How to read a floor plan

What a floor plan shows

The imaginary cut is made roughly at window height, so the plan shows the walls where they are cut through, the doors and windows in them, and everything below: fixed fittings like kitchen counters and bathroom fittings, and often the furniture. Things above the cut, such as beams, lofts or high cabinets, are usually shown as dashed lines.

A plan shows lengths and widths, not heights. For heights you need the sections and elevations that come with it, which the plan points to with section marks.

1. Start with the north arrow and the scale

The north arrow tells you how the building sits on its site, and so where the morning and evening light will come from. In India it is also the first thing many families check, because of Vastu preferences for where the kitchen, bedrooms or pooja room should face.

The scale tells you how big the drawing is compared with the building. Metric plans are usually drawn at 1:100 for a whole floor, where one centimetre on paper is one metre on site, and at 1:50 for a closer look at a flat or a room. Imperial plans use scales such as ¼ inch to a foot.

One caution: a plan printed or zoomed to a different size is no longer at the scale written on it. Trust the scale bar, which grows and shrinks with the drawing, and the written dimensions, never a ruler held to a screen.

2. Read the dimensions

Dimensions run in strings outside the plan: usually the overall length on the outer line, then wall to wall, then the openings. On metric drawings they are in millimetres, so 3600 means 3.6 metres. Indian drawings often give both, with room sizes written as 12'-0" × 14'-0" as well.

Inside each room you will usually find its name and size, width first. Check the drawing's notes for whether sizes are measured to the finished faces of the walls or to their centre lines, because the difference can be a few centimetres on each side.

3. Walls and columns

Walls are the thick lines, filled solid or hatched where they are cut. Their thickness tells you what they are. In Indian homes, outer brick walls are commonly 230 mm (9 inches) thick and inner partitions 115 mm (4½ inches). In timber and steel-stud construction, as in much of North America, partitions are thinner, around 100 to 125 mm.

Solid squares or circles in or along the walls are columns, the building's frame. They cannot move, which matters when anyone wants to open up a room later.

4. Doors and windows

A door is a gap in the wall with a straight line for the door leaf and a quarter-circle arc for the way it swings. The arc shows which way the door opens and the floor space it needs. Sliding doors are drawn as two thin overlapping panels inside the opening.

Windows are thin parallel lines within the wall: the frame and the glass. Their heights are not on the plan. Codes such as D1, D2 or W3 point to a door and window schedule that gives each one's size and sill height, and on Indian drawings V usually marks a ventilator, the small high window in a toilet.

5. Stairs, levels and what is overhead

Stairs are drawn as a series of lines, one per tread, with an arrow marked UP or DN from the floor you are looking at. A zigzag break line shows where the plan's cut passes through the flight.

Level marks such as FFL +0.00 or +0.45 give the finished floor level of each area. A step between rooms, a sunken bathroom or a raised deck shows up here. Dashed lines usually mean something above the cut, or on renovation drawings, something to be removed.

6. Fixtures and furniture

Bathroom fittings, kitchen counters and appliances are drawn with simple symbols. Furniture is often drawn too, to prove a room works: that a bed fits with space to walk around it, or that a dining table seats eight. Treat drawn furniture as a proposal, not a fixed part of the plan.

For the full set of symbols, with a chart, see floor plan symbols and what they mean.

Reading a plan with a client

Most clients nod at a plan they cannot really read. They understand rooms: where they will sit, cook and sleep. Walk them through it in the order they will live in it, from the front door, one room at a time, and tell them what each room will look and feel like before you talk about dimensions.