Size in Counter-Strike
Here are some normal heights and width you should at all time be aware of.
Doors A door, like those in cs_mansion is the size of 64x92.
Rooms A normal room has the height of 128 units.
Windows Windows like in cs_mansion are 64x64 units.
Walls The walls in cs_mansion are 16 units width.
Cs_mansion and success You dont have to do everything just like mansion, but this map is allmost older than counter-strike, therefore it has more or less defined the size of everything. Keping close to these standarts will help you in having success with your maps.