Floor area ratio in the canton of Zurich

The garden has grown bigger over the years than the time left to tend it. Two rooms stand empty since the children moved out. On a walk, you notice a neighbouring house pulled down and rebuilt larger than before. The question arrives before anyone says it aloud: could our own plot hold more? The answer is not in the land register extract. It sits in a document from your municipality that almost nobody has read: the building and zoning ordinance.

And who decides which floor area ratio applies to your plot?

Who decides what may be built on your plot?

Three planning levels shape what is possible. The cantonal, regional and municipal structure plan (Richtplan) binds only the authorities, not you as the owner.¹ What binds your plot directly is your municipality’s building and zoning ordinance (BZO) with its zoning map – and, where one exists, a special-use plan (Gestaltungsplan): a separate plan for one specific area, with its own figures instead of the usual BZO. Every municipality must issue a BZO.¹

The BZO divides the municipal area into zones, for example residential zones, core zones or zones for public buildings.¹ For a single area, a detailed development plan (Quartierplan) can also apply, reshaping and servicing plots together.¹ You find your own zone on the ÖREB register, the canton’s official geoportal.³ It shows noise, building lines and other restrictions – but not the exact floor area ratio itself. That sits in your municipality’s BZO or in a special-use plan.³

What does the floor area ratio show for your plot?

The floor area ratio (Ausnützungsziffer, AZ) sets how much living and working space you may build, in relation to your plot area.¹ Floor area here means living and working space, including stairwells and corridors. This core concept has stayed the same under the old and new wording since 2017.¹²

A large parcel does not automatically mean a large building right. What matters is the ratio, not the area alone. A small plot with a high ratio can permit more. A large plot with a low ratio may permit less.

Your municipality’s BZO sets whether and which floor area ratio applies to your plot.¹ A special-use plan (Gestaltungsplan) can set its own figures for a single area.¹ Neither the ÖREB register nor your land register extract states this figure.³ What applies to the plot next door need not apply to yours.

What this means for you: ask your municipality’s building office about the BZO. Clarify your zone’s ratio before using any figure. The land potential check gives a first, non-binding reading.

Worked example

Worked example: how much reserve stays unused

An invented example with round figures, with no link to any real municipality.

Plot area: 800 m²
Assumed floor area ratio: 0.4
Permitted floor area (800 × 0.4): 320 m²
Floor area of the existing house: 180 m²
Unused reserve: 140 m²

Our own worked example under PBG section 255.¹ Your plot’s real floor area ratio is stated only in your municipality’s BZO – never in this example.

What do the building coverage ratio and the building volume ratio add?

The floor area ratio is not the only figure in the BZO. The building coverage ratio (Überbauungsziffer) sets how much of the plot the building may cover at ground level. This is its footprint.¹ It can be lower than the floor area ratio, for instance when several storeys are allowed.

The building volume ratio (Baumassenziffer) measures volume instead: the ratio of the building’s above-ground volume to the chargeable plot area.¹ It has stayed broadly similar, but falls under the same transitional rules as your BZO.

For your plot, the floor area, building coverage and building volume ratios all apply together. A high floor area ratio is of little use on its own. The coverage ratio can still force a narrow, tall building. Boundary setbacks and height limit what fits.

What this means for you: read all three ratios together, not the floor area ratio alone. An architect or your municipality’s building office can judge this. How much actually fits your own plot?

Must part of your plot stay green?

Many municipalities set a green area ratio (Grünflächenziffer) in their BZO. This is the share of your plot that must stay unsealed and unused for parking.¹ Municipalities that have not yet updated their BZO use the older open space ratio (Freiflächenziffer) instead. It covers play, rest and garden areas.¹²

Alongside this, the canton sets a minimum floor area ratio. Where the higher-level plan gives no density target, your municipality’s BZO must, as a rule, still provide a minimum. The figures below apply per number of storeys.¹

This figure is a legal minimum imposed on the municipality. It is not an automatic value for your individual plot. What actually applies in your zone can be higher, and is stated only in the BZO.

What this means for you: the green area ratio often limits what fits on your plot. It can do so even before the floor area ratio does. Check both together, not one alone.

Minimum floor area ratio every municipality must at least provide for
Storeys	Minimum floor area ratio
1 storey	20%
2 storeys	30%
3 storeys	50%
4 storeys	65%
more than 4 storeys	90%

A legal minimum imposed on the municipality, not a figure for an individual plot. Your plot’s actual floor area ratio is stated in your municipality’s BZO.¹

Does the entire plot area count towards the calculation?

