Why rooftop gardens cannot replace all required ground landscaping
When owners in Seoul rebuild a small mixed-use house or a neighborhood retail building, many assume that a large rooftop garden will satisfy the landscaping rule.
The Building Act Enforcement Decree, however, counts only two thirds of rooftop landscaping as site landscaping, and that counted area cannot exceed half of the required landscaping area.
Discovering this after signing a design contract can force a redesign of ground-floor parking and entrances, or lead to overpaying for a site that cannot fit the required landscaping.
This calculator applies the site-area and floor-area bands in Article 24 of the Seoul Metropolitan Government Building Ordinance to find the required landscaping area.
It then applies the two-thirds rooftop credit and the 50% cap to show how much landscaping must stay on the ground and how far your plan falls short.
It also shows Landscaping Standard references such as the half rate for grass-only roofs, the half rate and one-third cap for greenhouses and public pilotis, 10% natural ground and a 50% planting area.
ScopeThis calculator is based on Korean rules for 2026, checked on 2026-10-24 through the National Law Information OPEN API of the Ministry of Government Legislation.
It accepts reference dates from 2026-10-06, when the current decree took effect, to 2026-12-31, and assumes the rules stay unchanged after that.
Results are area arithmetic, not a building-permit determination, landscape design approval or rooftop structural assessment.
Four sets of information to prepare
Site area and total floor area
Use the legal site area under the Building Act.
If road setbacks or corner cuts remove part of the parcel, enter the area after that deduction so the requirement is not overstated.
Total floor area is the sum of all floors including basements, which differs from the FAR-counted area.
Planned landscaping
Split the plan into ground landscaping, its natural-ground part, rooftop trees/shrubs/facilities, rooftop grass or groundcover only, and greenhouse or public-pilotis landscaping.
A layout sketch or your architect’s draft area table gives the best inputs.
Location and applicability
Choose whether the site is in Seoul and whether it is a general building, a school-relocation site, or a factory, logistics, green-area, livestock, temporary or exempted building that needs special review.
If a district-unit plan or permit condition sets the rate, enter that confirmed rate manually.
Layout and planting references
Selecting the zoning district (residential, commercial or industrial) shows minimum tree and shrub counts for reference.
Also indicate whether a site of 2,000 m² or more faces a road at least 20 m wide, to check the street-side placement rule.
Areas accept up to two decimal places and numbers with comma separators.
Leave unknown values blank to keep the dependent result pending, and enter 0 only for an area you have confirmed is zero.
The form starts empty, and the fictional example buttons let you see the calculation flow first.
Landscaping rates under Seoul Building Ordinance Article 24
Building Act Article 42(1) requires an owner building on a site of 200 m² or more to provide landscaping according to the standards set by the local ordinance.
Article 24 of the Seoul Building Ordinance sets those standards by site area and total floor area.
The table shows the general bands the calculator applies automatically.
Landscaping rates by site and floor-area band under Seoul Building Ordinance Article 24| Site or building condition | Rate | 500 m² site | Basis |
|---|
| Site under 200 m² | Not covered | — | Building Act Article 42(1) |
| Site 200 m² to under 300 m² | 5% | — | Ordinance Article 24(3) |
| Total floor area under 1,000 m² | 5% | 25 m² | Ordinance Article 24(1)(3) |
| Total floor area 1,000 m² to under 2,000 m² | 10% | 50 m² | Ordinance Article 24(1)(2) |
| Total floor area 2,000 m² or more | 15% | 75 m² | Ordinance Article 24(1)(1) |
| Building on a school-relocation site | 30% | 150 m² | Ordinance Article 24(1)(5) |
Reading the thresholds
- A 199.99 m² site is outside the rule; coverage starts at 200 m²
- The floor-area bands apply from a 300 m² site
- Floor area of 999.99 m² is 5%, 1,000 m² is 10%, 1,999.99 m² is 10% and 2,000 m² is 15%
- Sites of 200 m² to under 300 m² stay at 5% even with a large floor area
A school-relocation site is a former school site defined in Article 45(2) of the Seoul Urban Planning Ordinance, such as a relocated or closed school, or land released from a school facility designation.
Do not apply 30% or downgrade to a general band without confirming that status.
Sites under 200 m² fall outside Act Article 42(1), but district-unit or redevelopment plans can set their own rules, so the calculator shows 0 m² with a warning to check.
Two-thirds rooftop credit and the 50% cap
Decree Article 27(3) provides that where rooftop landscaping follows the standard notified by the Minister of Land, Infrastructure and Transport, two thirds of the rooftop landscaping area may be counted as site landscaping.
