Building Information Modeling for Construction

This is an introductory section on BIM. From the next section, you'll learn BIM modeling with several hands-on exercises.

In Autodesk® Revit® software, you create walls using the Wall tool to sketch lines indicating where walls should be placed. As you sketch these lines, 3D wall elements are created in the model and appear in other model views.

The characteristics of the walls created are determined by the properties of the wall type that you have selected. You can specify the materials and structure of the walls being placed and wall height, and many other physical properties.

As you place or reposition walls in the building model, Revit software automatically joins the walls that intersect.

Walls are a type of system family that are predefined and live inside Revit project files (*.RVT) or project templates (*.RTE). The Transfer Project Standards command located in the Manage tab > Settings panel provides the ability to copy wall types from one project to another.

Review Questions

If a wall is connected to other walls, how will moving one affect the others?

Moving a wall will typically affect other walls to which it is joined. The other walls will stretch or shrink from trying to maintain the connection. If two walls have been constrained using a locked dimension, then movements to one wall will be mirrored in the second wall to maintain the distance specified in the constraint.

What methods can you use to resize a wall?

You can select a wall and then drag on the blue dots that appear at its ends to stretch or reduce the length of a wall. You can also enter a new value into the temporary dimension that appears when a wall is selected. If you want to extend a wall to meet another wall, the trim tool offers an easy way to quickly and precisely join two walls.

In Autodesk® Revit® software, doors are hosted by wall elements.  You create a door by using the Door tool to choose a door component and then place it in a wall that has already been modeled.

Similarly, windows are also hosted by wall elements. So the procedure for placing window components is similar to doors. You use the Window tool to choose a  window component and then place it in a wall element.

The characteristics of the doors and windows placed are determined by the properties of the door and window types that you have selected. You can specify the features, sizes, and materials by selecting different types as you place them. You can also easily change the properties of a  door or window by selecting it and choosing a new type.

Doors and Windows are a type of loadable family that is created outside of Revit project files and are loaded into projects when needed and have a *.RFA suffix. The Load Family command located in the Insert tab > Load from Library panel provides the ability to import library components into any project.

Review Questions

What do the temporary dimensions for a door or window element typically show

By default, the temporary dimensions show the distance between the center of the door or window to the nearest adjacent wall or the nearest door or window. You can change the temporary dimension preferences for a project to show the distance to the edges of the door or window (rather than the center).

How can you indicate the hinge side and the flip of a door as you are placing it? After it has been placed?

As you place new doors, you can indicate the direction that the door will swing into by hovering the cursor near the face of the wall on the interior side of the door. The hinge side of a door can be changed by pressing the space bar.

After a door is placed, you can select a door and small blue arrows appear that enable you to quickly change the flip orientation and hinge side.

When you place doors or windows in 3D views, how is the level associated with them determined?

When you place doors or windows in 3D views, Revit tries to determine the appropriate level based on the closest level below the sill of the door or window. Often, this is a good

All walls placed in a building model have a wall type associated with them. The wall type includes a definition of the layers and materials that determine the thickness of the wall, so choosing the correct type for every wall is very important for creating accurate building- models.

As you place new walls in your model, Autodesk® Revit® software automatically chooses the same type as the last wall created. You can accept this type or choose a different wall type using the Type Selector. You can also change the wall type after walls have been placed, but it is typically more efficient and better practice to choose the proper wall type as you place new walls.

You can create new wall types to model materials and wall assemblies that are needed for your design. And you can specify settings that determine the height of the top and bottom of the wall in the Properties palette.

Review Questions

How is the total thickness of a wall type computed?

The total wall thickness is determined by adding thickness to each of the different layers that make up the wall assembly.

How can changing a wall’s type affect the clear space between adjacent walls?

Changing a wall’s type typically changes the wall thickness, and this can change the space available between adjacent walls. Where the thickness will be added depends on the location line setting of the wall.

In a typical residence, what locations are most critically affected by the wall thickness?

Narrow hallways, closets, bathrooms, or anywhere where the space provided is close to the minimum clearances required.

