Monday, February 15, 2021


 My “studying history with BIM” work goes back many years, but the pivotal moment in terms of public engagement was Project Soane.  That was also the thing that got me deeper into the Classical Orders and how to represent them in Revit, having made a start via discussions with Paul Aubin over the preceding year or so.  Paul and I tend to have “different but complimentary” approaches, which is great.

After that came Notre Dame, and some truly collaborative work, diving into the Gothic tradition which sits between the classicism of Late Antiquity and the classical revival from the Renaissance onwards.  That’s a huge sweep of European history, stretching well into the era of global trade and the industrial revolution which was already underway during John Soane’s lifetime.


Then came a period of parallel styles, mostly “revivals” of some kind, including very strident arguments pitting Classical against Gothic.  Polarisation of opinion is not altogether a new phenomenon although it does seem to ebb and flow.  In recent weeks I have stumbled into the work of Victor Horta, towards the end of the 19th Century.  People were trying to find a way of moving into the future, to find a “style of today” or even a way to progress beyond the notion of “style” as a set of formal conventions.  One of these days I will get back to looking at the Arts & Crafts movement which was part of that search for a new direction.  But right now it’s the turn of Art Nouveau, a much more lavish and hedonistic approach to generating form.

All the same, there is often a deep attachment to ideas we would associate with Arts & Crafts, or even modernism.  Looking at the window grille by Hector Guimard which I photographed in the Victoria & Albert Museum in London in 2017, I was fascinated by the way he used standard mild steel sections, executing simple cuts and bends, just as blacksmiths had been doing for generations, but generating wildly organic shapes, as if by magic.  So this is not just willful nonsense, as you might think at first sight, but an attempt to work within craft traditions while heading in new directions.

Back to Baron Victor Horta and the Maison Hallet in Brussels.

I decided to tackle the cloakroom window next to the street entrance.  I had used a placeholder family here.  Just a cut opening, drawn in a wall-hosted template and assigned to the Windows category but with no timber framing of glass, and not picking up on the subtle inflections of the stone facing.  I am assuming this is limestone, carved by hand.  It could have been faience (cast ceramic) but I don’t think so in this case.




I have to convert an opening cut into a void extrusion.  This is because you can’t mix the two in the same wall-hosted family and I need some stepped rebates to take this family to the next level.  Luckily we can copy-paste the same sketch lines used for the cut opening to define the void extrusion.

  • Select the cut opening
  • Edit
  • Select all the sketch lines
  • Copy to clipboard
  • Close the sketch
  • Delete the cut opening
  • Create void extrusion
  • Paste aligned to selected levels
  • Choose ref level
  • Close the sketch.


The void will probably not be cutting the wall.  So you have to use “Cut Geometry”  Also it may well be using the centre-line of the wall as its Work Plane, so Edit Work Plane and specify “Back” not sure why that’s the name of the work plane that is locked to the face of the wall, maybe because it’s the back of an object that sits on the face of the wall. Don’t expect templates the date back to the earliest version of Revit to always work the way you might have wanted them to.

Now it’s cutting right through the wall, but that’s only because the wall is 150 and the extrusion defaulted to 250 (6” & 8”) When I bring it into the project the wall will be 500mm thick so I will have a recess.  Sometimes that’s what you want, and you can always add a parameter to control the depth.  Either way we need a reference plane parallel with the wall.  Lock the void extrusion to that, and lock the reference plane to the inner face of the wall.

That takes us back to where we started from, but with the crucial difference that Revit will allow us to add further voids.  First I modified the shape of the main extrusion to pick up more of Horta’s subtle curves.  Then I added a shallow void extrusion to cut some delicate rebates in the top edge of the lower openings.  These have the effect of tricking the eye into seeing vestigial capitals atop the columns that divide this lower portion into three parts.  It’s a clever little detail that I hadn’t noticed before, one of those little bonus observations that come your way when you put in the effort of trying to recreate someone else’s work.  That applies whether you are drawing it by hand, modelling in Max or Sketchup, or going “full BIM”.  But the BIM pencil is the most demanding of your attention and offers deeper insights in my experience.



One small aside.  Shapes that taper away to nothing can be challenging in Revit.  That’s why the “triangles” in my sketch end with a radius rather than a sharp point.  Just stay alert for this possibility when you get an error message saying Revit can’t make that geometry.  Revit doesn’t like tiny little short lines, and it doesn’t like tiny little thin slivers.  There are always limits, you just need a plan for adapting to that reality.

My third extrusion was a big rectangle on the inside half of the wall.  When I added this I pulled the outer void back so these two meet in the middle.  That’s because I wanted the inner sill to be slightly higher than the outer sills.  I’m thinking about rain water.

None of this is parametric.  I could add a certain amount of parametric behaviour later if I thought it offered some value, but right now this is a one off and flexing the size is going to be a nightmare with all these subtle curves.  Maybe that’s a bit strong.  It’s going to consume quite a lot of time and effort which doesn’t seem justified for current purposes.



So the two solid extrusions to represent wooden frame and glass are also free of constraints and parameters.  Just practicing eye-balling in these tricky shapes.  It’s all good practice.  Drawing with the mouse using Revit’s little palette of tools.  I placed a little groove to represent the rectangular outlines of the inner frames, which could be hinged or fixed.  I really don’t know and I’m not too concerned right now.  Much more interested in taking a crack at the external grille.

This has something in common with the one by Guimard that I showed at the beginning, but Horta is just working with flat bar.  It’s more delicate and the fixing rivets are becoming more significant in adding to the organic feel, as if they are little buds on some climbing vine perhaps.  I could spend a lot longer capturing this, and adding the ones on the entrance door, but there are lots more windows, plus balcony railings.  I had to decide how far to take this exercise, the purpose of which is to increase my understanding of Horta’s work. 

So… I wrapped up my day with an image that combines shaded and rendered views in photoshop with a bit of masking and “coloured pencil” filtering, shared that to LinkedIn and signed off.


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