What a planning budget covers and what belongs in build cost

The planning budget versus build cost split matters because the two pots are funded differently and spent at different times. The planning budget is cash out of your own pocket before you own a consent, with no asset at the end of it if the application fails. The build cost is usually funded by a self-build mortgage drawn in stages against work in place. Putting a survey in the wrong pot means either asking a lender to fund something before the drawdown starts, or finding a five-figure line in the planning budget you had not planned for.

A clean way to think about it: if you would still have to pay for it after a refusal, it is a planning cost.

Items that always sit in the planning budget

These are the lines to have priced before you submit anything.

The application fee itself, set in the fees regulations and subject to periodic uplift and annual indexation, so take the figure from the Planning Portal fee calculator at the time you apply. Pre-application advice, where the authority charges for it on a published fee band. Architectural fees to the end of the planning stage, usually expressed as a percentage of the total service or as a stage fee.

Then the validation documents. On a single new dwelling on a greenfield or garden plot that commonly means a topographical survey, a tree survey, an ecological appraisal with a biodiversity metric, a drainage statement and a contamination screening note. Each is a separate commission. Each has its own lead time.

Legal fees for a section 106 obligation, where one is required, including the authority's own legal costs, which are normally payable by the applicant on a bilateral deed. And the planning consultant's fee where one is engaged.

Items that belong to construction

Building Regulations are a separate regime with separate costs and they are construction costs, not planning costs. The building control application fee, the inspection charges, and the design work needed to satisfy the Approved Documents all sit on the build side.

So do the structural engineer's design and calculations, the party wall surveyor, the site set-up, the utility connections, the highway works under a section 278 agreement, and the warranty or latent defects insurance. None of those are needed to obtain planning permission.

Two commonly misplaced items. Energy calculations: the standard assessment procedure work for Part L is a construction cost, while an Energy Statement required by the local validation list is a planning cost, and they are not the same document even though they use overlapping inputs. And measured survey: a measured survey of an existing building for the design is a construction-side cost, while a topographical survey of the site needed for the application drawings is a planning cost.

Overlaps: surveys used for both purposes

Several surveys serve both stages, and the money is best spent once with both uses specified at the outset.

Brief each one for both purposes in the first instance. A ground investigation scoped only to answer the contamination screening question will usually have to be repeated for foundation design, and a second mobilisation of a drilling rig is most of the cost of the first. The same logic applies to hydraulic inputs, as set out in flood modelling inputs and what they add to a report.

Post-consent conditions and who pays

This is the pot that catches self-builders, because it falls between the two budgets and nobody owns it.

A permission will usually carry conditions requiring details to be submitted and approved before works start or before occupation: materials samples, landscaping, drainage details, a construction method statement, tree protection, an ecology method statement, electric vehicle charging and bin storage. Each submission carries an application fee for approval of details, and the fee is charged per request rather than per condition, which is an argument for bundling several conditions into one submission.

Then there is the work the conditions require. A landscaping condition means buying and planting the scheme. A biodiversity condition means delivering the habitat and maintaining it. A construction method statement means following it, which can mean hand digging within a root protection area or restricted working hours.

Biodiversity net gain deserves its own line. Where the statutory regime applies, the metric has to be completed by a competent person under the Environment Act 2021 regime and the biodiversity gain plan has to be approved by the authority before development begins. A Biodiversity Net Gain Assessment is a report type where a competent person is legally required, and where on-site gain is not achievable the cost of off-site units or statutory credits is a real and sometimes large line. Price it before you buy the plot, not after.

Utilities and highway agreements

Utility connections and diversions are construction costs with planning consequences. A connection quotation is valid for a limited period, reinforcement works can need their own consents, and a diversion of an existing main across the plot can force a layout change that takes you back to the drawing board.

Get indicative quotations at the design stage even though the money is spent later, because the figures sometimes change the scheme. Diversions in particular are a cost people discover far too late, as set out in utility diversions and the cost nobody budgets.

Highway works under a section 278 agreement bring the authority's checking and supervision fees, a bond or other security, and often a road safety audit. Those fees are published in each authority's own schedule of charges and they change, so take the current schedule rather than a figure from a previous project.

Community Infrastructure Levy liability, where the charging authority has adopted a schedule, is a development cost rather than a planning fee. Self-build and residential extension exemptions exist, and they have to be claimed on the prescribed forms and accompanied by a commencement notice before work starts. Missing that step loses the exemption, which is among the most expensive administrative errors available to a self-builder.

Contingency and how much to hold

A flat percentage is the wrong tool here, because the risk is lumpy rather than smooth. Size the planning contingency against the specific unknowns in front of you.

1. Count the validation items you have marked as arguable rather than confirmed. Each one is a potential commission.
2. Identify every season-dependent survey in the pack. A bat emergence survey missed in September costs a year, not a fee.
3. Note whether a section 106 obligation is likely, because the legal cost on both sides is a four-figure line at least.
4. Note whether off-site biodiversity units may be needed, which is the largest single variable on many small greenfield schemes.

Then hold a sum that covers the realistic combination of those, and keep it visibly separate from the construction contingency. Construction contingency gets spent on construction surprises, and if the two pots are merged the planning risk is uncovered.

A simple structure for the budget

Four headings, kept on one page.

Pre-consent professional fees: design to planning stage, planning consultant, pre-application charge. Pre-consent evidence: each survey and assessment as a named line with the commissioning date. Consent and legal: application fee, section 106 legal costs, approval of details fees. Post-consent delivery: landscaping, biodiversity delivery and maintenance, condition compliance works, construction management obligations.

Keep the construction budget entirely separate, with its own contingency, and review the boundary between them at the point of consent rather than at the start. The construction obligations that arrive by condition are the most frequently underestimated of the four, and the detail is set out in construction management plan conditions and their cost.

For the narrative documents in the pack, drafting in-house shifts the cost shape. PlanScope prices a single report at £50, with one free report on the Free tier, and Professional at £150 per month or £600 per year. See PlanScope pricing for the current tiers.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.