Any building is an extremely complex arrangement of structural members, mechanical systems, and finishes. In order for builders to turn an architect's idea into an actual building, a complete set of several different kinds of construction plans is necessary. Local building authorities also require appropriate plans before they'll issue a building permit, so a complete set of plans is a legal requirement as well as a practical one.
Floor and Foundation Plans
A floor plan is essentially an overhead view of a building or addition with the roof and upper floors removed, as if the viewer is looking down on the building from above. A floor plan shows the location of exterior and interior walls; it also typically shows the location of major features of the building, such as staircases, doors, windows, plumbing fixtures and major appliances. Floor plans usually also include room names and dimensions, and they may also include additional information such as square footage and ceiling heights. A foundation plan is similar to a floor plan, but a foundation plan shows details of the foundation's structure, including foundation walls and slabs, footings, and support posts.
Like a floor plan, a framing plan is an overhead view of a structure, but a framing plan shows details of the building's structural members, including roof rafters, trusses, ceiling and floor joists, and support beams and headers. Framing plans are used to help builders understand and lay out the complex structures of roofs and floors.
Mechanical plans also resemble floor plans in that they are usually drawn from an overhead point of view, but mechanical plans show the location and specifications of the building's mechanical systems. Individual mechanical plans may show details of the structure's electrical wiring, heating and air conditioning system and ductwork, gas lines and meters, and plumbing. Plans will also typically include the location of relevant appliances, hard-wired smoke detectors, and other permanent fixtures that depend on the depicted mechanical system.
Cross Sections and Elevations
Cross sections and elevations are both side-on views of the structure, as if the viewer is standing beside the building. Elevations show the exterior of the building, and they provide information about doors, windows, roofing and exterior finishes. They may also show details of the ground's slope around the building's foundation. Cross sections are cutaway views, as if the building had been cut in half from the roof to the ground level or below. Cross sections are used to show details of the structure's interior framing and foundation. They are useful because they allow the inclusion of vertical structural members that are not visible in overhead views.
A site plan is an overhead view that shows the building in the wider overall context of the entire site. A site plan includes information about lot boundaries and dimensions, sewer and septic systems, utility services, grade and elevation changes, drainage systems, landscaping, and pavement.