archiSubdivision

Overview

What it does

archiSubdivision is a subdivision test-fit for a site. Place it, drag its corners onto your site boundary, and it lays out roads and plots: how many plots fit, how big they are, how much of the site goes to roads and how much stays open. Change the site, the plot sizes or the roads and the layout redraws.

• Ring roads that follow the site (the default): a row of plots all round the boundary, a ring road inside it, then two rows back to back and another ring while the site is deep enough. The roads bend with an L, a U, a T, a skewed or a many-sided site, with rounded bends.
• Plots between a minimum and a maximum area, each row split into plots of equal area with a minimum frontage; any plot can be resized in the plan.
• Entrance roads from outside (up to 3), cross roads between the rings on large sites, and link roads wherever a ring would otherwise be cut off — circulation always connects.
• Zones kept free: a pond the ring road goes round, an easement the roads may cross, a protected tree.
• The numbers: plots, their areas, roads, open space, net/gross and buildable area, and in 3D the plots, roads and building volumes.

A second layout, along the street, lays rows of plots parallel to one street edge with access and connector roads (see Along the street).

Getting started

Quick start

1. Load the library. In Archicad, open File › Libraries and Objects › Library Manager and add ArchiTools_Library_AC29.lcf (or _AC28). You can use the single archiSubdivision_AC29.gsm instead, but not both: they are the same object.
2. Place it. Pick the Object tool, open Site Planning › archiSubdivision and click once in the plan. A new object starts as a 120 × 100 m site with ring roads and one entrance.
3. Fit it to your site. Select the object and drag each corner onto your site boundary; the layout follows while you drag. Add corners with Corners on Site & Setbacks; drop a corner on its neighbour to remove it.
4. Set the plots. On Plots & Roads, set the plot depth, the smallest and largest plot area and the smallest frontage, then the road width and the bend radius.
5. Place the entrances. On Roads, pick how many and on which edges; then drag their ends in the plan. Large sites get cross roads between the rings.
6. Read the result. The info block in the plan and the Result box on Plots & Roads give the plots, the areas and the shares of the site.

Geometry

The site

The site is a polygon of 3 to 24 corners, edited in the plan. Clockwise and counter-clockwise outlines both work.

• Drag a corner anywhere; the layout follows the hotspot while you drag.
• Remove a corner by dropping it on one of its neighbours; its two edges become one.
• Add corners with Corners on Site & Setbacks: more corners split the longest edges, fewer drop the last ones.
• Entrance roads and the street edge follow their edges when corners are added or removed.
• A boundary that crosses itself draws no layout; the info block says so until the corners are untangled.

Layout

Ring roads

Every line of the layout is the site boundary moved inwards by a depth, so the roads follow the shape of the site: they turn with every corner, stop in a wing too narrow for them, and split in two where the site narrows to a waist. From the boundary in:

• A row of plots on the boundary, one plot deep (30 m by default), fronting ring road 1.
• Ring road 1, a road reserve 10 m wide by default (carriageway and footways).
• Two rows of plots back to back: the outer row fronts ring road 1, the inner row ring road 2.
• Ring road 2, and so on, up to Ring roads (at most) (3 by default). A ring road is laid while the site reaches past it.
• The plots fronting the last ring road from inside are as deep as the site allows; what lies deeper is open space — a green in the middle.

Layout

Plots and their sizes

Each site edge's stretch of a row is split into plots of equal area, as many as keep that area between Area at least and Area at most (400 and 700 m² by default, as near their middle as the stretch allows) and the frontage at least Frontage at least (15 m).

• Corner plots keep the minimum frontage on the road and take the corner of the site, so they come out larger than the others in their row.
• A plot only counts a road as its frontage where the road is really there: a stretch of a row that never reaches its road, or one too shallow for plots (less than A cut plot keeps of the row's depth), stays open space.
• Resize a plot by hand: tick Frontage hotspots in the plan on Roads and drag the end of a plot's frontage. That plot keeps the frontage you dropped; the others of its row share the rest by equal area, and if that would leave them under the minimum area, the row gives up one of them. Plot numbers elsewhere do not change. Reset plot sizes puts them all back.
• Building lines: the buildable area of every plot is the plot less the setbacks from its front, sides and rear (5, 3 and 5 m), dashed in the plan and a volume in 3D.

