[plug] planning software

[Gavin Chester]

Looking for advice on a linux gpl (of course) app to help with planning 
all stages of building a house. I am engaging contractors, but have 
designed it myself and want control and a record of all the elements of 
the build, such as specifying all the detail like plumbing diameters, 
fixtures, etc. In other words, an app to encompass the generalities and 
have nested within it minute details room by room.

I _think_ I want something that might be a cross between a mindmap app 
and a project planning app. I have no experience with either, so am 
seeking your recommendations if you know something suitable. I've had a 
look at "planner" and "kplato", but I'm not sure that gantt charts and 
such are what I want compared to some sort of inventory/scheduling type 
of app. Maybe it is? Any ideas?

Gavin