The second sentence of the same paragraph states that the counted area may not exceed 50 percent of the landscaping area required under Act Article 42(1).
Because both rules apply together, extra rooftop area adds less and less and eventually adds nothing.
Step 1: two-thirds conversion
Converted rooftop = recognized rooftop area × 2/3
A recognized rooftop area of 40 m² converts to about 26.67 m².
One third never counts toward the requirement.
Step 2: 50% cap
Rooftop credit = min(converted rooftop, requirement × 50%)
With a 50 m² requirement the cap is 25 m².
About 1.67 m² of the 26.67 m² converted area is not counted.
Rooftop area that reaches the cap
The recognized rooftop area at which the credit hits the cap is requirement × 50% × 3/2, or 0.75 times the requirement.
For a 50 m² requirement the cap is reached at a recognized rooftop area of 37.5 m².
A larger rooftop garden may still help comfort and insulation, but it no longer helps meet the requirement.
Recognized rooftop area, the 2 m line and pilotis rules
Article 3 of the Landscaping Standard (MOLIT notice) defines rooftop landscaping as artificial-ground landscaping installed 2 m or more above grade, excluding flower boxes on balconies.
Article 12 sets how rooftop landscaping area is measured.
The calculator reflects these rules through separate input fields.
Counting rates and caps by landscaping location and planting type| Location or type | Counting rate | Cap or condition | Basis |
|---|
| Open space or outdoor area below 2 m | 100% | No cap | Seoul Ordinance Article 24(2)(1) |
| Rooftop trees, shrubs and facilities | 100% → ×2/3 | 50% of requirement | Standard Article 12, Decree Article 27(3) |
| Rooftop grass or groundcover only | 50% → ×2/3 | Exclude permanent shade under solar panels | Standard Article 12(1) |
| Greenhouse or public-passage pilotis | 50% | One third of the requirement | Seoul Ordinance Article 24(2)(2) |
Effective rate of a grass roof
A roof planted only with grass or groundcover is halved and then multiplied by two thirds, so only about one third of its actual area counts.
A 60 m² grass roof contributes about 20 m².
Adding shrub beds to the same roof changes the result.
Items not modeled
Wall greening counts at half of the covered area but may not exceed 10% of the planting area, a separate rule.
The rule that counts rooftop trees at 1.5 times their number concerns planting counts, not area.
The half credit for shared vegetable gardens in Seoul Ordinance Article 25(2) applies to landscape-facility area, so confirm it with your architect.
Even with a structure underneath, such as an underground car park, landscaping less than 2 m above grade counts in full as ground landscaping under the Seoul ordinance.
That artificial ground is not natural ground, however, so it does not count toward the 10% natural-ground rule below.
The greenhouse and pilotis credit is a Seoul ordinance rule, so the calculator does not apply it when you choose a location outside Seoul.
Formulas for required ground area and shortfall
- Required landscaping A = site area × rate / 100
- Recognized rooftop area R = rooftop trees, shrubs and facilities + rooftop grass or groundcover × 1/2
- Rooftop credit = min(R × 2/3, A × 50%)
- Pilotis and greenhouse credit = min(pilotis and greenhouse area × 1/2, A × 1/3)
- Ground area required = max(A − rooftop credit − pilotis and greenhouse credit, 0)
- Ground shortfall = max(ground area required − planned ground landscaping, 0)
- Overcount = simple sum of planned areas − area counted toward the requirement
Comparisons use unrounded values, and the screen shows two decimal places.
The requirement is also shown in pyeong, using the same 3.3058 m² per pyeong as other real estate calculators on this site.
If planned ground landscaping meets the required ground area, the starred card shows the surplus; otherwise it shows the shortfall.
The overcount shows how much smaller the counted area is than the simple total of everything you planned.
It combines the one-third rooftop reduction, the 50% cap, the half rate for grass roofs and the half rate for pilotis.
The larger it is, the more likely an early design review will be misunderstood.
Fictional examples of a ground shortfall
Landscaping calculation for a fictional small mixed-use building and a mid-size retail building| Item | Small mixed-use | Mid-size retail |
|---|
| Site / total floor area | 500 m² / 1,500 m² | 1,200 m² / 4,800 m² |
| Rate / required landscaping | 10% / 50 m² | 15% / 180 m² |
| Rooftop trees/shrubs + grass only | 30 m² + 20 m² | 120 m² + 40 m² |
| Recognized rooftop → two-thirds | 40 m² → 26.67 m² | 140 m² → 93.33 m² |
| Rooftop credit (50% cap) | 25 m² | 90 m² |
| Public pilotis → credit | 0 m² | 30 m² → 15 m² |
| ★ Ground area required | 25 m² | 75 m² |
| Planned ground / shortfall | 18 m² / 7 m² | 70 m² / 5 m² |
| Simple sum / counted / overcount | 68 / 43 / 25 m² | 260 / 175 / 85 m² |
In the small example the planned areas add up to 68 m², which seems to exceed the 50 m² requirement.