In Revit, doors, windows, and wall openings are modeled as components that are hosted by walls. You place these elements by opening the Door tool, Window tool, or Wall Opening tool and then placing the component in a wall that has already been modeled.

While they are similar in many ways, the specific pieces contained in each type of component differ slightly because they include unique parts needed to perform their architectural functions:

• Door components cut an opening in a wall, which is filled by a door frame and one or more swinging, sliding, or folding door panels. Many door types also include interior and exterior trim.

• Window components cut an opening in a wall, which is filled by a window frame and one or more swinging or sliding sash panels. Many window types also include interior and exterior trim.

• Wall openings cut an opening in a wall but include no panels or other parts to fill the openings. Wall opening components are also available in the Revit Library to create nonrectangular shapes, and some components include the trim.

You can change the sizes of doors and windows by choosing different types in the Type Selector or duplicating an existing type and changing its dimension properties to create a new size.

Doors and windows can be placed individually, or you can use arrays to quickly place many components using even spacing. All of the elements in the array will be identical to the first and be spaced evenly along the length of the array.

After placing a door, window, or opening, you can adjust its:

• Horizontal placement—by dragging the element along the wall or adjusting the temporary dimensions to place it precisely.

• Vertical placement—by adjusting the Header or Sill height properties.

• Orientation—by selecting the element and clicking its control arrows to flip the exterior and interior sides.

• Hinge side (for doors only) and swing—by selecting the element and clicking its control arrows to change the location of the hinge and the direction that the panels swing.

Review Questions

Do the doors and windows move with the walls?

Doors and windows will automatically move when their hosting wall moves.

They can also move within a wall if constraints have been set up that link their position to other objects (for example, intersecting walls or nearby doors or windows).

Windows do not change location if the wall length or height is resized.

Do doors and windows automatically adapt to the thickness of the host wall?

Yes. The elements (frames, jambs, sills, and so forth) of the door and window components typically resize themselves based on the thickness of the hosting wall.

What happens if the boundary of the door or window exceeds the extent of the wall?

Generally, Revit will allow you to place doors and windows as long as the placement point―typically at the center of the window―is within a wall. If a wall is resized such that the placement point falls outside the new boundary of the wall, Revit will report an error saying that it cannot cut the wall opening and will remove the window.

Can you place a door at a height above or below the associated floor level?

Most doors offer a sill height instance property that enables you to specify an offset above or below a floor level.

You can edit the grid layout of existing curtain walls—adding, removing, or moving entire grids or selected segments—using the Curtain Grid tool.

With the Curtain Grid tool selected, you hover the cursor over the horizontal or vertical edges of a curtain panel, and Revit suggests potential grid locations that would divide it into even increments (for example, halves or thirds). You can also align curtain grids to other elements in your model by snapping to faces, reference planes, or levels.

When adding curtain grids to a wall, you can use placement options to:

• Add gridlines across all segments (the entire face).

• Add gridlines to one segment (a single panel).

• Add gridlines across all segments except ones that you pick to exclude.

Use the Mullion tool to place mullions on any grid line segment, on entire grid lines, or on all of the curtain wall’s grid lines and boundaries.

To make editing curtain grids and mullions easier, choose an elevation or 3D view that displays the horizontal and vertical grid layout.

Review Questions

Would it be easier to start by specifying a regular pattern in the curtain wall’s type properties, then modify it? Or would it be better to manually subdivide the wall by adding curtain grids individually?

If a pattern is simple, or it is to be repeated on multiple walls, then it would be easier to specify a regular pattern in the type properties. If only minor adjustments to the pattern are going to be made, then assigning a regular pattern may again prove to be helpful.

However, if each wall is extremely different, or the desired pattern is extremely complex, it may be easier to start from scratch instead of with a predefined pattern.

What types of patterns cannot be made using the layout options in the curtain wall type properties?

Vertical and horizontal grid lines can be placed at angles, offset, added, or removed, however, there is no option to create circular or curved grid lines.

How do you change the mullion properties (for example, the profile of the material) for a curtain wall type?

If the mullions are placed using the curtain wall’s type properties, then the mullion properties cannot be changed. We are only able to select a new, existing type within the curtain wall’s type properties.

