Architecture Floor Plan
An architecture floor plan is the drawing of a building cut horizontally at a level just above the floor, and it is the primary document of the discipline of architecture, the one drawing from which the whole building is read. The floor plan shows the layout, where each room is, how big it is, and how a person moves from one space to the next, and it is the drawing that the design of a building is built around. This page defines the floor plan, explains the scales and the symbols it uses, and shows how the plan drives the design of the building.
What a floor plan is and why it is the primary drawing
A floor plan is a horizontal cut through a building, drawn at a level about 4 feet above the floor so that the walls, the doors and the windows all show, and it is the primary drawing of the discipline because it shows the layout, which is the first and most important decision in the design of a building. A floor plan is drawn to scale, usually 1 inch to 50 feet for an overall plan or 1 inch to 10 feet for a detailed one, and it carries the dimensions of the rooms, the position of the openings and the notes that fix the materials. A floor plan for a single story house is a single drawing, and for a multi story building there is one plan per floor, a set of 3 to 6 drawings for a building of that size. The plan is the primary drawing because the building is lived in as a layout, and a person who lives in a house lives in the plan, moving through the rooms in the order the plan sets, which is why the design of a building starts with the plan and not with the view.
The scales a floor plan is drawn at
A floor plan is drawn at a scale that fits the drawing to the paper, and the scale is chosen so that the building can be read and measured from the drawing. The table gives the scale, the name it is known by, and the building it is used for.
| Scale | Used for | What it shows well |
|---|---|---|
| 1:200 to 1:500 | The site and the block | The building's position and its context |
| 1:50 to 1:100 | The overall floor plan | The layout and the room sizes |
| 1:20 to 1:50 | A single room or level | The furniture and the fixtures |
| 1:5 to 1:1 | A detail on the plan | The join at the wall or the door |
The scale of the floor plan is fixed by what it has to show. A site plan at 1:500 shows the building on the land, an overall plan at 1:100 shows the layout, and a room plan at 1:20 shows the furniture and the fixtures that fit the room. The same building is drawn at all 4 scales, and the set of plans at different scales is what makes the drawing complete, because each scale shows a different layer of the design. A floor plan drawn at the wrong scale is a plan that either hides the detail or hides the whole, and the discipline's skill is in choosing the scale that shows the layer the drawing is for.
The symbols and conventions a floor plan uses
A floor plan is read by its symbols, and the conventions of the floor plan are a standard language that every reader of the drawing knows. The walls are drawn as thick lines, the openings as gaps in the wall, the doors as an arc that shows the swing, the windows as a thin line in the wall, and the fixed furniture, the sink, the stove and the toilet, as standardized shapes. The dimensions are carried on lines outside the plan, the north arrow shows the orientation, and the level, the height of the floor above a datum, is written on the plan. A floor plan uses 10 to 20 of these symbols on a single sheet, and the reader of the plan reads the building from them. The conventions are standard because the drawing is read by people who did not make it, the builder, the code reviewer and the client, and a plan that breaks the convention is a plan that has to be explained, which is where the errors and the delays come in.
How the floor plan drives the design of the building
The floor plan drives the design of the building because the layout is the first decision and the decisions that follow from it. Once the plan is fixed, the sections, the elevations and the details follow, because the section is the plan seen from the side, the elevation is the plan seen from the front, and the detail is the plan zoomed in. A change to the plan changes all 3, which is why the plan is drawn first and why it is the drawing the client is asked to approve before the design moves on. The plan also drives the building's performance, because the layout decides the flow of the person, the light that reaches the rooms and the structure that carries the floors. A floor plan that is well drawn is a plan that makes the building work, and the design of a building is, at its heart, the design of its floor plan, the layout that the whole structure is built around and the drawing from which the building is read.