Why the budget should be aligned from the earliest stages of the project

The available investment shapes the area to be worked on, the materials, the infrastructure, the size of the trees and the phasing. Putting this conversation off until the detailed design can mean reworking a scheme that has already been developed.

Aligning the budget does not mean always choosing the cheapest option. It means understanding where the client wants to concentrate resources and which parts can be simplified, postponed or dropped without losing the logic of the whole.

At this stage Diaplant does not publish universal figures for design or construction. The cost depends on the site, the access, the brief and the level of intervention.

The first step is to tell needs from wishes.

Access, drainage, safety and resolving levels may be essential. A swimming pool, an outdoor kitchen, mature trees or special materials may rank differently for each client.

The briefing sorts these choices before the design assumes that everything will be built.

A list with no hierarchy produces a project with many areas and little clarity.

Price per square metre is not enough to compare gardens.

A small area with high walls, difficult access and a pool can call for more investment than a larger plot with agricultural soil and simple planting.

Earthworks, retaining structures, stone, underground services, water and logistics have a major impact.

The condition of the soil and the need for drainage only become clear after analysis.

The same design can be built with materials and systems of different cost.

A substitution should not be made on appearance alone. Durability, sub-base, joints, maintenance and origin all count.

A local stone can cut transport and reinforce identity, but it needs to be available and properly detailed.

The sample should be approved in context and not just in a photograph.

Size on planting day changes the investment.

Mature trees create immediate scale and call for years of production, transport and a crane. Smaller sizes need time and can be simpler to install.

The design can concentrate mature specimens in structural positions and use young stock in other areas.

Species, form and quantity are adjusted without turning the garden into a collection of small plants just to bring down the initial figure.

Irrigation, drainage, electricity, sub-bases and waterproofing account for a significant part of the investment and stay hidden.

Cutting these components without clear criteria can cause problems after handover.

The client needs to understand that the visual effect depends on this foundation.

The design should separate what can be phased from what has to be in place from the start.

At concept design stage, alternatives can be compared.

One option may keep the layout and change the material, the plant size or the dimensions. Another may remove a function or move it to a later phase.

The scenarios should show differences in result, maintenance and timescale.

It is not enough to present three figures without explaining what changes.

At the start, the work is done with orders of magnitude and assumptions.

As levels, areas and materials are defined, the estimate becomes more detailed.

At detailed design stage, the measured quantities make it possible to invite comparable tenders.

Every estimate should state its date, scope, exclusions and degree of accuracy. Market prices and availability change.

Building in phases can spread the investment, but it needs planning.

Services, drainage and ground modelling for the later phase may have to be prepared at the outset. Otherwise, work will have to be demolished.

Mature trees may need to go in early because of access.

A first phase should work and be maintained, not look like a site left on hold.

The cost does not end at handover.

Trained forms, intensively managed lawns, water and delicate materials call for continuous upkeep.

An option with a lower initial cost may use more water and labour. The design should compare the whole life cycle and not just the build.

The client needs to know about this commitment before approving.

When the brief changes, the impact is updated.

Adding a pool alters levels, services, planning consent and access. Swapping a tree can change the crane and the planting hole.

Decisions that seem isolated should be assessed as part of the whole.

Recording changes avoids discovering the overrun only at the end.

Outdoor works come up against ground, services and water that have not always been fully revealed.

The estimate should acknowledge risk and, where appropriate, allow a margin.

Ground investigations and surveys reduce uncertainty, but they do not remove it.

A proposal that is fixed too tightly before the soil is known can convey a precision that does not exist.

The conversation about investment should be clear and discreet, without pressing the client to settle on a number they do not yet understand.

Modelling scenarios helps to form that reference point.

A design does not lose creativity when it knows its limits. It gains the ability to invest in the decisions that really transform the space.

• What a concept design includes
• How to plan for maintenance during the design
• How to build a brief

1. Diaplant’s method for briefing, estimating and phasing.
2. Principles of cost management and measurement in landscape works.