Landscaping & Irrigation

Landscaping covers the planted and hard-landscaped external areas of a site: trees, garden beds, lawns, planters, podium and roof gardens, green walls, landscape walls and features, and the irrigation systems that water them. Landscaping interacts with the building more than its cost suggests: trees damage foundations, drains and pavements; planters on podiums and roofs load the structure and test waterproofing; irrigation leaks soak walls and membranes; and in bushfire areas vegetation sets fire risk.

Landscape works also carry statutory and planning obligations: tree preservation controls, landscape conditions on development approvals, and bushfire vegetation management, all of which constrain what an owner can change.

What shortens life:

• Poor plant selection for the site: large trees near buildings, vigorous roots near drains.
• Lack of maintenance: unpruned trees, untended irrigation.
• Drainage failures in planters.
• Construction damage to tree roots.

Trees outlast most building elements but change constantly: a sapling planted near a wall becomes a large tree within the life of the building, and its effect grows with it.

Tree and limb failure

Trees with decay, cracks, weak forks, root damage or dieback drop limbs or fall in storms. Trees damaged by construction often decline years later. Failures over car parks, footpaths and play areas cause injuries and damage.

Root damage to buildings and services

Roots draw moisture from clay soils, causing foundation subsidence; they enter and block drains through joints; they lift pavements and walls. Removing trees on clay can cause heave.

Podium and roof planter leaks

Planters over occupied space depend on waterproofing, root barriers and drainage. Roots penetrate unprotected membranes, drains block with soil and roots, and leaks appear in car parks and apartments below. Saturated planters can also exceed the structure's design load.

Irrigation faults

Irrigation leaks and overspray wet walls, footings and windows, causing damp, efflorescence and decay; systems run in rain; connections to drinking water lack backflow protection.

Bridging damp-proof courses and termite barriers

Garden beds and mulch heaped against walls cover vents, bridge damp-proof courses and give termites hidden access over barriers.

Vegetation and bushfire

In bushfire-prone areas, vegetation and mulch close to buildings carry fire to the walls, decks and roof gutters.

Construction damage

Trenching, excavation, compaction and level changes within a tree's root zone kill roots and destabilise trees, often with decline appearing years later when the link is forgotten.

On site

• Trees with dead limbs, cracks, cavities, fungal fruiting bodies, lean or root lifting.
• Large trees close to buildings on clay soils.
• Leaks and staining under podium planters; plants growing from drainage outlets.
• Irrigation spraying onto walls, windows and paving; wet patches and leaks.
• Garden beds above damp-proof courses and vents; mulch against walls.
• Green walls with dead plants, leaks and staining below.

In the records

• Arborist reports and tree management records.
• Landscape maintenance contracts.
• Irrigation drawings and backflow tests.
• Leak history under planters.

• Soil levels raised around tree trunks, or trenches cut close to trees, signs of root damage.

Root problems are distinguished from other causes by position and timing: damage that follows the line of a tree's roots, worsens in dry seasons and is worst nearest the tree points to the tree; damage unrelated to tree positions points elsewhere.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

Tree findings are graded by consequence as well as defect: the same decay in a tree over a car park, a footpath or a play area is a higher grade than in a tree in an unused corner of the site.

A qualified arborist for trees; a landscape architect or contractor for landscaping; a waterproofing specialist for planters.

• Tree risk assessment using a recognised method, prioritising trees near people and buildings.
• Root and foundation review where trees are near buildings on clay.
• Planter investigation: drainage, root barriers, membrane condition, saturated weight against design loads.
• Irrigation audit: leaks, overspray, controllers, backflow devices.
• Building interface check: beds, mulch and paving against walls, vents and barriers.
• Bushfire assessment where relevant.

The report should give tree risks, building interactions, planter and irrigation issues, and a maintenance and renewal plan.

Tree risk is judged by the likelihood of failure and the consequence: a defective tree over an empty field is less urgent than a sound-looking tree with a structural defect over a children's play area or a busy entrance.

• Tree work: pruning, removal, cabling or replacement with suitable species, with heave assessed before removing trees near buildings.
• Root barriers between trees and buildings or drains.
• Planter rectification: new membranes with root barriers, drainage cells and clear outlets.
• Irrigation repair: redirect sprays, fix leaks, rain sensors, smart controllers, backflow devices.
• Clearances: lower beds and remove mulch from walls, vents and barriers.
• Vegetation management in bushfire areas.
• Green wall renewal.

• Tree protection during any works near trees, with fencing and root protection zones.
• Water-efficient landscaping: drought-tolerant planting and drip irrigation, reducing water use and leaks.
• Maintenance programme setting pruning, irrigation checks, planter drainage clearing and mulch control.

Landscape maintenance is a recurring contract. Arborist assessments recur. Tree work is per tree. Planter rectification is a lump sum with soil removal and reinstatement. Irrigation upgrades are lump sums.

Safety tree work is immediate; planter rectification is lifecycle or failure; maintenance is repairs and maintenance.

Tree removal near buildings on clay can require phased work and monitoring to manage heave. Podium planter rectification usually means removing soil and plants by hand or crane, which often costs more than the waterproofing itself.

• Australia. AS 4970 covers protection of trees on development sites and AS 4373 pruning; tree preservation controls apply in many council areas; AS 3959 sets construction in bushfire-prone areas.
• United Kingdom. BS 5837 covers trees in relation to construction; tree preservation orders and conservation areas restrict work on trees; occupiers owe a duty of care for tree safety.
• United States. ANSI A300 sets tree care standards; local tree ordinances apply; wildland-urban interface codes set vegetation clearances in fire-prone areas.

In all three jurisdictions, landscape conditions attached to planning approvals can require planting to be kept or replaced, and trees on boundaries create shared liability with neighbours. Strata and condominium landscaping is common property, with by-laws on what owners may plant on balconies and in private courtyards over shared structures.

• Arborist reports and tree management records.
• Tree preservation orders or controls.
• Landscape maintenance contracts.
• Irrigation drawings and backflow test certificates.
• Planter waterproofing records and leak history.
• Bushfire assessments.

• Planning approval landscape conditions.
• Records of works near trees.
• Strata by-laws on planting.

• Bushfire attack level assessments where relevant.