The roof counts only up to 25 m², however, so 18 m² of ground landscaping is 7 m² (about 2.12 pyeong) short.
A larger roof would not reduce the shortfall because of the cap; the ground-floor planters or parking layout must change instead.
In the mid-size example, 30 m² of public pilotis counts as 15 m², lowering the required ground area to 75 m², which is still 5 m² more than the planned 70 m².
Both examples are fictional and are not confirmed facts about any real site.
After loading an example, the review keeps that provenance even if you edit the numbers.
Factories, green areas, exemptions and manual rates
The proviso to Act Article 42(1) and Decree Article 27 identify buildings that need no landscaping and buildings with separate standards.
This calculator never approves an exception or relaxation automatically.
If any item below may apply, choose special review and enter the rate confirmed with the authority or your architect.
May skip landscaping under Decree Article 27(1)
- Buildings in green areas
- Factories on sites under 5,000 m², factories under 1,500 m² of floor area, factories in industrial complexes
- Livestock buildings and temporary buildings
- Logistics facilities under 1,500 m² (except in residential or commercial areas)
- Buildings in natural-environment conservation, agricultural-forest or management areas (except district-unit plan zones)
Exempt under Seoul Ordinance Article 24(4)
- Traditional markets designated and announced by the district mayor
- Correctional and military facilities, parking-only buildings
- Public bus depots, passenger and freight terminals, wholesale agricultural markets
- Schools (limited to no less than half of the landscaping standard)
Decree Article 27(2) sets 10% for factories and logistics facilities with 2,000 m² or more of floor area, 5% for 1,500 m² to under 2,000 m², and 10% for airport facilities and railway stations.
District-unit plans, redevelopment plans, special building zones and building-committee conditions may also require different rates.
Outside Seoul, enter the rate from the local city or county building ordinance and the nationwide two-thirds and 50% rooftop rules still apply.
Natural ground 10%, planting area 50% and planting counts
Meeting the area requirement is not the end of the review, because layout and planting rules also apply.
Landscaping Standard Article 4 requires a planting area of at least 50% of the required landscaping area, each planting bed at least 1 m on a side and 1 m², and each facility space at least 10 m².
Article 5(1) requires at least 10% of the required area to be natural ground, and Article 5(3) requires sites of 2,000 m² or more facing a road 20 m or wider to place at least 20% along the street.
Minimum planting counts per square meter by zoning district under Standard Article 7 with a 50 square meter example| Zoning district | Trees per m² | Shrubs per m² | Trees for 50 m² | Shrubs for 50 m² |
|---|
| Commercial | 0.1 | 1.0 | 5 | 50 |
| Residential | 0.2 | 1.0 | 10 | 50 |
| Industrial | 0.3 | 1.0 | 15 | 50 |
Minimum soil depth by planting type for rooftop and artificial ground under Standard Article 15| Planting type | Natural soil depth | Artificial soil depth |
|---|
| Herbaceous plants and groundcover | 15 cm | 10 cm |
| Small shrubs | 30 cm | 20 cm |
| Large shrubs | 45 cm | 30 cm |
| Trees | 70 cm | 60 cm |
Soil depth excludes the drainage layer, and soil weight bears directly on the roof structure.
Standard Article 14 requires an architect or structural engineer to confirm safety when landscaping is added to an existing roof, and Article 18 requires railings of at least 1.2 m and other safety structures.
The calculator does not recommend structures or species, and the counts are minimum references based on the required area.
Step-by-step use before hiring a designer, and scenarios
- Check the land-use plan and cadastral map for the Seoul location, zoning and any district-unit plan, then enter the reference date
- Enter the post-setback site area and the total floor area including basements to see the rate and requirement
- Enter ground, natural ground, rooftop trees and shrubs, rooftop grass and pilotis areas separately, and check whether the rooftop cap is reached
- If there is a ground shortfall, enter an alternative ground-floor parking, entrance or planter layout and compare
- Save or print the TXT review and ask your architect and the authority to confirm it with the checklist
Rebuilding an old house as a mixed-use building
Shortfalls appear most often when the ground floor is filled with parking and shops and a roof garden is expected to cover landscaping.
Reserving ground space for at least half of the requirement first reduces redesign costs and delays.
Feasibility check before buying land
On the same site, moving from the 10% band to 15% increases the required ground area.
