Trees are great. But building near them can be uniquely challenging. Whether you’re working in a Root Protection Area (RPA), somewhere that has a Tree Preservation Order (TPO) in place, or simply on a project for a client who values all that trees can bring to a site, there are multiple problems to be overcome. Not least of which is finding the right foundation solution. One of the most effective and widely approved methods for building within RPAs is the use of helical piles.
Constructing Foundations Without Harming Tree Roots
What is a Root Protection Area?
A Root Protection Area is a designated zone around a tree intended to protect its root system from damage during construction. RPAs are defined in arboricultural standards and local planning regulations, typically calculated based on the tree’s trunk diameter. The RPA is intended to define the minimum area required to maintain tree health and stability, and to limit activities that may impact this. Such as excavation, soil compaction, trenching, or changes in ground level.
What is a Tree Preservation Order?
A Tree Preservation Order is very similar in nature to an RPA, in that it’s a legally binding order intended to protect specific trees or groups of trees. The primary difference is that it also covers the areas above the soil, which means that the relevant trees cannot be cut down, pruned, damaged, or destroyed without prior consent from the local planning authority. Any construction work near a tree protected by a TPO, including groundworks that may impact its roots, must comply with strict regulations. Unauthorised work can result in substantial fines or legal action.
Regulations and planning constraints
Most local authorities require an Arboricultural Impact Assessment (AIA) or Tree Protection Plan (TPP) for any proposed project near protected trees. These documents outline what construction methods are permitted. More often than not, they prohibit traditional foundation types, such as strip footings or pad foundations, due to the extensive excavation they require.
If you don’t comply with RPA regulations, planning permission is likely to be denied. In which case, you’ll face expensive redesigns. So, it makes more sense to seek foundation solutions that meet both structural and arboricultural requirements.
Why traditional foundations are a problem
A lot of ground disturbance is involved in the laying of conventional foundations. This includes deep excavation, removal of soil, and heavy machinery access. Within an RPA, this can sever major roots, compact soil, and disrupt natural drainage, all of which are harmful to trees.
Even small amounts of excavation can have a substantial impact on tree health, particularly for mature specimens. And this can have significant ramifications if that tree happens to be protected. This is why alternative, low-impact foundation systems are often required.
Why helical piles are the approved solution for RPAs
Helical piles, also known as screw piles, have become the preferred foundation solution for construction within Root Protection Areas. And there’s a good reason for this. Unlike traditional foundations, screw piles are installed by rotating them into the ground, rather than excavating soil. This process displaces minimal soil and allows piles to be positioned precisely to avoid major roots. Installation can often be carried out using compact, low-impact machinery – or even by hand, where there is a need – further reducing disturbance within sensitive areas.
Key benefits of using screw piles within RPAs
- Minimal excavation and soil disturbance
- Reduced risk of root damage
- Immediate load-bearing capacity
- Installation in confined or restricted access sites
- Compatibility with suspended floors and elevated structures
Because screw piles can support structures above ground level, they allow airflow, water movement, and continued root growth beneath the building. This is an important factor often required by arboricultural consultants.
Building with confidence in RPAs
At UK Helix, we specialise in designing, supplying, and installing foundation solutions for challenging sites, including projects within Root Protection Areas. Our experience working alongside arborists, engineers, and planning authorities ensures that our screw pile designs meet both structural demands and tree protection requirements.
By carefully assessing ground conditions, pile layout, and loading requirements, we help clients achieve planning approval while preserving trees. Whether for extensions, decks, walkways, or new structures, helical piles offer a proven, regulation-compliant approach to building near trees.
Constructing within an RPA or where a TPO is in place doesn’t have to mean compromising project viability. With the right knowledge and foundation system, development and tree preservation can go hand in hand. Helical piles provide a modern, low-impact solution that aligns with arboricultural regulations and sustainable construction principles, making them the foundation of choice for RPA projects.
Do you need support finding the right foundation solution for a project in an RPA? Get in touch with UK Helix.