Trees shape Cornish streets, gardens and landscapes, but they also shape what you can build. A Tree Preservation Order (TPO), conservation area rules, root protection areas and the way roots interact with foundations can all affect extensions, new builds and groundworks. Ignoring them risks refusal, enforcement or later structural problems. This guide explains the planning and groundworks angle in plain terms. It is general guidance — always check with Cornwall Council and your designer for your own trees and proposals.
Tree Preservation Orders (TPOs)
A TPO is a legal order that protects specific trees, groups or woodlands. If a tree is covered, you generally need the council’s consent before you cut it down, top it, lop it or carry out work that could damage it. Unauthorised works can lead to significant penalties. TPOs can apply to trees on your land or on neighbouring land that still affect your project.
Before you design an extension or outbuilding, ask Cornwall Council whether any TPOs affect the site, and walk the plot with an arboriculturist if large trees sit close to the proposed works. Do not assume a tree is unprotected because it is in a private garden.
Trees in conservation areas
Even without a TPO, trees in a conservation area often have statutory protection. As a general rule in England, you must notify the local planning authority before carrying out certain works to trees above a size threshold in a conservation area, unless an exception applies. The council then has a period to decide whether to place a TPO or allow the works.
If your project sits in a conservation area or National Landscape (AONB) setting, tree issues often sit alongside design and heritage concerns. Our guide to building in AONBs and conservation areas covers the wider planning context, and planning permission in Cornwall outlines how applications are typically approached.
Root protection areas and layout
Roots need space and an undisturbed soil structure. British Standard guidance on trees in relation to design and construction uses a root protection area (RPA) — broadly a calculated zone around the stem where digging, compaction and level changes should be avoided or carefully controlled. As a rule of thumb, the bigger the stem diameter, the larger the RPA, though shape can be adjusted by an arboriculturist where roots are constrained by roads or walls.
Good project planning usually means:
Surveying tree positions, stem diameters and canopy spreads early
Setting foundations, drains and driveways outside RPAs where possible
Using specialist foundation designs or no-dig surfaces where conflict is unavoidable
Protecting RPAs with fencing during the build so plant and materials do not compact the soil
Moving a footprint by a metre or two at sketch stage is far cheaper than redesigning foundations after an objection.
Foundations near trees
Trees take moisture from the soil. On shrinkable clays this can affect foundation heave and settlement; even on Cornish soils with rock, fill or local clay pockets, large trees near shallow foundations deserve respect. Building near trees may mean deeper foundations, pile or raft solutions, or Foundation Depth tables linked to species and distance — your structural engineer and Building Control will expect this to be considered.
Conversely, removing a mature tree that has long dried a clay soil can sometimes create heave risk for existing foundations. Tree removal for development is therefore both a planning/ecology issue and a structural one. Coordinate arboricultural advice with groundworks and foundations; our groundworks guide explains site investigation more widely.
Cornwall Council consents and the planning application
For works to protected trees you will usually need to apply to Cornwall Council (or follow the conservation area notification process). For a building project, tree information often forms part of the planning submission: a tree survey, arboricultural impact assessment and method statement showing how retained trees will be protected during construction.
Expect planners to look at:
Whether retained trees remain viable after the build
Impacts on public amenity and landscape character
Replacement planting if removal is justified
Construction access, scaffolding and storage clear of RPAs
New homes, barn conversions and home extensions on tree-rich plots should treat arboriculture as an early design input, not a late problem to “deal with on site”.
Building near trees FAQs
Can I remove a tree in my garden for an extension?
Only if it is not protected by a TPO or conservation area controls (or other legal constraints), and even then planning may require justification and replacements. Check with Cornwall Council before any cutting.
What is a root protection area?
It is the zone around a tree where roots should be protected from digging and compaction, calculated from stem size using standard guidance and refined by an arboriculturist.
Do tree issues affect Building Regulations?
Planning and tree consents are separate from Building Regulations, but foundation design near trees is a structural/Building Control matter as well as a planning one.
What if my neighbour’s TPO tree overhangs my land?
Ownership and TPO rules both matter. You may have common-law rights regarding overhanging branches, but TPO consent can still be required for cutting. Take advice before acting.
Talk to us about your project
If trees sit close to a planned extension, new build or groundworks package, we can help you think through buildable foundation and protection options alongside your designer and arboriculturist. Call Cornish Building Company on 01208 816991 or contact us to discuss your site.