If mullions are placed separately, they can be selected, changed, duplicated, and altered just like most other components in Revit.

Modeling an elevator in the Revit software requires several steps:

• Placing an elevator component

• Creating a vertical shaft to cut openings in floors and ceilings

• Adding walls around the elevator shaft

• Cutting openings in the shaft walls for the doors on each floor

If an elevator component is not included in your model, you can load one from an external library.

The Shaft Opening tool is especially useful for modeling elevators because it can cut a vertical opening through many floors, ceilings, and roofs. When you move or modify the boundary of a shaft opening, the changes are automatically updated on every level.

Review Questions

What are the advantages and disadvantages of creating floor openings with shaft opening elements versus editing the floor boundary?

By using the shaft opening tool, Revit automatically creates an opening extending through multiple surfaces. This is convenient when multiple boundaries must be edited because it eliminates the need to do each one separately.

The shaft tool creates problems when different shapes need to be created or when a different floor must extend into the shaft region. If part of a new floor or roof passes through a shaft region, it will not be displayed.

Why are stairs and elevators typically located very close to each other?

Both stairs and elevators are essential circulation elements and they must be easily located. If the elevators are non-operational and in cases of emergency, the stairs should be easy to access from the elevator location.

It is also common to place elevators next to stairways since they both require continuous vertical shafts.

When you create a new project, the Revit software creates four elevation views named North, East, South, and West. These names describe the orientation of the elevation view relative to the project north.

As you progress with your design and modeling, you will typically need to create additional elevation views and section views to focus on specific aspects of the project. You do this by:

• Using the Elevation tool to place an elevation tag that establishes the location and direction of the new elevation views.

• Using the Section tool to place a section line that determines the location of the cut plane and direction of the new section view.

• Duplicating an existing elevation or section view.

Like plan view, you can set visibility graphics overrides and adjust the view properties to set the crop boundaries, view scale, level of detail, and visibility of model elements.

Review Questions

What types of information are typically displayed in:

• Exterior elevation views?

• Interior elevation views?

• Building sections?

Exterior elevation views are useful for showing the architectural details and materials of the building facade and are often used to illustrate the exterior architectural appearance and features.

Interior elevation views are useful for showing the details of elements placed on interior walls, such as moldings, cabinetry, and fixtures.

Building sections are typically used to explain the vertical relationships between building elements and their connection details. They are also useful for displaying the details of vertical shafts and circulation elements, such as stair wells and elevators.

Should you create interior elevations for every room? What features of a room are best illustrated using interior elevations?

Interior elevations are typically not needed unless it is necessary to display a specific aspect of the design that cannot be explained well in a plan view. These features often include moldings, cabinetry, fixtures, appliances, and other interior details where the placement height is best explained in a vertical view.

What are the key differences between elevation and section views?

Elevation and section views are similar in many ways. The key difference typically is that elevations display an external projection of the elements that appear in the view, where sections are used to display a cut through the key elements.

What happens to the accuracy of objects that appear at the edges as you expand a perspective view’s crop region?

When expanding the crop region of a perspective view, the objects near the edges appear to be stretched out. To prevent this, it is important for the focus of the image to be located in the center of the image.

If you want to include a broader view of your model in a perspective view, how should you change the camera placement?

If the view has already been created, you can use the AutodeskSteeringWheels widget walk option to back up and see a broader view. You can also show the camera in a plan view, and then move it farther away from the target object.

Can you use a section box to cut away parts of a perspective view?

Yes. In a 3D perspective view, the section box can be displayed and its edges can be moved in much the same way as in the default 3D view.

You can create two types of 3D views in Revit:

• Default 3D views, which are orthogonal projections of the building model elements. In these views, the appearance of the model elements is not affected by their distance from your viewpoint. Orthogonal views are used when accurately representing the size of objects is important. They can depict views from the ground level, but they are typically used to present bird’s-eye views.

• Perspective views, which use a camera metaphor to create a perspective projection. In these views, the appearance of the model elements is affected by distance. Objects that are near the viewpoint appear larger, while objects in the distance appear smaller. Perspective views are used when having a realistic understanding of how the design will be perceived by nearby viewers is important. They are often used to create interior or exterior renderings.

