How to read a floor plan: every symbol explained

What the arcs, the hatched blocks, the paired lines and the numbers on an architectural floor plan actually mean, so you can check a builder's drawing instead of nodding at it.

A floor plan is a horizontal slice through a house at about waist height, looking down. Everything cut by that slice (walls, doors, windows) is drawn heavily. Everything below it is drawn lightly. Everything above it, like overhead cupboards, is usually dashed.

Once you know that, most of the symbols explain themselves. Here is the rest.

Walls

The heaviest lines on the drawing. Thickness is drawn to scale, so an external wall reads visibly thicker than an internal one: in conventional Australian construction that's about 230mm external (brick veneer) against 110mm internal (90mm stud plus 10mm plasterboard each side).

Solid black or heavily hatched walls are existing or structural. On renovation drawings, new walls are commonly shown in a different hatch or tone from existing ones, and demolished walls dashed. There's no universal convention, which is why every proper drawing set has a legend: read it first.

Doors

The one symbol everyone half-knows. A door is drawn as a gap in the wall, a line for the leaf, and an arc showing the swing.

The arc matters more than it looks. It tells you three things: which way the door opens, which side the hinges are on, and how much floor it sweeps. That swept floor is space you cannot put anything in, which is why door swings are where amateur plans most often go wrong: two doors clashing, or a door that opens onto a light switch.

Other door types:

• Sliding door: a leaf drawn offset from the opening, no arc. Takes no floor space.
• Cavity slider: the leaf disappears into the wall; drawn as a gap with the leaf inside the wall thickness.
• Cased opening: a gap with no leaf and no arc. A doorway with no door.
• Bifold: a zigzag of leaves.
• Garage door: a wide gap on an external wall, often with a light dashed line showing the panel travel.

Windows

Drawn as a break in the wall with thin parallel lines across it: typically three lines, representing the frame and glass. Unlike doors, they don't sweep floor space, so there's no arc.

What a plan usually doesn't tell you is the sill height (how far off the floor the window starts) because that's a vertical dimension and a plan is horizontal. That lives in the window schedule or the elevations. It matters: a window with a 900mm sill sits above a benchtop; one at 600mm doesn't.

Room labels and areas

Each room gets a name and usually an area in square metres. Two things to check:

• Is the area internal or including walls? Internal is normal for room areas. The house's total is often quoted as a different figure again: see below.
• Do the room areas plus the walls add up to the external footprint? On a real drawing they do. On a sketch, never.

Australian marketing floor plans also quote a total area which may or may not include the garage, alfresco and porch. "Living area 186m², total under roof 232m²" is the honest form. A single number with no breakdown is a number to ask about.

Dimensions

Thin lines with ticks or arrows at each end, and a number in the middle. Read as millimetres in Australia, essentially always: "3600" means 3.6 metres. A plan in metres or feet will say so.

Dimension strings are usually layered: an overall external dimension on the outside, then a string breaking the building into bays, then internal room dimensions. Check the strings add up. If the parts don't sum to the overall, something has been changed and not redrawn.

Dimensions are also either to structure or to internal faces, and which one changes the number by a wall thickness. Good drawings say. If yours doesn't, ask, because a room dimensioned 3000 to studs is a room that finishes at about 2980 once it's lined.

Fixtures and fittings

Mostly little plan-view outlines of the real object, and mostly recognisable once you're looking down:

• Kitchen: a bench run drawn as a band along the wall, with a circle or two for the sink, and a square with four small circles for the cooktop. An island is a free-standing rectangle. Dashed lines above the bench are overhead cupboards.
• Bathroom: a rectangle with a curve for the basin, a rounded shape for the toilet pan, a square with a diagonal or a quarter-arc for the shower (the diagonal is the screen or the fall to the waste), and a plain deep rectangle for the bath.
• Laundry: a tub, plus one or two squares for the machines.
• Stairs: parallel lines for the treads, with an arrow marked UP or DN. On multi-storey plans the stair appears on both floors, cut by the slice.
• Robes and cupboards: a rectangle with a thin line or a zigzag for the hanging rail.

The things people miss

North point. A small arrow or compass. It decides which rooms get morning sun and whether that "sunny" living room faces south. If a plan has no north point, you cannot evaluate it.

Scale. Written as a ratio, usually 1:100 for an Australian house plan, on A3. At 1:100, 1mm on paper is 100mm built, so a 3600mm wall measures 36mm. Check it before you scale anything off the drawing with a ruler, and check the sheet hasn't been printed at "fit to page", which silently invalidates the scale.

Section markers. A line across the plan with arrows and a letter at each end, showing where a vertical section is cut and which way it looks. The section drawing is where ceiling heights live.

Hatched or shaded floor areas. Usually a change of floor finish: tiles against timber, or a slab against a deck.

Checking a plan rather than admiring it

A short list that catches most real problems:

1. Walk it in your head. Front door, groceries to the kitchen, bedroom to bathroom at 2am. Count how many rooms you pass through.
2. Check every door swing for clashes with other doors, walls, switches and cupboards.
3. Check hallway widths. 1000mm is the minimum; under that, it's a tunnel.
4. Check bed and furniture fit. A queen bed is 1530 × 2030. Draw it in and see what's left.
5. Find the wet areas. Bathroom, ensuite and laundry close together is cheaper to plumb than scattered.
6. Check the north point against the living areas.
7. Add up the dimension strings.

If a plan fails one of these, it's a question to ask, not necessarily a mistake. Plans are compromises. The point is to know which compromises you're accepting.

Reading your own plan back

The fastest way to learn the symbols is to draw with them. Draftie draws in the conventions above, walls to scale by thickness, doors with real swings you can flip, windows with sill heights, room labels with areas, dimension strings as you drag, and exports at 1:100 with a north point, so what you produce reads like the drawings you'll be handed.

FAQ

What scale are Australian floor plans drawn at?

1:100 on A3 is the residential convention. 1:50 is used for kitchen and bathroom detail, and 1:200 for site plans. At 1:100, one millimetre on the page is 100mm built.

Are floor plan dimensions in mm or metres?

Millimetres, almost always, in Australia. A dimension reading "3600" is 3.6 metres. Drawings that use metres normally label the units explicitly.

What does the arc on a door mean?

It shows the swing: which way the door opens, which side the hinges are on, and how much floor the leaf sweeps. That swept area has to stay clear, which is why it's drawn.

Why are some lines dashed on a floor plan?

Dashed lines usually mean something above the cut line: overhead kitchen cupboards, a bulkhead, the outline of a roof or awning over a deck. On renovation drawings they can also mean demolition. The legend on the drawing says which.

Does the floor area on a plan include the walls?

Room areas are normally measured internally. A house's total area is often quoted differently again and may or may not include the garage, porch and alfresco, so ask for the breakdown rather than comparing single numbers between plans.

What is a north point and why does it matter?

A small arrow showing which way north is. It determines sun into each room: in Australia, north-facing living areas get winter sun, and west-facing glass gets hot afternoon sun. A plan without one can't be assessed for orientation.

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General information for Australian residential projects, not professional advice. Product specifications and prices change, confirm current details with the manufacturer or supplier before you rely on them. Draftie produces concept plans, not construction documents.