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  • Culver Epps

BIM first steps and issues

The main problem that arose during the transition to Archicad from flat CAD was making sure the templates that Allan developed (and continues to develop) and model parts were standardised to our method of working. Two problems arose early days;

1. Working in food production means that most floors are not consistently at the same level and have many intricate falls and drainage is an inherent part of the design.

2. Walls are also not simple to model as they are usually built on stainless steel kerbs (or derivatives thereof) and doors do not cut kerbs as we need.

So, how do we solve these issues. Not easily it seemed and we struggled with the best way to get over it with the tools and limited knowledge we had at the time. Until (and this is honest) I had a eureka moment whilst walking to the pub on a Saturday afternoon. So excited was I, I immediately texted Allan to tell him the plan. It was good in theory, but like most theories I had to implement it. Now, those of you that have met me, and know me, know that I am a 'colossal nerd' and the prospect of learning a modelling language to overcome our issues was a challenge I relished.

I had to learn GDL (Geometric Description Language) which is part of the Archicad toolset

Food safe white wall with double sided stainless steel kerb

Let's start with the 'easier' of the 2 problems. Allan managed to create nearly all of our wall types using a tool called 'Complex Profiles', however, the kerb being outside the line of wall itself was creating door cutting issues in plan. So we decided to develop our own door model which we could control how the floor plan was drawn. This meant that I had to develop a 3D parametric model as well as a 2D parametric model.

Here is how they look;


2D view of Cox Freeman Door Object

As you can see the kerbs can be cut at an angle which is much more the preferred option to some Clients. However, the offset from jamb can be adjusted (as the image below). Parameters include;

Door Pockets (on/off)



The code was much simpler than I had anticipated and we agreed that any ironmongery which was part of the parametric model would not be shown in the plan view but would be generated in the 3D view. The 3D view was not so simple but having spent most of my teenage life using BBC Basic the usage of GOSUB and RETURN were very useful in developing a more manageable modelling code, which was interchangeable dependant on elements chosen. Also, 3D modelling is similar to explaining how flat CAD draws to someone who has never used a computer to draw before;

1. Set specific elements of the pen - colour, width etc. These are specific variables setup in the settings window.

3. Start the function.

4. Locate start position of the pen.

5. Put pen on paper.

6. Draw line a specific length.

7. Pick up pen.

8. End the function.

One thing that I had not allowed for before beginning was that 3D Archicad models are coded on their backs - Z axis is actually the Y axis and visa versa. Once this is overcome it was a matter of designing the door as a matter of slabs. A lot of code was learnt and looking back on it I have difficulty in deciphering my own code.

The only problem which has not been overcome as yet is clipping of the kerb and not the door opening. When a door is positioned in the wall it cuts the kerb at the position of the door reveal. So, the 2D drawing is correct yet the 3D model does not cut the kerb as required. This is a limitation of Archicad, although I think it could be done using two cuts in the wall and then inserting the door.

3D view of Cox Freeman Door Object

Anyway, enough of being a nerd for the time being. Next time I'll tackle the floor slabs. That issue was far more interesting...and painful.

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