Circulation

Entrance, link and cross roads

• Entrance roads (0 to 3, on Roads) start on the edge you pick and run to the middle of the innermost ring road, crossing the rings on the way. Each has two hotspots: drag the outer end along its edge and the inner end sideways, and the road slants. Both at the same value, it runs straight in. An entrance whose inner end points away from the ring turns to the nearest point of it, so it never ends among the plots. An arrow outside each entrance points in.
• Link roads are added on their own: a ring road no entrance reaches — the second pocket of a waisted site, or the ring round a pond — is joined to the ring outside it (or to the boundary) from the middle of its longest side.
• Cross roads join each ring road to the next on large sites, across the two rows of plots between them, square to the site edge and spread evenly along each stretch. Set them Every so many metres (150 m for a new object), Every so many plots, or None. Each has a hotspot: drag it along its stretch (it cannot leave it).
• The plots on both sides of every entrance, link and cross road re-fit round it: none fronts across a road, and one it cuts keeps the side its front is on.

Geometry

Bends and junctions

• Bends: every corner of a ring road is rounded, both edges with concentric arcs — Bend radius on the centre line (15 m by default) plus and minus half the road width, as far as half of each neighbouring side allows. 0 gives sharp corners. The plots on either side follow the arcs: they take the corner a road gives up and give up the corner it takes, so the areas still add up.
• Junctions: where an entrance, link or cross road meets a ring road, the plot corners there are rounded with Junction radius (6 m; 0 = sharp), a kerb return. The road takes the pieces, and the road edges stop where the arcs start.

Constraints

Zones kept free

On Zones, up to 8 parts of the site with no plots: a pond, a protected tree, an easement, a no-go area. Each is an area (3 to 8 corners), a corridor along a line (2 to 8 points and a width) or a circle (a centre and a radius). Zones sets how many; Zone to edit picks one to change its kind, corners and width; Remove this zone deletes it. In the plan, drag every corner, a corridor's width, a circle's radius, and the centre of an area or a corridor to move the whole zone. Each zone keeps out:

• Plots (roads may cross it, as under a power line): no plot stands in it; the rows re-fit round it. Plots kept this far off adds a buffer.
• Plots and roads (the default for a new zone): the zone becomes a hole in the site, and the layout starts from it as from the boundary — a row of plots backing onto it, its own ring road round it, and a link road to the other rings, the way a lake gets waterfront lots. It must lie inside the site, clear of the other such zones; one that crosses the boundary or another keeps only plots out, with a warning.

Second layout

Along the street

With Layout set to Along the street, one site edge is the street (Street edge on Site & Setbacks), and the plots are laid in rows parallel to it:

• Row 0: plots fronting the street, one plot deep.
• Access roads (up to 5), each a plot depth behind the row before it, with a row of plots on either side.
• Connector roads (0 to 2) from the street to the last access road; drag them along the street.
• Each row is split into equal plots at least Frontage wide; a plot the boundary cuts is kept when it holds at least A cut plot keeps of a full plot. Zones keep the plots out here too (the roads stay straight).

Output

What it draws

• Plan: fills for the open space, the roads and the plots; the plot lines; the road edges, open where roads join; dashed centre lines and building lines; plot numbers and areas; entrance arrows and labels; the zones hatched and numbered; the info block. While a hotspot is dragged only the lines are drawn and the layout follows live.
• 3D: the site as open space, the roads and the plots a few centimetres over it, and on request the buildable volumes (a massing study).

Output

The info block

The block in the plan (and the Result box on Plots & Roads) gives:

• the layout: ring roads, road width, plot depth and the area limits;
• the plots — on the boundary and inside — the ring roads, entrances, link and cross roads;
• the plot area and its share of the site (net/gross), the average, smallest and largest plot;
• the road area and the open space, with their shares; the buildable area and the site area;
• a warning when something does not fit.

A new object puts the block under the site; after that it stays where you drop it, whatever the corners do.

Worked examples

Scenarios

Each plan is the layout the object computes for the settings listed; anything not listed is left at its default (ring roads 10 m wide with 15 m bends, plots 30 m deep of 400 to 700 m² with 15 m of frontage, 6 m junctions). The scale bar is 10, 50 or 100 m.

Default

As placed

A new object: a 120 × 100 m site, one ring road with plots round it and one entrance. The middle is too shallow for plots inside the ring, so it stays open.

