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How to read a floor plan

Part of the questions on Floor plans

Read a floor plan in four passes: the numbers along the edges are lengths, on HDB plans in millimetres, so 3150 is 3.15 m; the lines are walls, drawn thick and solid where they are structure; the quarter-circles are doors and the way they swing; and the labels name each room.

The numbers

The figures strung along the outside of the plan are dimensions: the length of the stretch of wall between two tick marks. On the HDB plans Setout has been tested with they are in millimetres, with no unit written, so 3150 means 3,150 mm, or 3.15 m. A row of shorter figures usually adds up to the long one printed outside it: check that it does, and you know you are reading them right.

Areas are a separate matter. HDB quotes two for a new flat: the internal floor area, which is what you furnish, and a total that also counts the air-con ledge. To turn square metres into square feet, use the converter.

The walls

Walls are drawn as they would look sliced through at about waist height. On an HDB plan some are thick and filled solid black, and others are a thin pair of lines. The solid ones are the structure. HDB’s own renovation guide says some walls in a flat are reinforced concrete, which keeps the flat structurally sound, and HDB does not allow structural members such as reinforced concrete walls, columns and beams to be hacked or removed.

So a layout that depends on removing a thick black wall is not one to plan around. Setout reads those walls off an imported plan and locks them for the same reason. Thin walls may be another matter, but hacking any wall needs a permit from HDB first.

Doors, windows and labels

  • A quarter-circle with a straight line is a door: the line is the door standing open, the arc is the floor it sweeps. Nothing tall can stand inside that arc.
  • A V across a doorway is a folding door, as often drawn for a bathroom.
  • Thin lines within a wall are a window.
  • A gap in a wall with nothing drawn in it is an opening you walk through.
  • Labels name the rooms.

Checking the scale

A plan that has been photographed, photocopied or resized no longer matches any scale printed on it, so do not measure it with a ruler. Trust the printed dimensions instead. In Setout you set the scale by dragging across one dimension you know and giving its length; every other length on the plan then follows from that.

Sources

Rules and fees change. The linked page is the authority; if it differs from this one, go by it, and tell us.

Questions

What unit are the measurements on an HDB floor plan?

Millimetres, on the HDB plans Setout has been tested with: 3150 means 3,150 mm, which is 3.15 m. Areas are given separately in square metres.

What do the thick black walls on a floor plan mean?

They are the structure. HDB says some walls in a flat are reinforced concrete and does not allow structural members such as reinforced concrete walls, columns and beams to be hacked or removed.

What does the curved line at a door mean?

It is the door’s swing: the straight line is the door standing open and the quarter-circle is the floor it passes over as it shuts. Furniture cannot stand inside it.

The quickest way to read a plan is to stand in it.

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