Once you receive the floor plan from your architect, you will see dimensions on the outer wall of the house plan. In Kenya, we use metric system whereby all dimensions are in milli meters. Other countries use dimensions in feet and inches. A very easy way to convert feet to millimeters is to use the conversion tool on your mobile phone or use a tape measure and check out the dimension in meters then turn the tape measure on the opposite side that is in feet and inches then check the corresponding dimension.
The outer dimension shows the start and end of the building.
The middle dimension shows the room sizes.
The inner dimension shows the openings i.e doors and window sizes. The Local Authority in Kenya specifies how the architect should dimension the floor plans before submitting the plans to the council for approvals.
Spot heights are dimensions showing the floor to ceiling height. They are usually shown on the architectural floor plan with a circle divided into 2 parts with a dimension next to it.