How to Read a Floor Plan: Symbols, Dimensions and Doors

The five things to find first on any floor plan

Knowing how to read a floor plan comes down to five things: the north arrow, the scale, the wall lines, the dimension strings and the door swings. Find those and the rest of the drawing explains itself. Furniture, fixtures and labels are detail layered on top.

In our Indore studio we hand over a floor plan with a short walk through, because most clients have never read a technical drawing. They nod at the 3D view, sign off the plan, and then discover on site that the toilet door hits the wardrobe. A plan read properly at the drawing stage avoids almost all of that.

1. North arrow: tells you which way the plot faces and where morning light comes from. Without it you cannot judge Vastu, ventilation or sun.
2. Scale: usually 1:100 for a full plan (1 cm on paper is 1 m on site) or 1:50 for a detailed room. The title block states it.
3. Wall lines: thick double lines with the gap filled or hatched. The gap is the wall thickness, usually 9 inch outside and 4.5 inch inside.
4. Dimension strings: lines with small ticks and a number in between. They give the size of each room and the overall building.
5. Door swings: a quarter circle from the hinge side. The arc is the floor the door needs to open.

If you are still at the stage of deciding which plan to pick, our pillar guide on how to choose a house plan that suits your plot and family comes before this one.

Lines: what thick, thin and dashed mean

A floor plan is a horizontal cut through the house at about 4 ft above the floor, looking down. Anything the cut passes through (walls, columns, door frames) is drawn heavy. Anything below the cut (floor, furniture, platform) is drawn light. Anything above the cut (a loft, a beam, a projection) is drawn dashed.

A quick test: if you can walk into it, it is drawn thin; if you would bump into it, it is thick. That one habit makes floor plan symbols far less confusing.

Doors and windows: reading the swing and the width

A floor plan door swing is drawn as a straight line (the leaf, open at 90 degrees) with a quarter circle arc from the hinge. The arc is not decoration. It is the floor that must stay clear for the door to open. Draw a bed or wardrobe inside that arc and the door hits it every day.

The width is written beside the door or given in a schedule as D1, D2 and so on. Typical sizes we use are 3 ft 6 in for the main door, 3 ft for bedrooms and 2 ft 6 in for toilets. Anything under 2 ft 6 in is a cupboard, not a door.

• Does the door swing into the room (right for bedrooms) or into the passage (blocks movement)?
• Do two doors near a corner clash when both are open? Common at toilet and bedroom door pairs.
• Does a toilet door open directly into the living or dining room?
• Is the main door wide enough to bring in a fridge or a 6 ft sofa?

Windows show as a thin triple line in the wall gap, often with a W1 or W2 label and a size such as 4x4 (width by height in feet). Sill height is on the elevation or the window schedule, not the plan; a standard sill is 2 ft 9 in to 3 ft. Every habitable room needs at least one window to an external wall or a shaft. A bedroom with no window symbol is not legally a bedroom in most bylaws. Our guide to natural light and ventilation in Indian house design is a good companion here.

Dimensions: the numbers that matter and the ones that mislead

Reading house plan dimensions is where most people go wrong, because there are three different numbers for every room and plans do not always say which one is written.

• Centre to centre: wall centre line to wall centre line. Used by engineers. Larger than what you see.
• Outer to outer: outside face to outside face. Used for built-up area.
• Clear or carpet: inside face to inside face. The room you actually walk in. Smallest of the three.

A bedroom labelled 12x14 ft is often centre to centre. Clear of a 4.5 inch wall on each side, the room you furnish is 11 ft 3 in by 13 ft 3 in. On a 10x11 room that loss matters. We write clear sizes inside each room and dimension strings outside, so the client sees both. Ask your architect which convention the drawing follows.

Dimension strings run in chains. The outer chain gives the total length; inner chains break it into rooms and walls. Add up an inner chain and it must equal the outer figure. If it does not, something was moved and not updated, and that is exactly the kind of error that becomes a 6 inch gap on site.

Municipal drawings are in millimetres (a 900 mm door) while most client facing plans are in feet and inches. A 3,000 mm figure is 9 ft 10 in, not 10 ft, and that difference adds up across a 30 ft wide house.

Fixtures, furniture and the abbreviations on the plan

Once you can read walls and openings, the fixtures tell you how each room is meant to be used. Here are the common house plan abbreviations and symbols you will meet.

Furniture on a plan is drawn at real size. Our interior design team insists on this, because a bed drawn at 4x6 ft to make a room look roomy is the oldest trick in the trade. Measure the bed symbol against the scale; a queen bed should read 5 ft by 6 ft 6 in. If it reads smaller, the room is smaller than it looks.

The kitchen deserves a second look: platform 2 ft deep, at least 3 ft clear between parallel platforms, and the sink under a window. Our note on modular kitchen layouts and standard sizes explains what each kitchen shape needs.

Stairs, levels and what a plan does not show

A staircase shows as a row of parallel lines (the treads) with an arrow and the word UP. A diagonal break line means the stair continues above the cut height. Count the treads: a 10 ft floor height at a 7 inch rise needs 17 risers. If the plan shows 12 treads for that height, each step is too tall. Tread depth should be 10 to 11 inches.

• Ceiling and sill heights: on the section drawing or elevation, not the plan.
• Beam positions and depths: on the structural drawings; a beam can cut into a loft or door head.
• Floor levels: marked as +0.00, +0.45 and so on; check the toilet floor sits 1 to 2 inches lower than the room.
• What the house looks like: that is the elevation, not the plan.

For how the stair position changes the whole plan, especially on narrow plots, see our post on the best staircase position in a house plan.

A ten minute method to review any floor plan

This is the check we run with clients before a plan goes for approval. It takes about ten minutes with a pencil.

1. Find north and the scale. Note which rooms get morning sun and which face the street.
2. Trace the walk from the gate to the main door to the living room. Does it pass a toilet door?
3. Walk every passage with your finger. Mark anything under 3 ft 6 in wide.
4. Open every door in your head. Mark any arc that hits another door, a bed or a wardrobe.
5. Check each bedroom for a window on an external wall or shaft.
6. Add up one dimension chain and compare it with the overall figure.
7. Measure the bed, sofa and dining table against the scale.
8. Count stair risers and check tread depth.
9. Look for a filled column at every wall junction.

Clients who do this once rarely need a plan explained again. It also helps when comparing a drawing against finished examples in our house plans gallery to see how the symbols turn into rooms.

Next step: have your plan read with you

If you already have a floor plan from a builder or draftsman and want a second pair of eyes, our floor plan design service includes a review session where we mark up door clashes, dark rooms and dimension errors before anything is built.

Call the studio on +91 73165 33888 or write to us through the contact page for a free first consultation.