You create new 3D views in three ways:

• Using the 3D View tool (which appears on the View tab in the ribbon panel) and choosing the Default 3D View option. If this view has already been created, it will be opened instead.

• Duplicating the Default 3D View, which appears as {3D} in the Project Browser. The view properties and settings will be copied and used to create a new view, which will appear in the 3D View section of the Project Browser.

• Using the 3D View tool and choosing the Camera option, which allows you t0 specify the location and elevation of a camera object and a target for the camera view.

You can also add section boxes to your 3D views to cut away portions of the building model so that you can see inside. Each face of the section box acts as a cutting plane, so you can use the section box to create a wide variety of views to share your design and show the details of how it will be constructed—for example, 3D plans, 3D sections, and 3D detail views.

You can assign materials to the elements in a building model to accurately display their appearance in shaded and rendered views. All elements in a building model have a material—either a default material based on the object category or a specific material that has been assigned through the element’s type or instance properties.

Materials are assigned to elements using this hierarchy:

• Defaults—using default materials, which typically display a solid gray color.

• Object style—using the materials assigned to an object category or subcategory.

• Type properties—using the materials assigned to all elements of the same type in the family’s type properties.

• Instance properties—using the materials assigned to a single element through its instance properties.

If an element has properties that assign a material at a higher level in this hierarchy, lower-level settings will be overridden. For example, a furniture element that has materials assigned through its type properties will use those materials, rather than the default material assigned to the furniture category.

Review Questions

If you cannot find material settings in an element’s type or instance properties, how can you assign materials to the object?

Changing an element’s type or instance properties are high-level ways to edit materials assigned to the object. If these options are not available, the object style for the category that the element belongs to can be changed.

For example, if a door is displayed as gray and material options are not available in its type or instance properties, you can change the object styles for the Door category in order to set a default material for all door components.

What are the advantages and disadvantages of assigning materials as type properties versus instance properties?

Instance properties allow for an easier way to create variability between multiple instances of the same component. If we have multiple objects that we would like to be different materials, instance properties allow us to change each one individually.

However, if we want to change the material of many instances at the same time (like a large set of chairs), assigning materials as a type property is much easier.

If you want to define a new material for some elements in your model, is it better to change an existing material or to duplicate one and change the settings of the new material?

It is typically better to duplicate a similar material when creating a new one. This prevents you from deleting a useful material or accidentally changing a material that is being used elsewhere in the project.

Revit software includes an extensive library of predefined materials and rendering appearances, and you can edit the existing materials or duplicate them to create new ones as needed for your design.

Use the Material tool in the Manage tab to edit existing materials, create new ones, and specify how the materials will be displayed in views.

You can set these options for hidden line, shaded, and consistent color views:

• Shading color

• Transparency

• Surface patterns (for cut and uncut surfaces)

You can also assign a render appearance to each of the materials that will be displayed:

• Views set to use the realistic visual style.

• Photorealistic views created using Revit software’s rendering tools (which we will learn about in the next lesson).

To change a material’s render appearance, open the Materials dialog box, then switch to the Render Appearance tab, where you can browse the library of render appearances by material type or search to find specific items. You can:

• Replace the current render appearance by choosing a new one from the library.

• Adjust the settings to change or fine-tune the current render appearance.

Review Questions

If you want to change the render appearance of some of the elements in your model, is it better to modify an existing material’s settings or to create new material and assign it to those elements?

If you are sure that you want to change the render appearance of every element using a specific material, then it is generally okay to modify the render appearance of that existing material. Otherwise, create new material for each element that needs to be altered.

When creating new render appearances from photographs or scanned images of materials, what types of images work best?

Pictures and images with repeated patterns and limited distortions caused by a poor camera angle work best for creating new render appearances.

Review Questions

What types of building elements are typically affected when refining BIM models to match the building process?

Construction methods can vary greatly due to variations in the construction techniques commonly used for different building materials. For example, the sequence of operations and erection strategy is typically very different for steel-frame versus concrete-frame structures.

