How to Read Floor Plans, Elevations and Sections: A Step-by-Step Guide

What you need before you start

Architects, surveyors and planning officers describe buildings with three kinds of drawing. Once you can read them you can check a builder’s quote, follow a planning application, decide where furniture and lights should go, and spot problems before they cost money.

You need very little: a printed set of drawings (or a screen you can zoom), a pencil, a ruler marked in millimetres, and a calculator. Most drawings you will meet use a conventional metric scale. Councils typically ask for floor plans and elevations at 1:50 or 1:100,^[1][2] and Historic England’s recording guidance says hand-drawn plans are typically 1:100 or 1:50, with sections at 1:50 or 1:20.^[3] This guide works in millimetres throughout, so you never need a special scale rule.

The three views: plan, elevation and section

Each view is a flat, orthographic drawing: it shows true shapes and proportions with no perspective, which is why you can measure from it.^[4]

• Plan. A horizontal section through the building, looked at from above. It is usually cut about 1.2 m (4 ft) above the finished floor, so it shows walls, door and window openings and fittings; features above the cut, such as beams, are drawn dashed.^[4][5]
• Elevation. A flat view of one outside face of the building, named after the compass direction it faces: the north elevation is the north-facing wall.^[6]
• Section. A vertical slice through the building. Cut elements are drawn with bold lines, often filled solid, and things seen beyond the cut with thinner lines.^[5] A section is where you read heights: floor to ceiling, floor to floor, roof pitch.

The three are linked. A plan carries section marks (for example A–A1) showing where the vertical slice was taken and which way you are looking.^[3] A window on the plan must appear in the same place on the elevation, which is a useful way to catch drawing errors.

How to read a floor plan, step by step

1. Find the scale. Look in the title block or beside a scale bar. Some councils will not accept drawings marked “not to scale” or “do not scale”.^[1] If a PDF has been resized, the printed scale is wrong, but a scale bar shrinks with the page, so measure the bar instead.
2. Find north and the entrance. Planning guidance asks for a north point on location and layout plans.^[1] In recording drawings of single buildings the main entrance is usually at the bottom of the sheet.^[3]
3. Read the room names. Floor plans submitted for planning show the layout with room names.^[7] Walk the route from the entrance in your head.
4. Trace the walls. Thick, solid shapes are cut walls. External walls are normally thicker than partitions.
5. Find the openings. A gap with an arc is a door and shows which way it swings; a gap with thin parallel lines is a window.
6. Use written dimensions first. Only scale what is not written. Wikipedia’s summary of drawing practice notes that dimensions should be written on the drawing because copying can introduce errors.^[5] Many planning drawings carry just one significant dimension.^[7]
7. Check line styles. Dashed lines usually mean something above the cut, hidden, or existing and to be removed.^[7]

Symbols and line weights you will meet

Conventions vary between offices, but the logic is consistent. Heavier lines mean cut material; lighter lines mean things seen below or beyond the cut; dashed lines mean something hidden, above the cut, or to be removed.^[5][3] Hatching or solid fill shows what the cut passes through, and the style of crosshatching traditionally indicates the material.^[4] Historic England’s guide includes standard symbols for walls, former walls, doors, windows, beams, fireplaces and stairs.^[3]

The engraved plan below, published by Ottavio Bertotti Scamozzi in 1778 from Palladio’s Villa Rotonda, uses the same logic almost 250 years on: the cut walls are solid black, openings are gaps, steps are drawn as parallel lines, and sizes are written along the rooms.^[8]

Scale: turning a drawn length into a real one

A scale of 1:50 means one unit on the drawing equals 50 of the same unit in the building. Work in millimetres: real length = drawn length × scale number. A wall that measures 84 mm on a 1:50 drawing is 84 × 50 = 4,200 mm, or 4.2 m. On a 1:100 drawing the same wall is 42 mm. Going the other way, drawn length = real length ÷ scale number.

Scale off a drawing only for rough planning. One council’s guidance says that if a warning is needed it should read “Do not scale for construction purposes”,^[2] and any figure you need for ordering should come from a written dimension or a site measurement.

