Question
Given only a site outline, a ward-level address and the width of the front road, how far does Parti's regulation report confirm things automatically, and from where does it leave them declared or unevaluated? We record this on 5 hypothetical sites.
Method
- Product and screens: Parti, the Site tool and the Scheme tool.
- Hypothetical sites: 5 rectangles, 20 m east–west by 25 m north–south, drawn along the axes of the plane rectangular coordinate system (Zone IX) that Parti uses to compute area, each centred on a point in the table below. They are not the outlines of real parcels or buildings, and the address entered goes no further than the ward. The project names in the product also carry the word 「架空」 (hypothetical).
- Inputs: the rectangle's vertices were pasted as a GeoJSON Polygon into 「Boundary (GeoJSON Polygon)」. For the front road we declared a road of 6 m on the south side and 「道路なし」 (no road) on the north, east and west sides, so that all four sides are declared. 「Planned FAR %」 and 「Planned BCR %」 were left blank, and the address was not geocoded.
- Steps: 「Save site」, then 「Fetch constraints」; we recorded the constraints list and the regulation report. We then opened Scheme, pressed 「Generate from envelope」, opened the judgement block and the 「建築可能ボリューム (buildable envelope)」 block, and recorded the display.
- Changing the road width: on sites 2 and 3 (one in a residential-class zone, one in another class of zone) we rewrote only the width of the south road, to 4, 8, 12 m, pressed 「Save site」 and recorded the same displays. 「Fetch constraints」 was not pressed again. Last, we set the width back to 6 m and read the screens once more.
- Number of readings: 26, counting the Site screen and the Scheme screen separately.
- How the tables are written: where the product displays a long sentence, the tables carry its opening only: for the floor area ratio (
far_pct), up to the first full stop; for the Scheme judgement, up to where the explanation of the statutory provision begins. - Date and production revision: 2026-10-13. Cloud Run revision
parti-sha-a97414c(commita97414c). The revision was the same before and after the measurements. The results are the output of the production revision at that time.
How Parti behaves was confirmed by reading the code at that commit.
- Site area: the planar area in Zone IX, rounded to 0.1 m², with the provenance tag
derived. - Zoning lookup: runs only when 「Fetch constraints」 is pressed. The site boundary is overlaid on the zoning polygons and each polygon's share of the site area is computed; it is not a test of which polygon contains the centroid. The lookup returns 3 items: zoning, floor area ratio and building coverage ratio.
- Status of a regulation report row: one of
pass,fail,unevaluated,evaluated. - Tags in the constraints list: every row carries a provenance (
declared,fetched,derived) and, separately, a status (confirmed,unconfirmed); the screen prints both.unconfirmedis the status of a row whose value the product could not obtain. A failed fetch is recorded asunconfirmedwith an empty value and is not replaced by a default. In a lookup by site boundary, when no zoning polygon intersects the site the zoning, floor area ratio and building coverage ratio rows are allunconfirmed. With a single zoning district, the floor area ratio and building coverage ratio rows areunconfirmedwhen its polygon does not cover the whole site or when the value is missing, andconfirmedotherwise. Declared values and a site area that could be computed are recorded asconfirmed. For the rows in this note,confirmedis therefore a status inside the product saying that it obtained the value by lookup, declaration or calculation; it does not say that a third party has checked the value. - Floor area ratio and building coverage ratio rows: the user's planned value is compared with the limit. With the planned value blank the row is
unevaluated. - Floor area ratio limit from the front road width: evaluated only when all four sides are declared. The widest declared road is used; when it is narrower than 12 m, the limit is the smaller of the designated ratio and road width × coefficient. The coefficient is 0.4 in residential-class zones and 0.6 in the others.
- Rewriting of the floor area ratio row: the row is rewritten by the rule above after every lookup and every save of the site. Its provenance is
derivedwhile the rule is applied and the lookup's own provenance otherwise. The row's status is not rewritten. - Slant-plane, shadow and evacuation rows: always
unevaluatedin the regulation report. Slant planes are evaluated per scheme; shadow regulation and evacuation rules are not implemented at this stage. - Generate from envelope: the target number of floors is the integer part of (floor area ratio limit ÷ building coverage ratio limit), at least 1, with each floor 3.5 m high. The building coverage ratio is not applied to the floor shape and the total floor area is not cut down to the floor area ratio limit; an excess is shown as a warning.
