Pile Foundations in Surrey | How Deep Does Bored and Mini Piling Need to Be?

As a team of experienced piling contractors, we frequently encounter the question of "How deep does bored piling and mini piling need to be?". The answer, unfortunately, is not so straightforward. The depth of pile foundations depends on various factors, including the type of foundation that we use. Pile foundations, also classed as deep foundations, were initially reserved for large-scale construction in Surrey. With the development of smaller piles, like mini piling, we now use this foundation system for domestic buildings as well.

Horner Foundations can also use raft foundations and RC ground beams on domestic projects. If you need us for related services, such as underpinning or for basement construction, we can help. We are well-known in Surrey for our professionalism, and for the pride and passion we bring to every job.

The purpose of bored piling and mini piling is to provide essential support for structures by transferring their weight load to underlying layers of soil or rock strata with adequate bearing capacities. Naturally, the heavier the above-ground load, then the deeper that the foundations need to run.

Several other factors also influence the depth of pile foundations, including:

Ground Conditions

Soil type plays a significant role in determining the depth or type of mini piling required. Different soil types include rock, gravel, sand, clay, peat and chalk. Soil types like sand, peat and clay, which are less stable, will often necessitate deeper pile foundations. To accurately identify the soil type on a project in the Surrey area, structural engineers complete a full, detailed assessment.

Proximity to Other Structures

The proximity of a building to existing structures can also impact the depth and type of bored piling needed. It is crucial to assess potential interactions with nearby buildings and to determine the most suitable solution. There are other factors we need to consider too, such as whether or not the eventual workspace will be enclosed, have limited headroom or be hard to access.

Types of Piles Used

Different structures demand different pile foundations. Whether it's bored piling, driven piling, mini piling or geothermal piling, selecting the right type is essential for optimal structural support. At Horner Foundations, our structural engineers play an integral role in the design and specification of the project and make strategic calculations based on soil types and load capacities.

Types of Pile Foundations

For the uninitiated, pile foundations (and raft foundations) will be challenging concepts but for our piling contractors, they are critical components in all forms of construction. Here, we look at a variety of different pile types so that our clients in Surrey might better understand what we can do for them.

Driven Piles

Ideal for supporting buildings, towers, walls and bridges, driven piling comes in various materials and lengths. Some examples include:

• Steel H Section Piles (up to 36m in length) – Often used if a job needs deep foundations and is also suitable for marine structures
• Screw Piles (up to 24m in length) – Unique screwing method minimises soil displacement. Ideal for sheds and garden outbuildings
• Tube Piles – Used for heavy load support. Suitable for buildings and for bridges, and essential for some forms of wall construction
• Concrete Piles (up to 30m in length) – Versatile and suitable for most ground types. This is one of the most common methods of piling
• Timber Piles (up to 12m in length) – Suitable for smaller properties with limited access but widely used to make jetties and sea defences

Bored Piling

Also known as replacement piles, bored piles involve the removal of soil and filling the hole with poured concrete in situ. These piles can reach lengths of around 40 meters and are commonly used for taller buildings with significant vertical loads. Smaller builds benefit from raft foundations and RC ground beams, but bored piling is exceptional for projects with heavier loads.

Mini Piling

With diameters which range between 100mm and 600mm, and capable of reaching depths exceeding 50m, mini piling is versatile and applicable in a variety of soil types. Mini piles are commonly used for underpinning and in retrofit basement construction to strengthen the existing structures, especially in areas with restricted access or in confined spaces with minimal headroom.

Geothermal Piling

These piles serve a dual purpose, providing support to buildings and acting as a heat source for geothermal energy. Depths of geothermal piles will depend on the ground conditions. Geothermal piles are sustainable, and they act as an environmentally friendly energy source by utilising the low-grade heat in shallow ground conditions. They help to heat or cool supported structures.

Piling for Extensions

For house extensions, deep piling is rarely necessary. Strip foundations, raft foundations, RC ground beams or trench-fill foundations will generally suffice. However, in cases where the soil is unstable, then pile foundations may still be required. A good indicator is to have our piling contractors examine your existing foundations. Often, extending the current foundations will suffice.

Choosing the Right Foundations

Determining the type and depth of piling required without visiting the site is challenging. As seasoned specialists in pile and raft foundations, we offer our unparalleled advice and expertise for projects throughout the Surrey area. To explore your options, or to schedule a visit with our piling contractors, please contact us. Horner Foundations will assess ground conditions and provide the most suitable and cost-effective solutions for your construction needs.

With underpinning and basement construction services available too, we are a dependable choice for bringing the groundworks phases of construction projects to a safe, timely conclusion with the minimum of upheaval.