Setting	Value
Site	rectangle, 120 × 100 m
Settings	none changed

• 10 plots, 451–1 243 m²
• 80.4 % net/gross
• 13.7 % roads

Ring roads

A rectangle, one entrance

200 × 160 m: plots on the boundary, one ring road, and plots fronting it from inside round a small green. The entrance splits the bottom row, and the corners where it meets the ring are rounded.

Setting	Value
Site	rectangle, 200 × 160 m
Roads	1 entrance, edge 1, at 100 m

• 45 plots, 472–943 m²
• 82.3 % net/gross
• 13.9 % roads
• 1 200 m² open

Ring roads

An L

The ring road turns both corners of the L. Its legs are too narrow for plots inside the ring at 30 m depth, so the inside stays green — shallower plots would fill it.

Setting	Value
Site	L of 6 corners, 240 × 220 m, legs 100 and 110 m wide
Plots & Roads	Frontage at least 12 m
Roads	2 entrances, on edges 1 and 5

• 43 plots
• 64.0 % net/gross
• 17.8 % roads

Cross roads

Two rings and cross roads

400 × 300 m holds two ring roads. Cross roads every 100 m join them across the double rows on the long sides; one entrance runs slanted (its inner end moved along).

Setting	Value
Site	rectangle, 400 × 300 m
Roads	2 entrances (edge 1 at 200 m; edge 3, outer end 120 m, inner end 160 m) · Cross roads every 100 m

• 179 plots
• 82.3 % net/gross
• 2 ring roads, 2 cross roads

Large site

A large skewed site

A 24 ha pentagon takes three ring roads, each following the site's slanted edges with rounded bends, and seven cross roads every 120 m.

Setting	Value
Site	pentagon, 600 × 500 m, 23.7 ha
Roads	2 entrances, on edges 1 and 4 · Cross roads every 120 m

• 342 plots, 474–883 m²
• 81.5 % net/gross
• 17.0 % roads
• 3 rings, 7 cross roads

Link road

A waisted site

Two pockets joined by a neck as narrow as two plots: the ring splits in two. The entrance reaches the left pocket; the right one gets a link road out to the boundary. The neck has no road, so it stays open.

Setting	Value
Site	12 corners, two 160 × 160 m pockets, a 70 × 60 m neck
Roads	1 entrance, edge 1, at 80 m

• 70 plots
• 74.5 % net/gross
• 1 link road

Zones

A pond, an easement and a tree

The pond keeps plots and roads out: it gets a row of plots backing onto it, its own ring road and a link road. The easement corridor and the protected tree keep only plots out — the ring road crosses the easement.

Setting	Value
Site	rectangle, 400 × 300 m
Zones	1: area 110 × 90 m, plots and roads · 2: corridor 20 m wide, plots · 3: circle, radius 18 m, plots
Roads	2 entrances, on edges 1 and 4

• 119 plots
• 55.4 % net/gross
• 1 link road

Bends

Sharp bends and a slanted entrance

The rectangle above with Bend radius and Junction radius at 0, and the entrance's inner end moved 40 m along: the road slants and the plots on both sides re-fit.

Setting	Value
Plots & Roads	Bend radius 0
Roads	Entrance 1: outer end 100 m, inner end 140 m · Junction radius 0

• 43 plots
• 80.7 % net/gross
• 15.2 % roads

Plot sizes

Bigger plots, one set by hand

Plots 35 m deep of 600 to 900 m²; the third plot dragged to 45 m of frontage. The plots inside the ring now fill the middle.

Setting	Value
Plots & Roads	Depth 35 m · Area at least 600, at most 900 m²
In the plan	Plot 3's frontage dragged to 45 m

• 36 plots
• 87.2 % net/gross
• 0 m² open

Along the street

Along the street

The other layout on the default site: a row on the street (bottom edge), an access road with a row on either side, and one connector road from the street.

Setting	Value
Plots & Roads	Layout Along the street

• 20 plots, 450–550 m²
• 85.0 % net/gross
• 15.0 % roads

Along the street

Along the street, skewed

A skewed quad with three access roads and two connectors; the boundary cuts the plots on the slanted sides, and a cut plot is kept when it holds at least half a full plot.

Setting	Value
Site	skewed quad, about 170 × 140 m
Plots & Roads	Layout Along the street · Access roads 3 · Connector roads 2, at 40 and 110 m

• 26 plots
• 66.7 % net/gross
• 15.0 % roads

In the plan

Editing in the plan

History

Versions