The constraints and opportunities plan

You now have nine lessons’ worth of findings about your block, and they are scattered. A base plan in one file. Spot levels in a notebook. Photographs of a soil hole. A Before You Dig response pack as a PDF. A spreadsheet of every plant with a keep-or-kill verdict against it.

Nobody can design from that, including you in three weeks’ time.

This lesson turns all of it into one drawing. In practice it is the last thing that happens in site analysis and the first thing that gets opened in concept design, and the quality of everything downstream is limited by how honest it is.

What a professional actually does here

In a landscape architecture practice this drawing is a numbered, issued, billable deliverable. It goes to the client before a single design idea is shown, and it exists for four reasons.

It converts findings into spatial facts. “The soil is sand over limestone at 400 mm” is a note. A hatched zone across the northern third of the block reading limestone at 400 mm — excavation cost, restricted rooting depth is something you can design around, because it has a location.

It surfaces the collisions early. The moment everything is on one sheet, the conflicts appear: the only level, sunny, sheltered corner is directly over the sewer junction. The tree you want to keep sits where the machinery has to come through. Finding that on paper costs an afternoon. Finding it mid-build costs thousands.

It is the document you argue from. When the client wants a pool on the west boundary and the drawing shows the setback, the drainage low point and the neighbour’s overlooking window, the conversation is about facts rather than taste.

It records what was known. If a constraint is on the drawing and the client chose to proceed anyway, that is documented. This is not paranoia; it is the difference between a professional practice and a bloke with a bobcat.

The framing that matters most: constraints are not obstacles, they are the other half of the brief. A design that appears to fit its site effortlessly is almost always one where every constraint was known before the pen moved.

What goes on it, and where it comes from

Layer	Source lesson
Boundaries, buildings, existing hard surfaces, dimensions	Measuring up
Spot levels, falls, high and low points, datum	Levels, falls and datum
Soil type, depth to limestone, coffee rock or clay	Perth soils and soil testing
Sun arcs, shade at 15:00 in January, hot west walls, sea breeze	Sun, shade and aspect
Downpipes, soakwells, surface flow, the puddle that never dries	Water on site
Sewer, water, power, gas, existing retic, easements	Locating services
Keep / kill / salvage verdicts on plants and structures	Auditing an existing garden
Tree protection zones and retained trees	Tree assessment

If a row is blank, go back and fill it. A constraints plan with a hole in it is worse than none, because you will design straight into the hole.

How to draw it

Work in overlays, then flatten

Print your base plan at 1:100 — several copies, and never draw on the original. Then build it up in layers on tracing paper or as separate layers in whatever software you are using, roughly four:

1. Legal and services — boundaries, setbacks, easements, sewer, water, power, gas, retic.
2. Environment — sun and shade, wind, water movement, soil zones.
3. Existing garden — retained plants, tree protection zones, surfaces to keep, structures to demolish.
4. Operations — access routes, stockpile areas, spoil, crossover.

Then flatten to one sheet. The flattening is where the thinking happens, because that is where you find out which layers collide.

Use a consistent graphic language

Convention	Meaning
Red	Constraint
Green	Opportunity
Orange or a “?” flag	Assumed, not yet verified
Solid line	Absolute — cannot move
Dashed line	Negotiable, or subject to approval
Hatched area	A zone, not a line
Arrow	Direction — wind, view, fall, access

The hatching rule is the one people get wrong. A tree protection zone, a sewer clearance, afternoon shade and a drainage low point are all areas. Drawn as lines they invite you to design right up to them.

Every version gets a north arrow, a scale, and a date. Site analysis has a shelf life — a neighbour builds a two-storey and your shade drawing is wrong.

Annotate with facts, not adjectives

“Hot” is useless. “West-facing rendered wall, 2.4 m, in full sun from 13:00, still radiating at 19:00 in February” tells the designer to plant a deciduous screen, build a pergola, or move the seating.

Every annotation should carry a number, a time, a direction or a depth. If it carries none of those, you have written an opinion.

The WA layers people forget

Generic site analysis advice will not prompt you for these. On a Perth block they are often the expensive ones.

• Depth to limestone or coffee rock, drawn as a zone. It sets your excavation method, your machinery, your drainage and your tree choices.
• Side access, measured at the pinch point. Not the gate width — the narrowest point between the house and the fence, usually where the meter box or the aircon condenser sits. Note overhead clearance too (eaves, the service line to the house). This single number decides bobcat versus wheelbarrow, and it is a multiplier on your labour cost in Phase 7.
• The verge and crossover. Where materials can be stockpiled, where a truck can stand, and whether there is a council street tree with its own protection requirements.
• The Fremantle Doctor. The afternoon south-westerly is an opportunity, and a solid 1.8 m screen on your south-west boundary throws it away. Draw it as an arrow, in green.
• Winter sun into the house. The northern aspect is the one asset you cannot buy. Mark where winter sun reaches the living areas and do not plant an evergreen in it.
• Bushfire prone designation, if you are on the fringe — Roleystone, the hills suburbs, the bushland edges out north. It is a yes/no flag here and a Phase 4 problem.
• Overlooking, drawn as a cone from the neighbour’s upper window, not a dot.

Mark the opportunities, not just the problems

This is the half that gets skipped, and it is why amateur plans read as defensive. Work through the constraint list and ask what each one enables.

• Deep summer shade under a retained marri or jacaranda is the only place anyone will sit in February. That is the outdoor room, already located.
• The area you cannot build over because of the soakwell is a perfectly good lawn or low garden bed.
• A north-facing wall is a winter sun trap and a place for espalier or citrus.
• The one genuinely level area is the cheapest square metres on the site — that is where the large paved space belongs unless there is a reason otherwise.
• A mature tree is fifteen years you cannot purchase.

Reading it like a designer

When the drawing is finished, interrogate it with the three questions a designer asks:

1. Where is the site telling me to put the main outdoor space? Usually the intersection of shelter, level ground, summer shade, winter sun and short travel from the kitchen door. Often there is only one such place, and the drawing hands it to you.
2. What can never move? Services, retained trees, boundaries, and levels against the house. Everything else is negotiable.
3. Where is the money? Which parts of this site cost three times as much per square metre — limestone, steep fall, no machine access — and is the design putting the expensive work there for a good reason?

If you cannot walk someone through the drawing in five minutes, it is either incomplete or over-drawn. Both are fixable in one more pass.

Where this goes next

Phase 4 takes each hard constraint and asks whether it triggers an approval — the R-Codes and your council for setbacks and boundary walls, and bushfire and dieback if the map flagged your lot.

Then Phase 5 puts tracing paper over this exact sheet and starts drawing bubbles. Functional zoning is literally this drawing with activities laid over it — which is why the effort you spend here is the cheapest design work you will ever do.