A standalone arboricultural impact assessment (AIA) typically costs from around £200 as an add-on to an existing tree survey, while a combined survey-plus-AIA package for a development site usually runs £500–£1,000 — with larger, more complex sites costing £1,500 or more. But the headline number is only half the story: what your council actually demands at validation is what determines your real bill.
An arboricultural impact assessment is rarely bought in isolation, so its price only makes sense in the context of the wider BS5837 document stack. This guide breaks down what you pay for, why the AIA element moves the way it does, and how local rules quietly change the total.
Where the AIA sits in the pricing
An AIA is not a survey. The BS5837 tree survey is the systematic record of every relevant tree — species, height, stem diameter, crown spread, condition, its BS5837 retention category (A, B, C or U) and its calculated root protection area. The AIA is the next document: it assesses your proposed layout against that survey data, identifying which trees must be removed, which are retained, and where the design conflicts with trees (excavations, level changes, incursions into root protection areas, and shading pressure for future occupiers).
Because the survey usually comes first, consultants tend to quote the AIA either as an add-on or as part of a bundle:
| What you buy | Typical price | Notes |
|---|---|---|
| AIA as a standalone add-on | from ~£200 | Assumes a usable survey already exists |
| Tree survey + AIA (typical development) | ~£500–£1,000 | The common combined purchase |
| Full BS5837 planning package (survey + TCP + AIA + TPP + preliminary AMS) | ~£400–£1,500+ | Everything needed for validation |
| Large / complex sites, many trees, phased schemes | £1,500 – several thousand | Scales with tree count and conflict |
These are indicative UK market ranges from arboricultural providers, drawn from 2024–2025 pricing. They are promotional in origin and vary considerably by site, so treat them as bands rather than fixed figures.
What drives the AIA element up
The survey cost is largely a function of how many trees are on and around the site. The AIA element is driven by something different: how much your design fights the trees.
- Number of retained trees affected. Each tree whose root protection area your layout encroaches on needs assessment and, usually, a mitigation route. More conflicts means more analysis and more chargeable time.
- Severity of the conflict. A layout that keeps roads, foundations and services clear of root protection areas is quick to assess. One that drives them through the RPAs forces the consultant to work through no-dig construction, engineered foundations and redesign options — the expensive part.
- Off-site and neighbouring trees. Trees on adjacent land whose canopies overhang, or whose RPAs project into your site, must be assessed too. A boundary lined with third-party trees adds work, because the RPA of an unremarkable-looking neighbour's tree can still land a no-build constraint squarely on your proposed footprint.
- Protected-tree status. Where trees carry a Tree Preservation Order or sit in a conservation area, the assessment carries more weight and scrutiny, and the report has to justify itself against a criminal-law-backed regime that is separate from the planning application.
- Design maturity. An AIA written against a fixed, tree-hostile layout often triggers a redesign loop. Involving the arboriculturist before the layout is set keeps the AIA — and the total bill — lower.
A worked example: the rear extension near a neighbour's oak
Consider a single-storey rear extension where a neighbour's mature oak — stem diameter 600mm — stands 1.5m the other side of the fence. Its root protection area is a circle of radius 12 × 0.6m = 7.2m, capped well below the 707m² ceiling that only applies to very large stems. That 7.2m circle reaches roughly 5.7m into your garden — straight across where the extension foundations and a new patio would go.
Here the AIA earns its fee. It cannot simply say "the oak is retained"; it has to show how the foundations, drainage and hard surfacing can be built without excavating, compacting or raising levels inside that RPA. That usually means specifying a no-dig or engineered foundation solution and cellular-confinement surfacing for the patio, all of which the consultant has to design and defend. A layout that pretended the oak wasn't there would be quick to write and quickly rejected. This is why two projects with an identical tree count can carry very different AIA fees.
Why your council changes the bill
This is the point most cost guides skip: the requirement is set locally. BS5837:2012 is a British Standard containing recommendations, not law. The compulsion to produce — and pay for — an AIA comes from three separate places, and how they apply depends on where you are:
- Your local planning authority's validation list, which decides whether you must submit a full AIA (plus a tree protection plan and preliminary method statement) at the point of application, or whether a survey alone will get you validated.
- Planning conditions, where permission is granted subject to a detailed method statement and protection plan being approved before works start.
- Statutory protection — TPOs, conservation areas and, near ancient woodland or veteran trees, national policy — which independently raises the bar.
Validation checklists and tree-officer expectations genuinely vary by authority. Some councils demand the full package up front; others accept a survey and impact assessment and condition the rest. Areas with dense TPO coverage, extensive conservation areas, or nearby ancient woodland or veteran trees attract more scrutiny and therefore a more thorough — and more expensive — assessment. You can compare how requirements differ in Leeds, Manchester and Lambeth, each of which sets its own validation detail. Before you budget, check your authority's validation requirements and confirm whether any of your trees are protected.
PlanWatch tracks live tree-related planning activity council by council, so you can see how tree issues are actually being handled in your area and check whether the trees on or near your site already feature in local applications. Look up your own council to gauge the local climate before you instruct.
Note too that this is an England-centric picture. Wales, Scotland and Northern Ireland run parallel but distinct statutory regimes, so if your site is in a devolved nation the documentation triggers — and the fee drivers — differ.
The false economy trap
The single biggest cost mistake is treating the AIA as a box-ticking formality and buying the thinnest one available. A weak AIA that the tree officer rejects — or one that ignores neighbouring trees, or grades trees optimistically to make a scheme look deliverable — gets your application invalidated or refused. You then pay again for revisions, a redesign, and the delay itself, which on a development can dwarf the report fee. See cheap tree surveys: the hidden costs for how this plays out.
How to get an accurate quote
Give the consultant enough to price properly: the site address, a rough tree count (and whether any are on neighbouring land or protected), your draft layout if you have one, and which council you are dealing with. For the wider picture, see our full breakdown of tree survey cost and what affects the price of a tree survey. When you are ready to instruct, our guide to finding a tree surveyor explains which accreditations — an Arboricultural Association Registered Consultant or an ICF Chartered Arboriculturist — carry the most weight with planning officers. To see how the AIA reads once written, our arboricultural report example walks through a typical document section by section.
The AIA is the document that proves your scheme can actually be built without damaging the trees the council wants kept. Spending a little more to get it right first time is almost always cheaper than the alternative.