Results
The sites entered.
| Site | Address as typed | Centre longitude | Centre latitude | South road width (m) |
|---|---|---|---|---|
| 1 | 東京都港区 (Minato-ku, Tokyo) | 139.7387 | 35.6298 | 6 |
| 2 | 東京都新宿区 (Shinjuku-ku, Tokyo) | 139.7175 | 35.6787 | 6 |
| 3 | 東京都千代田区 (Chiyoda-ku, Tokyo) | 139.75127 | 35.69609 | 6 |
| 4 | 東京都新宿区 (Shinjuku-ku, Tokyo) | 139.72219 | 35.70568 | 6 |
| 5 | 東京都中野区 (Nakano-ku, Tokyo) | 139.66560 | 35.70574 | 6 |
Values in the constraints list after 「Fetch constraints」.
| Site | Zoning (zoning) | Building coverage ratio (bcr_pct) | Floor area ratio (far_pct), opening of the displayed text | Site area |
|---|---|---|---|---|
| 1 | 準工業地域（quasi_industrial） | 60% | 360% ＝ min(指定 400%, 道路 360%) | 500 m² |
| 2 | 第二種中高層住居専用地域（mid_high_residential_2） | 60% | 200% ＝ min(指定 200%, 道路 240%) | 500 m² |
| 3 | 商業地域（commercial） | 80% | 360% ＝ min(指定 700%, 道路 360%) | 500 m² |
| 4 | 近隣商業地域（neighborhood_commercial） | 80% | 360% ＝ min(指定 400%, 道路 360%) | 500 m² |
| 5 | 商業地域（commercial） | 80% | 360% ＝ min(指定 600%, 道路 360%) | 500 m² |
Provenance tags of the constraints list, and the source line displayed under each value.
| Constraint (name as displayed) | Provenance tags | Source line as displayed | Sites |
|---|---|---|---|
| bcr_pct | FETCHED / CONFIRMED | 国土数値情報 A29 用途地域 — 令和元年度 (2019) | 5 |
| far_pct | DERIVED / CONFIRMED | 国土数値情報 A29 用途地域 — 令和元年度 (2019) | 5 |
| zoning | FETCHED / CONFIRMED | 国土数値情報 A29 用途地域 — 令和元年度 (2019) | 5 |
| road_frontages | DECLARED / CONFIRMED | (none displayed) | 5 |
| site_area_m2 | DERIVED / CONFIRMED | (none displayed) | 5 |
Status of each regulation report row.
| Row | Status | Explanation as displayed | Sites |
|---|---|---|---|
| 対象地域（平面直角座標系 第IX系） | PASS | 東京都（申告された住所）— 第IX系の区域内、EPSG:6677 の有効範囲内 (in the Zone IX area; areas computed) | 5 |
| 容積率 (FAR) | UNEVALUATED | no planned value declared | 5 |
| 建蔽率 (BCR) | UNEVALUATED | no planned value declared | 5 |
| 前面道路幅員による容積率制限（52条2項） | EVALUATED | differs by site | 5 |
| 斜線制限 | UNEVALUATED | 前面道路 北道路なし・東道路なし・南6m・西道路なし 申告済。斜線制限の適否（道路・隣地・北側）は各スキームの適合判定で階ごとに評価します。 | 5 |
| 日影規制 | UNEVALUATED | not implemented in this stage | 5 |
| 避難規定 | UNEVALUATED | not implemented in this stage | 5 |
| 住所と敷地境界の整合 | UNEVALUATED | requires both a confirmed geocoded point and a boundary | 5 |
Result of 「Generate from envelope」.
| Site | total floor area | Area by floor (from the ground up) | FAR judgement (opening of the displayed text) |
|---|---|---|---|
| 1 | 2640 m² | 1-2F 500 m² ×2; 3F 480 m²; 4F 433.3 m²; 5F 386.7 m²; 6F 340 m² | total floor area 2640.0 m² is 528.0% of the site area 500.0 m² — exceeds the FAR limit 360% by 168.0pp (840.0 m² over) |
| 2 | 1444 m² | 1-2F 500 m² ×2; 3F 444 m² | total floor area 1444.0 m² is 288.8% of the site area 500.0 m² — exceeds the FAR limit 200% by 88.8pp (444.0 m² over) |
| 3 | 1913.3 m² | 1-2F 500 m² ×2; 3F 480 m²; 4F 433.3 m² | total floor area 1913.3 m² is 382.7% of the site area 500.0 m² — exceeds the FAR limit 360% by 22.7pp (113.3 m² over) |
| 4 | 1913.3 m² | 1-2F 500 m² ×2; 3F 480 m²; 4F 433.3 m² | total floor area 1913.3 m² is 382.7% of the site area 500.0 m² — exceeds the FAR limit 360% by 22.7pp (113.3 m² over) |
| 5 | 1913.3 m² | 1-2F 500 m² ×2; 3F 480 m²; 4F 433.3 m² | total floor area 1913.3 m² is 382.7% of the site area 500.0 m² — exceeds the FAR limit 360% by 22.7pp (113.3 m² over) |
The 「建築可能ボリューム (buildable envelope)」 block on the same screen.
