Do I Need a Party Wall Surveyor for Underpinning My Property?

If your home has subsidence issues or you’re planning a basement extension, you’ve probably heard the term underpinning. It’s a serious structural job that strengthens your property’s foundations—but it also raises some important legal questions.

The big one?

👉 Do I need a Party Wall Surveyor for underpinning my property?

The short answer? Yes—almost always. Underpinning involves deep excavation and structural work that can affect your neighbour’s property, triggering the Party Wall etc. Act 1996.

In this guide, I’ll break down:

✅ When you do (and don’t) need a Party Wall Surveyor
✅ How to serve notice and avoid disputes
✅ The legal risks of skipping the process
✅ Costs and how to keep them low

When Do You Need a Party Wall Surveyor for Underpinning?

The Party Wall etc. Act 1996 applies to any work that could affect a shared wall or your neighbour’s foundations. Since underpinning involves deep excavation and structural changes, it almost always triggers the Act.

You’ll need to serve a Party Wall Notice and appoint a Party Wall Surveyor if:

🔹 You’re underpinning a shared party wall.
🔹 The excavation goes within 3 metres of your neighbour’s foundations.
🔹 The excavation is deeper than your neighbour’s foundations (even if it’s more than 3m away).
🔹 You’re underpinning the entire property, potentially impacting boundary lines.

💡 Pro Tip: Even if your neighbour’s property is detached, underpinning near their foundations can trigger the Act.

👉 Need help? Check out our Fixed Fee Party Wall Service.

What Is Underpinning and Why Does It Trigger the Party Wall Act?

Underpinning strengthens existing foundations by extending them deeper into stable soil. It’s commonly done when:

✔ There’s subsidence or structural movement.
✔ You’re adding extra floors (e.g., a loft or basement).
✔ The original foundations aren’t strong enough to support changes.

Because underpinning involves deep digging and altering structural supports, it poses a risk to neighbouring properties—hence why the Party Wall Act kicks in.

What’s a Party Wall Notice for Underpinning?

If your underpinning project affects a shared wall or is close to your neighbour’s foundations, you’ll need to serve a Party Wall Notice.

Here’s how it works:

📌 Serve notice at least 1 month before starting underpinning.
📌 Your neighbour has 14 days to respond.
📌 If they don’t reply, send a final notice (giving them another 10 days).
📌 If they object or ignore the notice, you’ll need to appoint a Party Wall Surveyor.

💡 Pro Tip: Underpinning makes neighbours nervous—talk to them before serving notice to smooth things over.

👉 We can help you serve your Party Wall Notice hassle-free.

What Happens If My Neighbour Objects?

If your neighbour objects to the underpinning work, here’s what happens:

1️⃣ Both parties appoint Party Wall Surveyors.
2️⃣ The surveyors draft a Party Wall Award—outlining how the work will be done safely.
3️⃣ If surveyors can’t agree, a Third Surveyor is brought in to make the final decision.
4️⃣ Once the Party Wall Award is agreed upon, you can legally begin underpinning.

💡 Want to save money? Get your neighbour to agree to use one Agreed Surveyor for both parties.

👉 See our Fixed Fee Party Wall options here.

What’s in a Party Wall Award for Underpinning?

A Party Wall Award protects both you and your neighbour and includes:

✔ Detailed plans – Showing the underpinning method and depth.
✔ Precautionary measures – Steps to avoid ground movement or damage to neighbouring properties.
✔ Schedule of Condition – A “before” report documenting the state of your neighbour’s property.
✔ Timelines & working hours – To minimize disruption.

💡 Tip: A solid Party Wall Award can save you thousands if disputes arise later.

What Happens If You Skip the Party Wall Process?

Underpinning without following the Party Wall Act is a massive legal risk. Here’s what could happen:

🚨 Neighbour could file for an injunction – Halting your work immediately.
💰 You’d be liable for any damage – Even minor cracks or subsidence on their property.
⏰ Project delays & legal costs – Disputes can drag on for months and cost tens of thousands.

💡 Tip: Always follow the Party Wall process—especially with high-risk projects like underpinning.

👉 Need help? We’ll handle the Party Wall process for you.

Do I Need Building Control Approval for Underpinning?

Yes—underpinning is major structural work, so Building Control approval is essential.

You’ll need to:

✅ Submit detailed plans from a structural engineer.
✅ Have inspections during and after underpinning.
✅ Get a completion certificate once the work passes inspection.

💡 Pro Tip: Building Control ensures your home is structurally sound, while the Party Wall Surveyor focuses on protecting neighbouring properties.

How Much Does a Party Wall Agreement for Underpinning Cost?

💡 Want to save money? Use an Agreed Surveyor and opt for a fixed-fee service.

👉 Check out our fixed-fee pricing here.

How to Keep Party Wall Costs Down for Underpinning

✅ Talk to your neighbour early – Avoid disputes before they happen.
✅ Use an Agreed Surveyor – One surveyor for both parties halves the cost.
✅ Choose a fixed-fee service – No surprises or hidden costs.

👉 See our fixed-fee Party Wall services here.

Final Thoughts

Underpinning is serious work—whether you’re fixing subsidence or prepping for a basement, it comes with risks. The Party Wall Act ensures both you and your neighbours are protected.

✔ Serve a Party Wall Notice before starting.
✔ Get a proper Party Wall Agreement in place.
✔ Use a trusted Party Wall Surveyor to avoid costly mistakes.

🚀 Ready to get started?

👉 Contact Fixed Price Party Wall today—we’ll handle your Party Wall Agreement quickly and at a fixed price!