November 14th, 2012

Roof plans that need help from elevation views


Roof plans should be a simple bunch.  Measure the overhangs, center some ridges, draw 45 degree angles along the hips and Bam! Roof plan.  Of course, those of us spending way too much time measuring the real world know that it’s not always so smooth.  Sometimes we can’t even draw an accurate roof plan with drawing at least two of the corresponding elevation views.  Check out the south & west elevations of this beautiful home.

In this case we needed to go back and forth between the roof plan and the two elevations in order to make sure the roof plan was accurate.

November 2nd, 2012

Creating a Building Information Model of a Custom House

While we normally measure buildings to generate our drawings, sometimes we work from sets of two-dimensional architectural drawings. In this case, the challenge was to work from a set including exterior elevations, plans and a section in order to create what is called a building information model. The drawings were done in the late Seventies, when people were drawing by hand as opposed to using CAD, meaning that dimensions and alignment were not always accurate. Even now, with CAD as the industry standard, drawings are still prone to error when it comes to coordinating multiple two-dimensional views of a complex three-dimensional shape

With the arrival of new CAD software that automatically makes all 2D representations part of a 3D model that contains all the information about a project, known as a building information model, if alignments are off there will be error messages and glaring mistakes in the model. Take this process rendering for example. When the vertical stone element was extruded based on the two-dimensional hand drawings we were given, all of a sudden other walls began to intersect that stone element. That was impossible in the 2D era. The rendering also shows the limitations of building information modeling (BIM), because if you compare it to the photograph the pitch of the roof is different. The BIM model has an obvious hole in it where the roof is supposed to angle down to the right and overhang toward the adjacent slope. Overall, BIM is a great way to make sure that all of the two-dimensional drawings line up perfectly, because they are all based on one 3D model. Often, however, in order to do things accurate to the way they are (supposed to be) constructed, it requires that the software ‘understands’ whether or not an angled surface is supposed to be a roof or a wall, for instance. In the real world, BIM is the best thing ever for repetitive buildings made of standard parts. Customization in the software (Revit in this case) is still cumbersome for projects that require uniquely crafted details in their construction.

November 2nd, 2012

Creating a Building Information Model of a Custom House (Part 2)


In part one of this two-part entry, we saw how BIM is still difficult for smaller projects (such as detached houses) that have been highly customized. In this entry, I am showing the changes that were made after surveying the building. In most cases, this made the project easier to draft. In other cases, the limitations of BIM became obvious once I discovered the reality behind the way different features were constructed, many of which were not obvious from the hand drawings mentioned in part one. And all the mistakes are still obvious when examining the 3D model. The 2D drawings that BIM creates are still solid when you have the true dimensions of the rooms, which is much easier to achieve by visiting the site and measuring the project than by drafting from someone else’s (non-BIM) documentation.