§ 18

Building coverage percentage per BR18

Does project meet building percentage?

Answer: When you draw an extension or a new building, you must show that the building percentage holds. It's the floor area as a percentage of the plot area. Enter the plot area, total floor area (existing + new) and the area that under BR18's calculation rules is not counted. The calculator shows the building percentage and how much floor area building rights give room for.

Formula

Bebyggelsesprocent = medregnet etageareal ÷ grundens areal × 100

Medregnet etageareal = samlet etageareal − det areal, der efter BR18's beregningsregler ikke medregnes

Building coverage: 30% for detached single and two-family houses, 40% for dense low-rise, 60% for flats, 15% for summer houses and 45% for other buildings (BR18 chapter 8)

Symbols and units in the formula
Symbol	Meaning	Unit
grund_m2	Plot area (from the land register/cadastral map)	m²
etage_m2	Total floor area, existing + new	m²
fradrag_m2	Area not included (per BR18's calculation rules, e.g. carport/shed)	m²
maks_pct	Building type	%
=	Plot ratio (bebyggelsesprocent)	%
=	Largest floor area building regulations permit	m²
=	Etageareal tilbage (negativt = over)	m²
=	Counted floor area	m²

Validity and source

Source: Building Regulations BR18, chapter 8 Building coverage: 30% detached houses, 40% dense low-rise, 60% flats, 15% summer houses, 45% other

Does not apply when

Local plan and easements can set a lower percentage and that applies. Which areas don't count (basement, outbuildings and carports up to a certain size, loft rooms below a certain height) is in BR18's calculation rules. Look them up for the specific project. Height and distance requirements must also be met.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

Plot area (from the land register/cadastral map)800 m²
Total floor area, existing + new210 m²
Area not included (per BR18's calculation rules, e.g. carport/shed)30 m²
Building type30 %

Giver

Plot ratio (bebyggelsesprocent)22.5 %
Largest floor area building regulations permit240 m²
Etageareal tilbage (negativt = over)60 m²
Counted floor area180 m²

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Sådan bruger du den

Når du tegner en tilbygning, en carport med rum eller et nyt hus, skal du vise kommunen at bebyggelsesprocenten holder. Beregneren regner procenten ud fra grundareal og etageareal og viser hvor meget byggeretten giver plads til efter BR18 kapitel 8.

Step by step

Find grundens areal i tingbogen eller på matrikelkortet.
Læg etagearealet sammen for alle bygninger på grunden, eksisterende og nye.
Træk de arealer fra, der efter BR18's beregningsregler ikke tæller med.
Del med grundarealet, og gang med 100.
Sammenlign med byggeretten for bebyggelsestypen og med lokalplanen, hvis der er en.

Typical errors

At bruge bebygget areal i stedet for etageareal. Etagearealet tæller alle etager med.
At glemme lokalplanen. Den kan give en lavere procent, og den gælder så.
At trække arealer fra uden at tjekke BR18's beregningsregler. Kun de arealer, reglerne nævner, må trækkes fra.

Examples from everyday life

Tilbygning til et parcelhus

En familie vil udvide huset, så etagearealet bliver 210 m² på en grund på 800 m². Carport og udhus på i alt 30 m² tæller ikke med.

Plot area (from the land register/cadastral map): 800 m²
Total floor area, existing + new: 210 m²
Area not included (per BR18's calculation rules, e.g. carport/shed): 30 m²
Building type: Detached single and two-family houses (30%)

It means: Bebyggelsesprocenten bliver 22.5 %. Byggeretten giver 240 m², så der er 60 m² tilbage.

Rækkehus med ny førstesal

Et rækkehus på en grund på 250 m² skal have førstesal, så etagearealet bliver 120 m².

Plot area (from the land register/cadastral map): 250 m²
Total floor area, existing + new: 120 m²
Area not included (per BR18's calculation rules, e.g. carport/shed): 0 m²
Building type: Dense-low: terraced, chain and semi-detached houses (40%)

It means: Procenten bliver 48 %, og byggeretten er 100 m². Det tilbageværende areal giver -20 m², altså over grænsen, så projektet kræver dispensation eller en mindre førstesal.

Nyt sommerhus

Et sommerhus på 160 m² skal bygges på en grund på 1200 m² i et sommerhusområde.

Plot area (from the land register/cadastral map): 1,200 m²
Total floor area, existing + new: 160 m²
Area not included (per BR18's calculation rules, e.g. carport/shed): 0 m²
Building type: Holiday home in holiday home area (15%)

It means: Bebyggelsesprocenten er 13.3 %, og byggeretten giver 180 m². Der er 20 m² tilbage til fx et anneks.

Rule of thumb

På en parcelhusgrund på 1000 m² giver 30 % plads til 300 m² etageareal.

How to check the answer

Medregnet etageareal gange 100 og delt med grundarealet skal give procenten. Kommunens byggesagsbehandler regner det samme.