When you try to generate a space from the outlines of walls, you may get unexpected space boundaries.
Generating spaces from object outlines can be useful for generating spaces that are deducted from other spaces, like a mass element representing a shaft, or walls that represent a construction space. A space generated from wall outlines should look like this: 
In some cases, the space generation may result in different and segmented boundaries like this: 
If this is the case, the maximum allowed gap size between boundary objects is too big, and the end wall conditions between walls are not calculated correctly. Recreate the space with a very small maximum gap size.