Not necessarily. The calculation uses the chargeable plot area (anrechenbare Grundstücksfläche), not the area on your land register extract.¹ Land used for roads and service lines is usually deducted. A private driveway, however, is counted in.

In municipalities with an updated BZO, only the area actually lying within your building zone counts.¹ Part of your plot may lie in a different zone or a protected open zone. That part does not count towards your floor area ratio.

This can come as a surprise. A large overall parcel can therefore have only a small chargeable area.¹ The Federal Supreme Court has also explicitly rejected transferring floor area between zones with different rules.⁴

What this means for you: have the chargeable area of your plot clarified. Ask the building office, or use our land potential check. Do this before calculating with the whole parcel area.

How much of this realistically fits on your plot is shown by the land potential check, drawn from your municipality’s public records.

Start the land potential checkFree and without obligation · Personal reply from Dominik Devaja

Prefer to talk? +41 76 325 11 95 – you speak directly with Dominik Devaja.

Do the new terms already apply to your plot?

Perhaps not yet. The canton of Zurich harmonised its building terms in 2017. It did not adopt other cantons’ gross floor area ratio; Zurich kept the floor area ratio (Ausnützungsziffer).² The new wording only takes effect in your municipality once it has updated its BZO accordingly.

By law, municipalities have time to do this until 29 February 2028 at the latest.² Until a municipality has updated its own BZO, some of the earlier terms and ways of measuring continue to apply there.² Examples include building height (Gebäudehöhe) instead of facade height, or open space ratio instead of green area ratio.

The deadline was already extended once in 2026.² For your plot, only the BZO currently in force in your own municipality counts. Not a general date.

What this means for you: ask the building office whether your municipality has already adopted the new terms. We clarify this for you before giving any reading on your plot.

To be honest

When is the floor area ratio alone not enough?

The floor area ratio answers only part of the question. Boundary setbacks, building height, noise protection, the watercourse buffer or an ongoing development plan can all further limit the building volume allowed, regardless of the ratio itself.

A land potential check also replaces neither a feasibility study nor a building permit. It gives a first, non-binding reading from public sources – a binding building project needs an architect, a structural engineer and your municipality’s building office.

And sometimes developing simply is not right for you personally: if the years of commitment to a building project are too long, or if selling the plot settles the same decision faster and with less strain. Both are, for us, an equally valid path.

Frequently asked questions

What is the floor area ratio, simply explained?

It sets how much living and working space you may build, in relation to your plot area. Multiplied by your plot area, it gives the permitted floor area.

Where do I find the floor area ratio for my plot?

In your municipality’s building and zoning ordinance (BZO) or a special-use plan, not on the ÖREB register and not on your land register extract. The building office can tell you.

Is the floor area ratio the same across every Zurich municipality?

No. Each municipality sets its own floor area ratio per zone in its BZO, with a cantonal rule on minimum values where the higher-level plan sets no density target.

What is the difference between the floor area ratio and the building coverage ratio?

The floor area ratio limits the floor area; the building coverage ratio limits the building’s footprint on the ground. Both apply at the same time.

By when must municipalities adopt the new building terms?

At the latest by 29 February 2028. Until a municipality updates its own BZO, it continues to use the old terms.

Does the land potential check replace a building permit?

No. It is a first, non-binding reading from public sources – not a feasibility study and not a building permit.

For daughters and sons

You often see the unused potential in your parents’ garden more clearly than they do. Show them this overview first, not a decision already made. That way, your parents see that nobody is pushing them into a building project – and you remain the daughter or son who cares, not the person who decides.

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Which other steps fit your plot?

Sources

Planning and Building Act of the Canton of Zurich (PBG), sections 19, 30, 31, 45, 46, 48, 49a, 255–259 (LS 700.1), in German · full text read, Oct. 2026
PBG, transitional provisions on the amendment of 14 September 2015, para. 1 (deadline extended to 29 February 2028, Act of 26.1.2026), in German · Oct. 2026
ÖREB register of the Canton of Zurich (official geoportal), in German · retrieved Oct. 2026
Federal Supreme Court 1P.256/2006 E. 2.5; Cantonal Building Appeals Board (Baurekursgericht) ZH, BRGE I No. 0059/2020, in German · decision of 8 May 2020

Floor area ratio in Zurich: how much may you actually build?