# Problem with Substracting one Volume from another when measuring up house from the middle ages

Hey Guys!

We’ve recently gotten a new Project, which is to restore a house from the middle ages, built probably around 1100-1300.

My task now is, to measure the whole thing up and to make it into a 3d model, on which we can base our further steps.

Of course, since the house is that old and has moved quite a bit, we couldnt just go around and measure the length of the walls, since they are a different length every few centimeters, and also the angles are never 90°.

So we’ve decided to layout a grid, which means an Y,X and Z axis, from which we then would measure points. These points are now being typed into grasshopper, then connected with interpolate/polyline, then made into surfaces by using ruledsurface for the walls and patch for the ceiling and floor, and after that they are being transformed into meshs,breps or volumes…

Of course I am a beginner, and I am not sure whether grasshopper is the right tool for this, but it’s the one I’ve chosen and I want to learn more about it which is why I want to continue it.

Now to my real Problem:

Of course what we now measured is the inner surface of the rooms. What I need, to get it to work with vectorworks (the other programm my bureau is using), is to have the outer contuors of the rooms, basically the walls.

I’ve tried doing so by just placing a big box around it and then I tried to “subtract” the built rooms from the big box. But that didnt work. I’ve tried it with any old tool that I’ve found, nothing seems to work perfectly…

what works is, If I use solid difference, but only if I don’t extract the box all over it, which means it’s basically a floor plan. (which of course is what I need aswell but I need the thing as one, connected 3D thing of rooms).

I’ve only used grasshopper for that long and I’m not a native english speaker which makes it kind of hard for me to find the right answers.

However, I hope that you could help me a little bit, anything is appreciated! Thank you all!

Have a nice Weekend, Kind regards, Jonas!