How to Read Architectural Floor Plans

Floor plans can look like a maze of lines, numbers and symbols the first time you open one. Once you know the conventions, though, they become the clearest way to understand a building: far more precise than a 3D render. This guide explains what you are looking at, step by step, so you can study a plan with confidence before you buy it or discuss it with a builder.

What a floor plan actually shows

A floor plan is a horizontal slice through the building, typically about 1 to 1.5 m above the floor, seen from directly above. Everything cut by that imaginary plane, mainly walls, is drawn with heavy lines. Things below the cut, such as floor finishes, kitchen counters and furniture, are drawn with lighter lines. Things above the cut, such as upper cabinets or beams, are often shown dashed.

Each level of the house has its own floor plan. Read them together: the stair on the ground floor should line up with the stair on the upper floor.

Start with the title block and scale

Most drawing sheets have a title block, usually along the bottom or right edge, giving the drawing name, the scale and the sheet number. Common scales are:

• 1:100 and 1:50 in metric drawings. At 1:100, 1 cm on paper is 1 m in reality; at 1:50, 2 cm on paper is 1 m.
• 1/4 inch = 1 foot (roughly 1:48) and 1/8 inch = 1 foot (roughly 1:96) in imperial drawings.

A scale is only valid when the drawing is printed at the stated paper size. If you print an A3 sheet on A4, everything shrinks. That is why written dimensions are more reliable than measuring the paper with a ruler.

Reading dimensions

Dimension lines are thin lines with ticks, dots or arrows at each end and a number above. Plans usually have several layers of dimensions around the outside:

• the outermost line gives the overall length of the building
• the next line in breaks it down into major sections such as wall to wall
• the inner lines locate openings such as windows and doors

Metric plans are usually dimensioned in centimetres or millimetres; the title block or notes tell you which. Imperial plans use feet and inches, for example 12'-6" (twelve feet six inches). Room sizes are sometimes written inside each room, as width by length. Our guide to metric vs imperial plans explains how to convert.

Walls

Walls are the heaviest lines on the plan. External walls are usually thicker than internal ones because they carry insulation and cladding. Hatching or solid fill inside a wall can indicate its material or whether it is load-bearing; the legend explains the convention used on that drawing set.

Doors and windows

• Doors are drawn as a gap in the wall with a line for the door leaf and an arc showing which way it swings. Sliding doors are drawn as two overlapping lines within the wall thickness. Check that door swings do not clash with each other or with furniture.
• Windows appear as thin parallel lines within the wall. The sill height and window height are not visible on the plan; you find them on the elevations or in a window schedule.

Stairs

Stairs are drawn as a series of parallel lines (the treads) with an arrow showing the direction of travel, often labelled UP or DN. Because the floor plan cuts through the stair partway up, there is usually a diagonal break line where the drawing stops. The number of treads and their depth determine how steep the stair is.

Kitchens, bathrooms and fixed items

Kitchen worktops, sinks, hobs, toilets, basins, showers and baths are drawn with standard simplified symbols. They help you judge whether the rooms are usable, but their exact positions may change during detailed design. Check that there is enough space in front of fittings to use them comfortably.

Section marks and elevation marks

You will often see symbols such as a circle with a letter or number and an arrow, connected by a line across the plan. These are section marks: they show where a vertical section has been cut and in which direction you are looking. The section itself appears on another sheet, labelled with the same reference, such as Section A-A.

Elevation marks work in a similar way, pointing to the views of each façade. Reading plans, sections and elevations together is how you understand heights, roof shape and levels.

North arrow and orientation

A north arrow shows how the building is oriented. It matters because sunlight, views and wind all depend on direction. On a ready-made plan the arrow is only a suggestion; when the house is placed on your plot, the real orientation may differ. See how to choose a house plan for your plot.

Common abbreviations

Abbreviation	Meaning
UP / DN	Stair direction, up or down
WC	Toilet
W/D or WM	Washer and dryer, washing machine
REF	Refrigerator
CL or WIC	Closet, walk-in closet
FFL	Finished floor level
CH	Ceiling height
TYP	Typical, applies to similar elements
EXIST	Existing

Abbreviations vary between countries and offices, so always check the legend on the drawing set you have.

A simple method for studying a plan

1. Find the front door and walk through the house in your mind.
2. Note where natural light comes from in each room.
3. Check room sizes against furniture you own.
4. Look at the sections to understand ceiling heights.
5. Check the elevations to see window heights and the roof.
6. Write down questions for your builder or architect.

Try it on one of our plans, for example this 138 m2 three-bedroom house or a single storey 143 m2 classic house. Every plan page lists the files included; selected house plans include real-size 1:1 DWG/DXF files in centimetres, which you can open in CAD to measure any element directly. Read what's included in a house plan set for details.