| Site | Zoning (zoning) | 「建築可能ボリューム (buildable envelope)」 as displayed |
|---|---|---|
| 1 | 準工業地域（quasi_industrial） | 道路斜線（南, 勾配1.5） / 隣地斜線（北・東・西, 勾配2.5） / 絶対高さ制限: なし（高度地区は本製品未保持） |
| 2 | 第二種中高層住居専用地域（mid_high_residential_2） | 道路斜線（南, 勾配1.25） / 隣地斜線（北・東・西, 勾配1.25） / 北側斜線（北, 立上り10m） / 絶対高さ制限: なし（高度地区は本製品未保持） |
| 3 | 商業地域（commercial） | 道路斜線（南, 勾配1.5） / 隣地斜線（北・東・西, 勾配2.5） / 絶対高さ制限: なし（高度地区は本製品未保持） |
| 4 | 近隣商業地域（neighborhood_commercial） | 道路斜線（南, 勾配1.5） / 隣地斜線（北・東・西, 勾配2.5） / 絶対高さ制限: なし（高度地区は本製品未保持） |
| 5 | 商業地域（commercial） | 道路斜線（南, 勾配1.5） / 隣地斜線（北・東・西, 勾配2.5） / 絶対高さ制限: なし（高度地区は本製品未保持） |
far_pct when only the width of the south road is changed.
| Site | South road width (m) | far_pct (opening of the displayed text) | Clause that follows | Provenance tags of far_pct |
|---|---|---|---|---|
| 2 | 4 | 160% ＝ min(指定 200%, 道路 160%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 2 | 6 | 200% ＝ min(指定 200%, 道路 240%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 2 | 8 | 200% ＝ min(指定 200%, 道路 320%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 2 | 12 | 200% | 52条2項 評価済・非拘束 | FETCHED / CONFIRMED |
| 3 | 4 | 240% ＝ min(指定 700%, 道路 240%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 3 | 6 | 360% ＝ min(指定 700%, 道路 360%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 3 | 8 | 480% ＝ min(指定 700%, 道路 480%) | 52条2項 適用 | DERIVED / CONFIRMED |
| 3 | 12 | 700% | 52条2項 評価済・非拘束 | FETCHED / CONFIRMED |
Result of 「Generate from envelope」 when only the width of the south road is changed.
| Site | South road width (m) | total floor area | Area by floor (from the ground up) | FAR judgement (opening of the displayed text) |
|---|---|---|---|---|
| 2 | 4 | 968 m² | 1F 500 m²; 2F 468 m² | total floor area 968.0 m² is 193.6% of the site area 500.0 m² — exceeds the FAR limit 160% by 33.6pp (168.0 m² over) |
| 2 | 6 | 1444 m² | 1-2F 500 m² ×2; 3F 444 m² | total floor area 1444.0 m² is 288.8% of the site area 500.0 m² — exceeds the FAR limit 200% by 88.8pp (444.0 m² over) |
| 2 | 8 | 1484 m² | 1-2F 500 m² ×2; 3F 484 m² | total floor area 1484.0 m² is 296.8% of the site area 500.0 m² — exceeds the FAR limit 200% by 96.8pp (484.0 m² over) |
| 2 | 12 | 1492 m² | 1-2F 500 m² ×2; 3F 492 m² | total floor area 1492.0 m² is 298.4% of the site area 500.0 m² — exceeds the FAR limit 200% by 98.4pp (492.0 m² over) |
| 3 | 4 | 1426.7 m² | 1F 500 m²; 2F 486.7 m²; 3F 440 m² | total floor area 1426.7 m² is 285.3% of the site area 500.0 m² — exceeds the FAR limit 240% by 45.3pp (226.7 m² over) |
| 3 | 6 | 1913.3 m² | 1-2F 500 m² ×2; 3F 480 m²; 4F 433.3 m² | total floor area 1913.3 m² is 382.7% of the site area 500.0 m² — exceeds the FAR limit 360% by 22.7pp (113.3 m² over) |
| 3 | 8 | 2780 m² | 1-3F 500 m² ×3; 4F 473.3 m²; 5F 426.7 m²; 6F 380 m² | total floor area 2780.0 m² is 556.0% of the site area 500.0 m² — exceeds the FAR limit 480% by 76.0pp (380.0 m² over) |
| 3 | 12 | 3740 m² | 1-5F 500 m² ×5; 6F 460 m²; 7F 413.3 m²; 8F 366.7 m² | total floor area 3740.0 m² is 748.0% of the site area 500.0 m² — exceeds the FAR limit 700% by 48.0pp (240.0 m² over) |
Reading the results
- Rows confirmed automatically: of the 8 rows of the regulation report, 1 was
PASS(「対象地域（平面直角座標系 第IX系）」) and 1 wasEVALUATED(「前面道路幅員による容積率制限（52条2項）」). The other 6 rows wereUNEVALUATED, and no row wasFAIL. This was the same on all 5 sites. - Rows left unevaluated: the floor area ratio and building coverage ratio rows displayed 「no planned value declared」, because no planned value was entered. The shadow regulation and evacuation rows displayed 「not implemented in this stage」, and the row on consistency between address and boundary displayed 「requires both a confirmed geocoded point and a boundary」. We did not geocode the address.
