BIM has become the industry standard for planning, design and construction documentation on commercial projects. We believe it should be the standard on all projects, including residential.
Architects produce drawings. Historically all of these drawings were created by hand. With the advent of computer aided drafting (CAD), this process was made much faster and easier, but the basic idea of making a drawing did not change. AutoCAD replaced pens and pencils, but the buildings architects designed still had to be described one 2D drawing at a time – plans, sections, and elevations. It is normal to digitally overlay one drawing over another, but fundamentally each drawing is an independent entity.
Building Information Modeling (BIM) changes the way that drawings are produced in a way that CAD doesn’t. We are still using a computer to create a set of 2D drawings, but the idea of a BIM project is that you model the building as it would actually be built in three dimensions, and, as much as possible, the program takes care of the drawings for you. Whereas a CAD project requires a lot of time thinking: “how should this be drawn?” an ideal BIM project only requires asking: “how should this be built?”
In reality of course, we still take time trying to get our drawings to read correctly (and look good!). However, the move from a CAD design process to one using BIM greatly reduces the amount of time spent thinking about drawings, and greatly increases the amount of time working though how your building will actually come together in real life.
We use a program, Revit, which is one of many pieces of BIM software available. BIM is an emerging field that goes beyond building design into facility and energy management and even into construction scheduling on large projects. But using BIM provides great benefits to the design of single family residences and even partial remodels. Below are a few of the ways that Revit and BIM add value to our process:
Visualization
Because we model every project in three dimensions, it is easy to produce perspective views which help us and the client to understand how proposed spaces will feel. Many architects will us a 3D program or physical models in very early design to get a feel for a projects massing, and then start over as the project is translated to 2D CAD drawings for design development. However, since a BIM workflow is in 3D the entire time, we can add detail directly on to our massing studies, and continue to easily provide 3D visualizations through all stages of design.
Preliminary massing studies for single family residence. When we settled on a direction with the client, we were able to use the masses to place our walls, roofs, and windows, rather than starting over and re-creating the project as a series of 2D CAD drawings.
Study of flat vs vaulted ceiling for single family residence remodel. Revit contains “design option” functionality that allows us to develop multiple solutions in parallel without holding up the rest of the design, which can continue to progress around them.
A promotional rendering for a small housing development
Interior renderings for single family residence remodel. Having a 3D model lets us quickly test different materials and finishes, and gives the client a much better idea of what the finished spaces will be like.
3D “flyby” of a proposed 9-home gated community in Kent, WA. Videos such as this one generated in Revit can be powerful visualization tools, and helpful with site analysis especially for larger projects with multiple buildings.
Coordination
Window and door schedule tags on Revit drawings acquire their number from each individual window and door they are placed on in the model. Numbering is an example of one of the many “built-in” properties each piece of the 3D model possesses.
Revit automates the scheduling of all its building components. In residences, that means that Revit creates our window and door schedules for us and keeps them always up-to-date. The schedules are linked directly to the model of a door or window, which means that it can never be showing the “wrong” size or height: whatever is shown in the schedule will be what is modeled in the 3D space. This is an extremely powerful tool that allows us take the time we would be spending coordinating between schedules and other drawings and use it improving the design.
The fact that schedules update in real-time also means you can answer questions quickly, and see how your decision would affect various metrics. For instance, we use Revit’s scheduling capability to track floor area, exterior envelope area, volume, and others in order to calculate the required heating equipment for the building.
Solar Studies
Animation showing shadows cast throughout the day at a precise date and location
Because we can tell the BIM model exactly where in the world the project is located, it is very easy to address site-specific solar questions, and to know exactly where the sun will be in relation to your modeled project on a specific time and day.
In the project shown below, the client wanted a couple of large, stacked decks to allow their living space to expand to the outdoors and to take advantage of the views to Puget Sound from their property. We used Revit to quickly generate a series of solar studies to see how much light would reach the lower level deck and living spaces, and worked with the client to balance their need for natural light with the desire for deck space above. Sunshades and deep eaves on the exterior also helped to manage solar gain in the summer time, but not block light in the winter. Revit helped us to analyze the size of the overhangs and sunshades for optimal performance throughout the year.
Project Phasing
Our model lets us track another dimension for each project: time. We are able to create different phases as needed for each BIM project and assign every model element to be created (or demolished) in a particular phase. That allows us to have an entire multi-stage project in one model, helping to test the practicality of the design and letting the requirements of each phase inform the design of the others. This is particularly useful for creating a Master Plan for future development, whether within a single house, or a large site with multiple buildings being proposed.
Using the tools available in Revit, and our knowledge of completing complex phased projects, we can help you find the optimal approach to completing your phased project.
Phase one construction of an outdoor gathering area
Phase two (same model, same view) with future addition visible over phase one gathering area
Phase one – a new single family residence
Future-phased geometry is independent of, yet related to the original house model
Clash Detection
When everything is modeled in 3D, we are able to see problems which are very hard to catch by looking at only 2D drawings. The 3D image above shows a sloping roof coming down over a stair corner with winder treads. As drawn, the ceiling interferes with the required head height at stairs (shown in green, with the interference outlined in red).
There are no 90 degree angles in that corner. The roof and stair have different slopes moving in different directions, and the interference is only over a small portion of the stair. Despite the fact that we had two sections in the area, this issue was missed by the City of Seattle in their permit review. If we worked solely with CAD / 2D drawings, it is likely that this issue would only have been caught in the field, where it would have been much less easy to fix.
A 3D view created to identify potential head height issues at a complex stair location
Generating Construction Documents
The 3D geometry of the model can’t by itself produce the detail required for a standard set of construction documents (yet!). Most municipalities require a typical wall section of a single location showing the assemblies that will be used throughout the project, at a level of detail that isn’t needed in other drawings. We generally do this by drawing 2D “detail lines” over our 3D modeled elements. It’s a little bit of CAD sneaking its way into our BIM process. However, unlike a pure CAD drawing, building the detail up from 3D modeled elements provides a base that guarantees coordination, as well as a very obvious check for future changes: whether the model elements and “detail lines” still align.
In general, BIM vastly reduces time spent on coordination. Change something in the 3D model, and it will show up in every one of the drawings immediately and automatically. AutoCAD projects would generally consist of dozens of separate drawings. Every change would require an architect to ask themselves: “does this effect anything in that drawing?” for every drawing in the project. introducing opportunity for errors.
A section taken through the physical Revit model (right) and 2D lines we normally use to add detail to the section (left).