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Residential Extension


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Hi all,


Having successfully designed my first house in 3D, I'm now trying to implement BIM into a residential extension project but I am struggling to work out the best way to show the original property and the property with the extension added. Would it be sensible to build the existing model and then duplicate the entire model and add the extension? This seems the easiest way but it doesn’t feel like the correct way? I’m sure it can be done using layers and classes and turning them on/off etc. but I can't see how when it comes to merging the roofs together how to differentiate between old and new?


This link should allow you access the existing model if needed.


Thanks in advance.



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I work in a similar way. I simply duplicate the model within the same file. One set of design layers as an “-extg” suffix and is kept as reference while I work on the “-prop” design layers. 


The only downsides with duplicating the model, wether in the same file or in a seperate file, is that if updated or corrections are required to the extg it needs to be done on both models. For this reason it helps if the extg model is as accurate as possible so there are minimal updates required. 


Im interested to hear about other ways people set up alteration work.

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  • 3 months later...


I've only just ventured into this sub forum!


We use 3 separate files. One for the survey, then copied for planning, then planning copied for working drawings. This is because each file has a distinctly different objective/function. For example much of the working drawing detailing is done in 2d which "clogs up"  the file somewhat. On the rare occasions we have to go back to planning using a working drawing file it's always quite difficult and requires a lot of stripping out e.g !!  The planning file is often heavily rendered (unlike the WD file or the Survey) to make it look good so the focus there is on rendered visuals. As @Boh  says the survey is all about accuracy and making sure any "human errors" do not have latent issues on site a year later with a grumpy builder,  an even grumpier client (and possibly a planning enforcement officer)! so the survey is often a simple - and hopefully accurate - hidden line drawing.


Having 3 files also reduces the file sizes to a manegable level. We find they start to get a bit unstable/glitchy at +80,000 kb  The disadvantage is not being able to copy viewports over file to file (which haven't been copied originally)  but then again each workflow stage often requires new viewports (section cuts) any way.






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