- Provenance tags: of the 5 items in the constraints list, zoning and building coverage ratio were displayed as fetched (
FETCHED), the front roads as declared (DECLARED) and the site area as computed (DERIVED). The floor area ratio (far_pct) was displayed asDERIVED. The status displayed wasCONFIRMEDon every row recorded. - Floor area ratio limit: on 4 of the 5 sites (sites 1, 3, 4, 5) road width × coefficient was smaller than the designated ratio, and
far_pcttook that value. On the remaining 1 (site 2) the designated ratio was the smaller one. - Generated result: all 5 sites displayed 「⚠ exceeds FAR」, and the total floor area was above the
far_pctlimit. This matches the behaviour described above: generation does not cut the total floor area down to the floor area ratio limit. For the building coverage ratio, every site displayed a note saying that the result is a starting point just after generation with the ground floor placed over the whole site. For slant planes, every site displayed 「全ての階が道路斜線制限内」 and 「全ての階が隣地斜線制限内」. - When the road width changes: after rewriting the width and pressing 「Save site」, the
far_pctdisplay changed without pressing 「Fetch constraints」 again. At 12 m the display read 「52条2項 評価済・非拘束」,far_pctequalled the designated ratio, and its provenance tags wereFETCHED / CONFIRMED. At the narrower widths they wereDERIVED / CONFIRMED. The generated total floor area also changed with the width. - When the width is set back: after setting the width back to 6 m, the displays read again were the same as in the first reading on both of the 2 sites.
- The sites here are hypothetical; these are not study results for real parcels or projects.
Limits
- This is a record of 5 hypothetical rectangles only. It does not cover other site shapes, other road conditions, or sites that span more than one zoning district.
- The width and position of the front road are values the author declared for the exercise; they have no relation to roads on the ground.
- For the release named by the screen's label, the National Land Numerical Information page for the zoning data says 「精緻な作業には使用しないでください」 (do not use it for precise work).
- The screen displays the source as 「国土数値情報 A29 用途地域 — 令和元年度 (2019)」; that text is a constant in the code. The zoning table has no column that records a file name or a release year. For that reason this note could not confirm, from the data itself, which release the production data is.
- According to the screen, the product does not hold height designations of height control districts or shadow regulation designations. Shadow regulation and evacuation rules are not evaluated by the product at the time of measurement.
- This note is a record of what the product displays, not a judgement of legal compliance for any particular site.
How to reproduce
- Sign in to Parti and create a project.
- In the Site tool, enter the address (to ward level), the site boundary as a GeoJSON Polygon and the front roads (a width on the south side, 「道路なし」 on the other three sides), then press 「Save site」.
- Press 「Fetch constraints」 and read the constraints list and the regulation report.
- Open the Scheme tool, press 「Generate from envelope」, open the judgement block and the 「建築可能ボリューム (buildable envelope)」 block, and read the display.
- To change the road width, rewrite the south width in the Site tool, press 「Save site」 and repeat the same steps.
Data attribution
- Zoning, floor area ratio and building coverage ratio: Source: National Land Numerical Information download site, Ministry of Land, Infrastructure, Transport and Tourism (https://nlftp.mlit.go.jp/ksj/). The values shown are 「国土数値情報（用途地域データ）」 (MLIT) as processed and displayed by Parti. The release year of the data is not stated here, for the reason given under Limits.
- Publication conditions for the zoning data are set per municipality. In the list MLIT publishes for the release named by the screen's label, the wards in this note (Minato-ku (港区), Shinjuku-ku (新宿区), Chiyoda-ku (千代田区), Nakano-ku (中野区)) are all listed as 「オープンデータ公開可」 (open data, publication permitted).
- The site outlines and coordinates are hypothetical inputs made by the author.
- How to use Parti: Parti documentation. Where the data used by DXA Labs products comes from: Data sources and measurements (Japanese).