Entering a target floor area and a ground-floor layout shows in advance how much ground-floor space landscaping will take.
Tips and cautions
- If your floor area sits just above 1,000 m² or 2,000 m², compare whether a small change moves the rate band
- Treat rooftop gardens beyond the cap-reaching area as insulation or amenity space, not as landscaping credit
- A grass-only roof counts at about one third of its area, so consider adding shrub beds
- Record the document, date and officer in the memo; site details you enter are not sent in analytics events
Frequently asked questions
If I landscape the whole roof, can I skip ground landscaping?
No.
Building Act Enforcement Decree Article 27(3) counts only two thirds of rooftop landscaping as site landscaping, and the counted area cannot exceed 50 percent of the required landscaping area.
Unless greenhouse or public-pilotis credit applies, at least half of the requirement must be on the ground (open space or outdoor areas less than 2 m above grade).
Does a grass-only roof count at its full area?
Landscaping Standard Article 12 counts rooftop areas planted only with herbaceous plants or groundcover at one half.
The decree two-thirds factor then applies again, so a 30 m² grass-only roof contributes about 10 m² toward the requirement.
Areas with trees, shrubs or landscape facilities count at their actual area.
Does total floor area include basements and other buildings?
The bands in Seoul Ordinance Article 24(1) use the total floor area of the buildings.
Floor area is the sum of all floor areas, so basements are included, unlike the FAR-counted area.
If several buildings share the site, confirm the combined total with your architect.
My site is 250 m² but the floor area exceeds 2,000 m². Is the rate 15%?
Seoul Ordinance Article 24(3) sets 5% for sites of 200 m² or more but under 300 m², notwithstanding paragraph 1 and Decree Article 27(2)(4).
A 250 m² site therefore needs 5%, or 12.5 m², regardless of floor area.
Check whether a district-unit plan sets a different rule.
Do planters under ground-floor pilotis count?
Seoul Ordinance Article 24(2)(2) counts landscaping in pilotis used exclusively for public passage, and in greenhouses, at one half, up to one third of the landscaping requirement.
Pilotis used for parking rather than public passage need confirmation from the permitting authority before you rely on this credit.
Is a garden over an underground car park rooftop landscaping?
Landscaping Standard Article 3 defines rooftop landscaping as artificial-ground landscaping 2 m or more above grade.
Seoul Ordinance Article 24(2)(1) counts landscaping in open space or outdoor areas less than 2 m above grade in full.
Because a structure lies beneath, it does not count toward the 10% natural-ground rule in Standard Article 5.
Do factories and livestock buildings use the same rates?
Decree Article 27(1) lets buildings in green areas, factories on sites under 5,000 m², livestock buildings and temporary buildings skip landscaping, and Article 27(2) sets separate factory and logistics rates.
Seoul Ordinance Article 24(4) lists further exemptions.
This calculator never approves exceptions automatically, so choose the special-review option and enter the confirmed rate.
If the result says the requirement is met, is my permit safe?
The result is arithmetic on the areas you entered.
Planting counts and sizes, natural ground, street-side placement, rooftop structure, soil depth, waterproofing, district plans and building-committee conditions are reviewed separately.
Save the review and confirm it with your architect and the authority before finalizing the design.
Official sources, update policy and next steps
Statutes, local ordinances and administrative rules were searched and read directly through the National Law Information OPEN API.
The Building Act (ID 001823, MST 273437) took effect on 2026-02-27, and the Enforcement Decree (ID 002118, MST 290833) was promulgated and took effect on 2026-10-06; both are marked current.
The Seoul Building Ordinance (MST 2116749) is No. 10083 of 2026-03-30, the Seoul Urban Planning Ordinance (MST 2149501) is No. 10139 of 2026-07-13, and the Landscaping Standard is MOLIT notice 2021-1778, effective 2022-01-07.
- Building Act Article 42: landscaping duty on sites of 200 m² or more and delegation to ordinances
- Enforcement Decree Article 27: exempt buildings, separate factory rates, rooftop two-thirds and 50% cap
- Seoul Building Ordinance Articles 24 and 25: rates, below-2 m counting, greenhouses and pilotis, exemptions
- Landscaping Standard Articles 3, 4, 5, 7, 12 and 15: rooftop definition, planting, natural ground, street placement, rooftop area and soil depth
Rates and counting factors are rechecked immediately after any amendment to the ordinance, decree or notice, and otherwise once a year.
For an individual site, district-unit plans, permit conditions and building-committee decisions may take precedence, so recheck the latest practice right before signing a design contract.
Enter your site area and planned landscaping now to find the ground shortfall, then save the review for your architect and layout revisions.