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Reading a floor plan: symbols, dimensions and practical tips

Updated: 2026-07-12 · Reading time: 12 min · ImmoLens editorial team

A Grundriss (floor plan) is the most important technical drawing when buying a property. It shows the layout of the rooms from above and reveals at a glance whether a flat or a house suits your lifestyle. Yet many buyers underestimate how much information a floor plan holds, and how easily you can be misled by attractive visualisations.

1. The most important floor plan symbols

Every floor plan uses standardised symbols. Once you know them, you can read any plan:

2. Reading dimension lines: Rohbaumaß or Fertigmaß?

A dimensioned floor plan carries Maßketten (dimension chains), usually several in parallel. The outermost chain gives the overall dimensions of the building, the middle ones the axes and openings, the innermost the clear room dimensions, which is what you can actually furnish. If the dimension chains are missing and only square metre figures are printed in the rooms, you are missing exactly the information you need.

The classic trap is the difference between Rohbaumaß and Fertigmaß. The Rohbaumaß (structural dimension) describes the state without plaster, screed and floor covering. The Fertigmaß (finished dimension) is what is left after the fit-out. New-build plans often show Rohbaumaße. Reckon on around 1.5 cm of plaster per wall face: a room therefore ends up about 3 cm shorter in each direction than the plan claims.

3. Living area under the WoFlV: what really counts

Living area is not the same as floor area. Under the Wohnflächenverordnung (WoFlV, the German living area ordinance), areas count to different degrees depending on the ceiling height:

What that means in practice is shown by a top-floor room with 30 m² of floor area under a pitched roof. Assume 10 m² lie below 1 m in height, 8 m² between 1 and 2 m, and 12 m² above that. Then the result is 0 + 4 + 12 = 16 m² of living area out of 30 m² of floor area. And a 12 m² balcony typically contributes only 3 m².

4. Judging room sizes and furniture space correctly

A common mistake: rooms look bigger in the floor plan than in reality. The scale 1:100 (the standard for flats) means that 1 cm on the plan equals 1 m in reality.

Square metres alone say little, though. What matters is the Stellfläche: an uninterrupted stretch of wall with no door, window or radiator. Work with these requirements and look for them in the plan:

• Bed with two bedside tables: 180 cm + 2 × 40 cm = 2.60 m of free wall.
• Three-seater sofa: a good 2.20 m, plus about 90 cm of walking space in front of it.
• Dining table for 6: The table measures roughly 90 × 180 cm. To pull the chairs out you need about 90 cm all round. The dining area therefore occupies around 2.70 × 3.60 m.
• Galley kitchen (two runs): at least 1.20 m between the runs, otherwise the oven and dishwasher doors cannot be opened while someone is standing there.

5. Why rooms look bigger on the plan

The plan shows an empty area. In reality there is furniture in it, and you have to walk between it. An item that is often overlooked is the door swing area: a room door with an 80 cm leaf sweeps a quarter circle of around 0.5 m² in which nothing may permanently stand. With four doors off a hallway, that is 2 m² that look like usable space on the plan.

The second reason is the furniture that is drawn in. Furnished sales floor plans like to draw it undersized: a "double bed" suddenly turns out to be only 140 cm wide, the sofa 1.60 m. That way every room looks generous.

6. Assessing proportions and layout

The ideal room shape is a rectangle with a side ratio of at most 2:1. Tube-shaped rooms (3:1 or narrower) are hard to furnish and feel cramped. Also pay attention to:

• Circulation routes: Is there a long hallway that "eats up" a lot of space?
• Room connections: Are the kitchen and living room directly connected? Is there an open living and dining area?
• Walk-through rooms: Do you have to pass through one room to reach another? That reduces privacy.
• Bathroom position: Is the bathroom close to the bedroom? Or do you have to go through the hallway?
• Space for furniture: Where do the wardrobe, bed and sofa go? Take radiators and socket positions into account.

7. Typical layout flaws in the plan

Some weaknesses can be solved with furniture. The following ones cannot. They are baked into the plan and you will keep them:

• Walk-through rooms: The room is only usable to a limited degree because someone is always walking through it. Practically unusable as a child's room or bedroom, and it can almost never be given its own access afterwards.
• Windowless internal rooms: The Landesbauordnungen (state building codes) require a window of a minimum size for Aufenthaltsräume (habitable rooms), often around one eighth of the room's floor area. A windowless room is therefore formally not a habitable room. It must not be counted as a room, even if the Exposé calls it one.
• Bathroom without a window: Permitted, but the moisture has to be removed mechanically. The fan has to run on, and if it fails, mould follows. A bathroom with a window forgives ventilation mistakes, an internal one does not.
• Kitchen without an external wall: The extractor hood cannot be ducted outside, leaving only recirculation with an activated carbon filter. Smells spread through the flat.
• Hallways that are too narrow: Below about 1.10 m, carrying furniture past each other becomes an exercise. For accessibility under DIN 18040-2, a hallway width of at least 1.20 m and a clear door width of 80 cm apply. If you are planning for the long term, that is the relevant benchmark.
• No free wall: A room with two doors, a window and a radiator may not have a single wall left that a wardrobe fits against. Check that before you buy, not on moving day.

8. What can be changed later, and what cannot

"We can always convert that" is the most expensive sentence in property buying. This overview shows what is realistic:

9. Compass direction and incoming light

The orientation of the windows determines how much natural light a room receives:

Two things qualify this table. First, shading: a south-facing window behind a tall neighbouring wall or under a deep balcony delivers considerably less in winter, when the sun is low, than the plan promises. Second, window size: a floor-to-ceiling window facing east brings in more light than a small window facing south. Check both on the plan, the sill height is usually noted at the window opening.

10. Checklist: checking a floor plan systematically

11. Typical mistakes when reading a floor plan

Mistake 2, trusting 3D renderings: Some Exposés (property brochures) only show attractive 3D views instead of to-scale floor plans. Always insist on a dimensioned plan.

Mistake 3, overlooking secondary areas: Hallway, storage room and utility room are often missing from the "Wohnfläche" (living area), but they contribute to how the home feels. Check the calculation for compliance with the WoFlV (Wohnflächenverordnung, the living area ordinance).