Building on peatland

Question

I want to build a wooden/composite garage/shed 20' x 14' in my garden but having dug a trial hole the soil is mainly peat and goes down around 7' to 8' in depth. This peat was removed and replaced with stone when the house was built but this not a practical or cost-effective route to take for the garage. Is a screw pile the best way to go?

Steve · Accepted Answer

Hi , I would suggest that this is a  decent option , still can work out fairly costly if not surveyed correctly, I would make certain to incorporate the screws within structural floor base and blend into rebar construction to floor, clean surrounding floor area and remove any loose material , this will provide a great wide tight compact shoe footing for build, 
Good luck
Best wishes
Steve

Jack · Answer

I would say piling is the best way to go with this

Luke · Answer

I would use shuttering and re bar to make a concrete Base roughly 100-300mm

Imad · Answer

Given that your soil is primarily peat and can be quite soft and compressible, traditional foundations like concrete may not be ideal, as they could settle over time due to the weak soil. Using a screw pile foundation is indeed a good solution in this situation. Here's why:

Why Screw Piles are a Good Choice:
Stability in Weak Soils: Screw piles (also known as helical piles) are designed to penetrate deep into the ground and anchor into more stable soil or rock beneath the peat. This makes them ideal for areas with soft, compressible, or unstable soils like peat.

Minimally Invasive: Unlike traditional excavation methods, screw piles do not require large-scale soil removal or deep digging, which can be costly and disruptive. The piles are simply screwed into the ground, making it a more efficient and less invasive process.

Load-Bearing Capacity: Screw piles are capable of supporting significant weight, which makes them suitable for structures like your 20' x 14' garage/shed, especially considering they can anchor into the more stable layers of soil beneath the peat.

Quick Installation: The installation process is relatively quick, as screw piles can be installed in a day or two, depending on the size of the project. This can save you time compared to digging out and replacing the peat or installing a full concrete foundation.

Long-Term Durability: Since screw piles are typically made of galvanized steel, they are resistant to corrosion and will hold up well over time, especially in conditions like peat soil, which can be quite acidic.

Lukasz · Answer

Foundation Options

1. Ground Screws / Helical Piles (best solution in the UK)

Mechanically screwed into stable strata below the peat.

Provide immediate load-bearing capacity, no need for concrete.

Quick installation, minimal excavation.

Perfect for light timber/composite buildings, sheds, garages, garden rooms.
👉 This is usually the most cost-effective and practical solution for peat soils in the UK.

2. Floating Slab / Raft Foundation

A reinforced concrete slab over compacted hardcore.

On peat, risk of differential settlement is high → not recommended for larger structures (better for small sheds only).

3. Driven or Bored Concrete/Steel Piles

Technically effective but expensive, more suited to houses or heavy structures.

Sajawal · Answer

Hi, thanks for your question. Based on your soil conditions (deep peat layer), using screw piles is actually a very good option. They’re ideal for soft or unstable ground where traditional concrete foundations would be costly or difficult. Screw piles can reach deeper, more stable layers below the peat and provide a solid base for your wooden or composite garage.

They’re also quicker to install, cause less ground disturbance, and are more cost-effective than full excavation and backfill. I’d be happy to take a closer look at your site and help plan the right solution for your build. Let me know if you’d like to discuss it further.

Karl · Answer

You need to dig to good ground building regulation for example is 750mil not saying you have to go to that depth just to good ground for what you need

Adrian · Answer

Yes, screw piles are generally the best option for building on deep peat, as they transfer the load to stable soil below, avoid large-scale excavation, reduce settlement risk, and provide a solid base for your garage.

Building on peatland

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