Cost of underpinning bay windows

Bay windows can be one of the most charming features of a property, but sadly they’re also at risk of the dreaded subsidence. Subsidence can be one of the most costly problems you can deal with as a property owner, so we’ve put together this guide on the cost of underpinning bay windows.

If you’re experiencing problems with subsidence and it’s affecting your bay windows, it’s time to seek professional help to get things sorted. Repairing bay windows isn’t something you can do as a DIY job, underpinning will require expert help and the involvement of a structural engineer to inspect and assess the work needed.

All prices included in this article are meant to serve as a guide but for accurate costs, we recommend you speak to your local construction expert and ask for a detailed breakdown of prices for the work.

How much does underpinning a bay window cost?

The average cost of underpinning a property is around £12,500. If you’re looking at the cost of underpinning bay windows per metre then it’s about £1,500 per metre.

Before starting any underpinning work for your bay windows, you’ll need to hire a structural engineer to assess the extent of the problem and advise on the best way to move forward. The average cost of a structural engineer is about £70 per hour.

Underpinning isn’t the only option for dealing with subsidence, and it does tend to be one of the more expensive options. To find out more about the types of underpinning and the costs of repairing damage caused by subsidence, check out our guide to subsidence repair costs.

Factors affecting the cost of underpinning a bay window

As with all house repairs or improvements, the price you pay will vary depending on your individual circumstances. The main factors that will affect the cost of underpinning bay windows include:

• Size of the property
• Extent of the subsidence
• Underpinning method
• Quality and quantity of materials used
• Any party wall agreements needed
• The time it takes to complete the work
• Where you live

What does underpinning mean?

It’s important to understand what underpinning is. Basically, it’s a method used to rectify properties that have suffered structural damage due to subsidence. Underpinning involves excavating the problematic soil underneath the property and replacing it with stronger materials to strengthen the foundations by giving it deeper footings.

The newly constructed base for the foundations will stabilise the property and hopefully cease any further damage. It’s worth noting that underpinning a property can affect insurance policies so, if you’re buying a property, it’s always worth checking if any underpinning has been done.

What are the common signs of subsidence?

If you’re worried about subsidence, there are a number of tell-tale signs that you can look out for, including:

• Cracks in walls, floors, ceilings or joints.
• Sloping floors, walls or ceilings.
• The property leans to one side.
• Doors or windows are stuck and don’t close properly.
• Gaps in between bricks, doors and window frames.

If in doubt, we recommend you have your property inspected by a qualified structural engineer or chartered surveyor. They will be able to tell you whether your property needs underpinning.

What causes bay window subsidence?

Subsidence is the weakening of the support under the house, typically caused when the ground under the foundations of a property starts to sink, taking the foundations with it. One of the most common causes is a low level of moisture in the ground, so it then starts to shrink.

Subsidence is often most notable after a long period of very dry weather. Not commonly a problem in the UK, but with increasingly hot summers subsidence is a real problem.

Useful bay window underpinning checklist

• As soon as you notice any signs of subsidence, contact a structural engineer or chartered surveyor to inspect your property.
• Once you’ve decided you need to underpin your property, speak to your local construction experts for their professional advice on the most appropriate underpinning method to use.
• If you share a party wall you’ll need to apply for a party wall agreement before commencing any underpinning work.
• Shop around for fair and competitive costs for underpinning bay windows.
• Always hire tradespeople with relevant experience and ask to see examples of their previous work.
• When hiring a tradesperson, check the ratings and reviews from recent customers to confirm the quality of their work.