How to read an elevation

An elevation shows one face flat on, so nothing shows depth. Check four things. First, the label: planning guidance asks for elevations to be named North, South, East or West (or to show a north point) rather than front, back and side.^[2] Second, the ground line and the levels, such as finished floor and ridge. Third, the materials note, since elevations should indicate the type and colour of finishing materials.^[1] Fourth, dashed outlines: on a planning drawing, demolition or replacement work shows the existing extent as dashed lines.^[7]

Then cross-check with the plan. Every window and door on the elevation should line up with an opening on the plan, and a chimney breast on the plan should show as a stack above the roof.

How to read a section

A section answers what a plan cannot: how high the ceiling is, how thick the floor is, how steep the roof is. Historic England describes measured cross-sections as showing vertical relationships such as floor and ceiling heights and roof truss form.^[3]

1. Find the section line on the plan and the arrows showing the viewing direction.
2. Find the bold, filled shapes: those are the walls, floors and roof the slice passes through.
3. Read the levels. Planning guidance asks sections to give finished floor and ridge levels against a datum, usually Ordnance Datum (AOD).^[1]
4. Calculate heights by subtraction. Floor-to-ceiling = ceiling level minus finished floor level.
5. Note thin lines beyond the cut: they are things you would see further back, not material the slice passes through.

Worked example: a small plan at 1:50

Imagine a 1:50 plan of a living room. You measure with a ruler and multiply by 50. The numbers below are invented for the exercise; the method is the real thing.

Check it: a door of 900 mm in a 4,800 mm wall looks sensible, and a 2.4 m ceiling over a 17 m² room is a normal proportion. If a result looks absurd, you have probably used the wrong scale.

Common mistakes

• Trusting a printed scale after resizing. Measure the scale bar instead.
• Reading heights from a plan. Heights belong to sections and elevations.
• Confusing existing and proposed work. Check the key and line styles; most applications show both.^[1]
• Forgetting what the dimension runs to. Room sizes may be to wall faces or wall centres. Floor areas are conventionally measured to the internal face of the perimeter walls.^[9]
• Ignoring door swings. A door that clashes with a radiator or a bed is easy to spot on the plan and expensive to find on site.
• Treating the drawing as the building. Historic surveys stress recording what is actually there, and old rooms are rarely square.^[10]

Quick reference

The table summarises what each drawing is for. Scales are those quoted by planning guidance and by Historic England.

Detail scales are as given in Wikipedia’s summary of architectural drawing, which cites 1:10, 1:5 and full size for details and 1:20 for wall layers.^[5]

Glossary

Terms you will see on drawings.

What to do next

Pick one real drawing, such as your own house’s plan, and work through the seven steps with a ruler. Then measure your actual room and draw it: our guide to measuring a room and drawing a scale plan picks up where this one ends. If you are working on a period home, the guide to identifying the period of your house shows how to read what the building itself is telling you.

Keep reading

• How to measure a room and draw a scale plan
• Identify the period of your house from plasterwork
• Making small rooms feel bigger
• How to measure for an overdoor
• Palladio and the pediment
• Styling a hallway with architectural details

Shop the look

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Frequently asked questions

What is the difference between a floor plan, an elevation and a section?

A floor plan is a horizontal slice through a building seen from above. An elevation is a flat view of one outside face. A section is a vertical slice through the building that shows heights and construction.

At what height is a floor plan cut?

By convention a plan is drawn as a horizontal cut about 1.2 m (4 ft) above the finished floor, so that walls, door and window openings and fittings appear. Features above the cut are often shown dashed.

What scale are floor plans usually drawn at?

Councils typically ask for floor plans at 1:50 or 1:100, and Historic England says hand-drawn plans are typically 1:100 or 1:50, with sections at 1:50 or 1:20.

How do I work out a real length from a drawing?

Measure the drawn length in millimetres and multiply by the scale number. A line of 84 mm on a 1:50 drawing is 84 × 50 = 4,200 mm, which is 4.2 m. Use a written dimension if one is given.

What does a dashed line mean on a plan?

Usually something above the cut, hidden from view, or existing and to be removed. Check the key on the drawing, because conventions differ slightly between offices.

Why are elevations named north, south, east and west?

Naming them by compass direction removes any doubt about which face is meant. Planning guidance asks for elevations to be labelled in this way or to show a north point, instead of front, back and side.

Can I rely on the dimensions on a drawing?

Treat written dimensions as the best information on the drawing, but check important ones on site. Old buildings in particular are rarely square or exactly as drawn.

What is a section line?

A mark on a plan, often labelled A–A, showing where a vertical section was cut and which way the viewer is looking. The matching section is labelled with the same letters.