The elements that are most often in need of refinement include:

  • Items that are easily modeled as spanning several floor levels – for example, structural columns and exterior walls. Although these elements will align at each floor level, they will likely be built one or two levels at a time.

  • Items that are modeled as multi-layered structures, which are actually building in several discrete steps – for example, floor and roof types that include both structural and finish layers in the type definition.

A good overall guideline is that the elements in the BIM model should be broken into pieces that closely reflect the likely construction process.

Review Questions

What are the essential differences to consider when modeling steel or wood versus concrete building systems?

Steel framing, wood framing, and pre-cast concrete are examples of stick-built systems, composed of placing and assembling lots of individual elements. As these individual elements are modeled, precise placement at the proper height and with the appropriate joining conditions is critical to avoid interferences and create accurate models that will be useful for construction planning and structural analysis.

Cast-in-place concrete is an example of a monolithic system, created by building temporary formwork and then placing concrete (and reinforcing materials) in the forms. The individual building elements (columns, beams, slabs) typically merge into a singular monolith when the concrete placed, so overlaps and intersections between these model elements are appropriate.

Review Questions

What are the advantages of using 3D details compared to 2D details?

The focus of all detailing is to accurately convey your design intent to the people who will be constructing it. So, any technique that enables you to convey this intent more clearly and avoid any misunderstandings and mistakes is a better vehicle for communication.

3D views are often easier to understand than 2D section callouts, which abstract a 3D model into a 2D representation where one dimension of the spatial information is lost or hidden. 2D details still serve an important role in construction documents, but for important connections where the spatial relationships may not be completely clear in a 2D view, 3D details can assist in explaining your design intent more clearly.

When should exploded 3D views be used?

Use exploded views to expose hidden or difficult-to-understand elements or layers to make it clearer to the people who will construct your design where one element starts and the next one begins.

Review Questions

What is the advantage of using search sets versus selection sets for selecting model elements in Navisworks Manage?

As model elements are changed, search sets dynamically update to select all of the model elements that meet the search criteria. Selection sets are static. Once defined, they do not change automatically. So, as new elements are added to a model, you must adjust the selection sets manually.

What is the advantage of adding task IDs to building elements in Revit to manage schedule linking?

Adding task IDs to building elements a Revit model makes it easy to automatically link those elements to construction tasks. By defining search sets that select model elements based on these task IDs, you can quickly select the elements related to a specific task and link them to the project timeline. This approach is much quicker and easier than defining search sets in Navisworks Manage based on element properties, such as name or type. You can use the powerful selection features available in Revit (for example, drag selection, filtering by category, select all instances, and custom search filters) to easily select groups of elements, then control the task linking by editing the values of the task ID parameter.

Review Questions

How do location-based workflows improve construction schedules?

Location-based workflows divide large schedule tasks into smaller ones, based on the work area in which they will be performed. These smaller tasks can typically be sequenced into parallel workflows that greatly reduce the delays of waiting for large tasks to be completed sequentially. Using location-based scheduling, construction planners can optimize and balance crew sizes to create smooth flows of tasks, constrained primarily by the availability of the work areas. And the reduction of the delays between individual tasks typically yields big savings in the overall project schedule.

Review Questions

How can construction planners use parts to improve construction simulations?

By breaking multi-layer building elements into parts, construction planners can create more accurate simulations of planned construction operations. For example, the individual layers and materials of a multi-layer wall are typically installed at different times—first, the structural core layers, followed by the exterior cladding and weatherproofing layers, and finally, the interior finish layers after the building are weathertight. Breaking the wall into parts enables the different layers to be assigned to the right craft crews and scheduled at the appropriate time in the project timeline. While the modeling efficiency of creating multi-layer elements benefits the design process, from a construction modeling perspective, these layers should be separated and worked with independently.

Review Questions

What is the advantage of using design options in Revit for comparing and analyzing conceptual designs?

By using design options, you can easily apply any special views or schedules you define to analyze your design to evaluate each alternative. Using this approach, you create master views that can be applied to all design options, then update and enhance them in one place.

To apply these views to specific design alternatives, duplicate the view and adjust the visibility graphics overrides for that view to display the desired design option. You can also display the views and schedules for several design options side-by-side on a sheet for each comparison and presentation.

