Type: area categories
The land use ordinance organises type of use into area categories. Each has its own catalogue of what is generally permissible and what is exceptionally permissible.
The system covers among others small settlement areas, purely and generally residential areas, special residential areas, village areas, mixed areas, urban areas, core areas, commercial areas, industrial areas and special areas. Each area category carries its own catalogue of permissible uses.
Two points matter for application.
| Point | What follows |
|---|---|
| The catalogues are graded | within an area category some uses are generally permissible and others only by way of exception |
| They apply without a local plan too | where the surroundings in an unplanned built-up area correspond to one of the categories, permissibility follows its catalogue |
A catch-all rule is added. Even a use generally permissible within a category may be impermissible where, by number, position, scale or purpose, it contradicts the character of the area.
Extent: four quantities
The extent of development is determined by four quantities, which may be set individually or in combination. Three of them govern building construction.
| Quantity | What it governs |
|---|---|
| Site coverage ratio | how much of the plot may be built over |
| Floor space ratio | how much floor space may be created in total |
| Building mass ratio | what building volume is permissible |
| Number of full storeys and height | how high building may go |
| Quantity | What it states | What it limits |
|---|---|---|
| The site coverage ratio | what proportion of the plot may be covered by structures | the footprint on the plot |
| The floor space ratio | how much floor space is permissible per square metre of plot | the total amount of floor space |
| The building mass ratio | used mainly in commercial and industrial areas | the volume, where room heights vary greatly |
The permissible maxima are set in the ordinance and differ by area category. They are to be taken from the ordinance text; the local plan may set its own figures within that framework.
What counts towards the site coverage ratio
One point regularly produces over-optimistic results in early feasibility work. It concerns the areas arising beside the building itself.
The areas of certain ancillary installations are in principle counted towards the permissible built area, including garages and parking with their access, and ancillary installations within the meaning of the ordinance. The ordinance provides for increased coverage up to specified limits.
Anyone counting only the building envelope overstates the achievable area. On-plot access areas belong in the assessment.
Building form and the developable area
Alongside type and extent, a local plan regularly sets two further quantities. Both concern the position of the building on the plot.
| Quantity | What it governs |
|---|---|
| Building form | detached or attached development; in detached form, buildings stand with a side distance to the boundary |
| The developable plot area | set by building lines, building limits or development depths; it determines where on the plot building may occur |
Both are also features of fitting in within unplanned built-up areas, where they must be derived from the existing surroundings. They therefore apply where no local plan exists.
The relationship to separation distances
Two levels of regulation independently limit what can be built on a plot. Both must be met, and the stricter prevails.
| Level | Field of law | Competence |
|---|---|---|
| The extent of development | planning law | federal |
| Separation distances | building regulations law | state |
Both must be observed, and the stricter governs. A design exhausting the floor space ratio may fail on separation distances, and vice versa.
For feasibility work it follows that both levels must be examined together. The article on separation distances covers the second level.
Why these figures matter for cost work
The relationship is frequently skipped in early assessments and is the most important point of this article. It links planning law to the reference quantity of every benchmark.
| Finding | What follows |
|---|---|
| Every cost benchmark needs a reference quantity | cost per square metre of gross floor area presupposes that this area is settled at all |
| Floor space ratio and gross floor area are not the same | floor space is determined under the rules of the land use ordinance, gross floor area under those of the relevant standard |
The system of reference quantities is covered in the article on gross and net floor area within the cost planning subject. It also sets out which areas enter the gross floor area.
Permissible density determines the economics of the site. At the same land price, the floor space ratio determines the price per achievable square metre. That is the central quantity in any site appraisal.
Related articles
This article reflects the position of the rules at the date of checking and serves professional orientation. It does not constitute legal advice and does not replace assessment of the individual case.