AEC definitions
A floor plan is a scaled drawing of one level of a building, drawn as if the building were cut horizontally and you were looking down. It shows walls, doors, windows, rooms, dimensions, and the tags that point to schedules and details.
Definition
The cut is typically taken about 4 feet above the floor, high enough to pass through windows and doors and low enough to miss most of the ceiling. What you see is orthographic, not a perspective. A floor plan locates the work. Heights live on sections and elevations. Finishes at the ceiling live on a reflected ceiling plan. The same level may appear as an architectural plan, a structural plan, and several MEP plans, each with its own information on a shared background.
In depth
Anything below the cut plane is drawn in the plan. Anything above it is generally omitted or shown dashed, unless a note says otherwise. That is why a floor plan can hide a soffit that a reflected ceiling plan makes obvious.
If a mezzanine, a split level, or a stair lands inside the cut, the drafter has to choose a plane and note it. A plan that changes cut height without saying so produces dimensions nobody can trace.
Find the north arrow, the scale, and the grid. Match the grid to the column schedule and to the structural plan. Room names and numbers should match the finish schedule. Door and window tags should match their schedules.
Dimension strings are hierarchical. Overall, then openings, then interior. A string that does not add up to the overall is a drawing error, and it is worth an RFI before the wall is laid out. Do not average the disagreement in the field.
The architectural plan owns rooms and partitions. The structural plan owns slabs, beams, and openings through them. Mechanical, electrical, plumbing, and fire protection plans show their devices on the architectural background. They are not four opinions about where the wall is.
When a device plan and the architectural plan disagree about a wall location, the architectural plan is usually the background that was supposed to win, at the revision the engineers were given. Check the background date before you pick a line.
A site plan shows the building on the land. A roof plan shows the roof, not the top occupied floor. A reflected ceiling plan looks up at the ceiling of the same level. An equipment plan may repeat the architectural background for one trade.
A marketing plan or a test-fit is often a floor plan with no contractual status. The title block tells you whether the sheet is issued. A furniture layout from leasing is not a construction floor plan.
Moving a wall on the floor plan moves the reflected ceiling, the finish tags, the structural opening if there is one, and every MEP plan that used the old background. A revision cloud on A-101 only is incomplete if the other sheets still show the old line.
That is why late plan changes are expensive. The geometry is small. The sheets that depend on it are not.
Examples
A-101 is the level-one floor plan at 1/8 inch to the foot. Door tags on that sheet match the door schedule. Section marks point to sheets A-301 and A-302.
The electrical lighting plan uses the architectural background but does not restate partition types. The wall rating is read on the architectural plan.
A tenant test-fit shows a pantry the construction floor plan deleted by addendum. The bid follows the addendum, not the test-fit.
FAQ
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