Why is using conceptual masses a better approach for conceptual design?

Conceptual masses enable you to quickly model and explore different building shapes, massing, and placement—some of the most important decisions to be made during conceptual design—without getting distracted by the details of modeling and editing individual building elements. You can easily convert the faces of the conceptual mass into building elements after deciding upon the desired shape.

Review Questions

What factors should be considered when comparing projects to establish conceptual cost metrics?

When using comparable building projects to establish cost metrics to be used in preparing a conceptual estimate, it is critical to adapt and scale the data to accurately the new project conditions and differences from the projects used as the basis for comparison. For example, it is common to apply adjustments that consider the effects of differences in project scale, project location, uses and functions, and appropriate inflation factors. Conceptual estimating is both an art and a science. But, experienced estimators can create amazing accurate conceptual estimates to confirm the feasibility of a proposed design and provide a target value for continuing design work.

Review Questions

What types of building elements are typically quantified... Using counts?

Counts (each) are typically used to quantity components that are installed as individual units—for example, doors, windows, skylights, fixtures, furniture, lighting, structural framing elements, and so on. Length (LF) is used to quantify elements where the cost will depend on the length installed—for example, railing, piping, fascia, and so on. Area (SF) is used to describe elements with a common thickness, where the cost will depend on the area installed—for example, wall assemblies, roof assemblies, material surfaces, and so on. Volume (CF) is typically used to quantify elements whose shape and volume will determine by external constraints—for example, cast-in-place concrete or expanding foam insulation.

What are the best sources for cost data?

The best source for cost data is a firm’s historical records. The actual data from past projects take into account all of the specific features of a firm’s techniques, construction strategy, and management style, so it is by far the most accurate predictor of future costs. For this reason, it is vitally important for firms to keep accurate cost accounting records for current projects. The data affects not only the current project but also impacts the reliability of future predictions. When historical data is not available, estimators typically rely on external cost sourcebooks and online databases for cost information. When external cost sources are used, it is critical to adapt and scale the numbers provided to accurately reflect the specific project conditions and differences from the norms. For example, it is common to apply adjustments that consider the effects of project scale, project location, local labor costs differences, materials cost differences, and appropriate inflation factors.

Review Questions

What kind of data is tracked to assist with space planning activities?

Space planners typically track information on a room-by-room basis. The values tracked can include: room area; room volume; maximum occupancy; whether a room is assignable; which department it is assigned to; the names of the occupants; the current use; the materials (floor, wall, ceiling) in that room; key codes; and so on. The Revit platform provides the flexibility to add new parameters to the project model to support the space planning and facilities management needs of the building managers as they are defined and updated.

Review Questions

What type of information is typically tracked for building components to support preventive maintenance activities?

To support and track preventive maintenance activities, many building managers track these values for the building components: installation date, expected life cycle, expected replacement data, estimated replacement cost, and maintenance history. Using these values building managers can schedule planned maintenance and replacement activities and budget the associated costs.

Review Questions

What is the advantage of using shared parameters versus project parameters for facilities management information?

The issue of what type of parameter to use when adding data fields to your building model depends on how widely that type of information will be used. Project parameters can appear in schedules, but cannot be used in tags or shared with other projects or external data editors. They can be assigned to multiple categories within a single project. Shared parameters are more versatile. They can be shared by multiple projects and families, exported to ODBC, and appear in schedules as well as tags.

What is the advantage of linking a Revit project model to an external database editor?

Linking a Revit project model to an external database or asset management system enables other users of the facilities' information who are not facile with Revit to easily access and update the values they need in their familiar tools. The building data needs to access and flow between the various systems, but it is not necessary for all users to be working within the Revit environment.

Are there other tools available for linking Revit data to spreadsheets and other editors?

The Revit DB Link add-in provides an easy way to link Revit data to a Microsoft Access database. One important limitation of Revit DB Link is that the database must originally be created using it; databases that have already been created using other systems cannot be linked with this tool. There are a number of good commercially available tools for linking Revit project data to SQL databases and spreadsheets for editing and updating. Search the web to find the latest list and view comparisons of their features and advantages.