new one it is necessary uncheck the bottom box.
Properties
Instance
Elevation: elevation level height. It is recommended to define the level height as 0.0m to the most characteristic project level (i.e. Ground floor)
Computation Height: the distance above the level that is used to calculate the perimeter of a room, area, and volume.
Scope Box: the Levels can be circ*mscribed to a Scope Box. It is useful for controlling the graphics, the levels ends will always be adjusted to the limits of the Scope Box.
Symbol colour: if the symbol is blue, it means that it has a horizontal view associated.
Type
Elevation base: If it is set as the Project base Point, the level elevation will be displayed according to the origin 0,0 Revit. If it is set as the Survey Point the level will be displayed according to the defined relative coordinates.
Line weight, colour and pattern defines the line graphics.
Symbol: Select the family for the end symbol of the Level. You can edit this family from the project browser.
Symbols at ends: They said if we see symbols on the ends by default or not.
Types
As other Revit elements several types can be created. It is useful when we have structural and architectural levels (they are quite close and it can be a mess.)
Using two types it is possible to difference their aspect, as we can see in the attached images.
It is possible to modify their visibility in specific views thanks to the filters as well.
Graphics
When we select a level we can see a “3D” text written. It means that it is the limit of the plane in the model. We can move it using the blue circle. If there is a blue line connecting all levels, when we move one of them, the other ones will follow it. However, if we would like to move just one, the lock should be opened.
When you need to move a level just in a specific view, but not in the entire model (that will affect to all views) the text should be “2D”. It is necessary sometimes when views are too big for the sheet and you need to resize the levels symbols in some of them.
It is possible also broke the horizontal line and customize the angled shape of the extreme. If the box is empty, the level name will not appear:
Propagate extends: This tool will apply the same 2D level configuration to other selected similar views.
Symbol graphic
Other Level heads can be customized by editing the family. It is important to check the subcategory of the line, to modify it in the project if necessary (Object styles).
Best Practices
Clarify the general criteria for levels
Decide if there will be different levels for finish floor level and structural elements, in which models they will be created or copy/monitored, etc. The most important thing is to avoid any user to create their own levels regardless of the rest, and that the model ends up having a large number of unnecessary levels.
Avoid replace levels with gaps: when you have items that need to be associated to a level of a link, it is better to copy/monitor that level than associate them to an own level with an offset. So get that if the level change, the elements move with the level, and if we gave a gap with respect to another level the elements would not move.
Use of level types: Revit offers us the possibility of creating different types of level. This can be useful to create such different levels of structure, architecture...They can also be useful when it comes to filtering levels or hide them. You can modify the appearance of the different types, its color, weight, etc, to make them easier to identify.
Naming
The project browser is alphabetically sorted, that’s why we use the number, to have them organized from top to bottom (i.e 00_Basem*nt02, 01_Basem*nt01, 02_GroundFloor…. It is also important difference between STR and ARC levels by using the discipline code or a suffix like FFL(Finished Floor Level) and CL(Concrete Level) If there is a mezzanine associated to a main level, it is useful name it as Level01’ to avoid any confusion.
Revit Level | Volume/ScopeBox | Discipline | Number | Elevation | Description |
STR_00_Level01 | T2M | STR | 01 | 7500 | Level01 |
Copy/monitor
The advantage offered by this system is that we can work with the levels by linking elements to them because they will be in the model, and also if they change in the linked model we will get a warning that they have been modified. When that happens we will see what has been modifying, and we will decide if we accept the modification or not.
Grids
In a project where there is structure is absolutely necessary to first model the main Grids.
Grid lines are finite planes. You can drag their extents in elevation views so that they do not intersect level lines. This allows you to determine whether grid lines appear in each new plan view that you create for a project.
Create
The Grids can be straight lines, arcs or multi-segmented.
They interact through the dimensions, it is worth remembering the use of the EQ button that appears in dimensions to match segments that are equidistant.
They are defined by a custom name. When we create a grid (i.e 1,2,3…) and we delete one of them, Revit remember the last name (although it has been deleted) and keep going with the sequence. It is important to rename this last grid to have the proper names and avoid rewrite all of them after finishing the grid drawing process.
It is appropriate to pin them to avoid any unconscientious movement that can affect dramatically to the project.
Properties
Instance
Scope Box: The grids can be circ*mscribed to a Scope Box. It is useful for controlling the graphics, the grids 2D limits will be always adjusted to the limits of the Scope Box.
Type
This properties are quite similar to the Level’s ones. You can choose the Grid head symbol and customize it family. Is it possible too to modify the segment color, pattern and weight. Which is different from levels is that you can choose different line type for the center and both sides.
Non-Plan View Symbol: You can choose if the grid head symbol will appear in the views that are not floor plan. And in which position (top, bottom, both, none) they will be shown.
Types
The same as levels.
In this case it can be useful if there are various buildings with different structure, or maybe if there are different structural systems that we should distinguish them visually.
Graphics
It works exactly the same as levels with the 3D property to change their representation in ALL views (in the model) and 2D option to modify their appearance just in this view.
Propagate extends: the same as levels
Best practices
Use types for managing grids with different intentions.
Naming: Use short names as A,B,C,1,2,3… because they will be used as reference position of columns.
Copy/monitor
Same as levels.
Reference planes
Use the Reference Plane tool to draw reference planes to use as a guideline in your design.
A typical case for Reference plans is to mark the axis of symmetry of the project (if any), if it is not necessary to print them, with a Reference Plane correctly named.
They are useful as:
- Work Plane (which can be displayed in 3D)
- Sloped plane to "host" elements. (i.e sloped roof to host the beams)
- To cut elements.
Create
They are created in a section plan or elevation view.
They are always straight. Arch and other shapes are not allowed.
They should be correctly named. If they are not named you can not use them as hosts.
Properties
They are the same as grids: ScopeBox and Name.
You can not edit the type neither create any new.
Graphics
Its visibility on the visibility/graphics menu cannot be changed. You are only allowed to change it in the object styles menu that affect the entire project and not just this specific view.
In Revit 2017 you can add a subcategory to a reference plane to control visibility and graphics settings.
Best practices
Naming: When different disciplines as STR and ARC are involved in the project, it is recommended to name the planes with the discipline code as prefix. It will avoid misunderstandings and further conflicts.
Tips & Tricks
If there is any CAD as a reference, it is very important NOT to use pick line tool to create these elements. They are enough relevant in the project to have a minimum offset or mistake in order for them to be straight.
Generally, the symbols that the default Revit template contains are a bit harsh. It is recommended to customize them and import them into the personal template with a proper dimension.
When you can not see some grids in a section, elevation or any other view, it is because they are not intersecting with the section, or they are not included in the far clip offset.
Conclusion
Creating Datums is the starting point of any model. Because of that is very important to place them accurately. The modelling will depend on them and they will be used as reference.
