If you suspect your home has signs of subsidence, don’t ignore them!
It is much cheaper and much easier to fix subsidence that has been caught early, than a problem that has been ignored for months.
So, how exactly do you fix subsidence?
Subsidence treatments include tree maintenance or removal, repairing leaking pipes and resin injections. The most expensive, invasive treatment is underpinning. Thankfully, less than 10% of properties suffering from subsidence need underpinning. The treatment required will depend on the cause and severity of the subsidence.
In this article, we look at the four most common subsidence treatments in greater detail and set out the steps you’ll need to take in order to fix your subsidence issue.
Just remember to always seek out expert advice and listen to the professionals before you grab your toolkit and make any drastic decisions!
How do you fix subsidence?
There are a number of different treatment methods out there to fix subsidence. The treatment method that’ll be right for you will depend on the cause and the severity of the subsidence.
The four most common ways to fix subsidence are:
- Tree maintenance or removal
- Repairing leaking or burst pipes
- Resin injections
Let’s take a look at each treatment option in greater detail below…
1. Tree management/maintenance
Trees can cause subsidence by absorbing significant volumes of water from the soil beneath your property through their root system.
Properties built near trees on clay soil can be particularly prone to subsidence as the soil will shrink in volume, leaving parts of the property’s foundations unsupported.
There are a few different options when it comes to treating subsidence caused by trees…
Felling the tree
If a specific tree has been found to be the main cause of subsidence, having it felled may be a suitable and permanent option to remove the risk of further damage in certain cases.
However, you should always consult with a tree surgeon before doing anything drastic. Sometimes removing a tree can do more harm than good to your home.
When a large tree is removed from an area, the soil below it can become saturated over time, as the water is no longer being absorbed by the tree’s root system. If you live in an area with clay soil, the ground can expand and cause the foundations of the house to rise in places (aka “heave”).
Root barriers aren’t always a guaranteed solution either. A root barrier is an underground wall installed to prevent tree roots causing damage to foundations and water systems.
In practise, it isn’t usually feasible to install tree root barriers to a sufficient depth. Tree roots will often just grow under the barrier, with some roots reaching as deep as 5m or more!
Reducing the tree’s size
An alternative solution recommended by the Royal Horticultural Society would be to manage the problem by reducing the tree’s size. This is done by pruning the crown volume. RHS states that to be effective, “pruning needs to reduce the crown volume of the tree by at least 70% and be repeated on a regular basis such as every three years”.
A tree surgeon will be able to recommend the best course of action for your particular case.
2. Repairing leaking or burst pipes
Water leaks can wash away fine particles in the soil underneath the foundations of your home. If the problem isn’t fixed, subsidence can occur when the property’s foundation is no longer supported by the ground beneath it.
In order to fix subsidence caused by water leaks, you’ll need to firstly find out which pipe is to blame.
To do this, you can get a CCTV drain survey. A CCTV drain survey is carried out using remote-controlled camera units which can determine where the leak is located.
Once you’ve established the location of the leak, the drain can then be repaired or completely replaced if necessary.
Only once the leaking drain has been fixed should you begin to think about fixing any damage caused to the property itself. If you try and fix any damage to the property before fixing the cause of the subsidence, it’s extremely likely that cracks will begin to reappear soon after cosmetic repairs are carried out.
3. Resin injections
Resin injections are a non-invasive and faster alternative to underpinning.
A number of small holes are drilled in and around the affected area. Resin is injected into each of the holes as a liquid and then expands, turning as solid as concrete. The hard resin compacts the soil and fills any voids.
Resin injections enhance the strength of the ground and can help raise, re-support and re-level foundations that had previously subsided.
This method can be carried out quickly (in as little as one day), with minimal disruption to the occupants of the home.
Underpinning is the most invasive, expensive and time-consuming treatment for subsidence. It is often recommended as a “last resort”.
Thankfully, the Royal Institution of Chartered Surveyors (RICS) estimate that less than 10% of properties suffering from subsidence need to be underpinned.
Underpinning can cost anywhere between £6,000 and £50,000, depending on the size of your property and the extent of the damage. Remember to also factor in the costs of alternative accommodation when the works are being carried out.
Most insurers will cover the cost, leaving you with just an excess to pay of around £1,000.
There are quite a few different types of underpinning methods. The three most common methods are:
- Mass concrete underpinning. This is the traditional method, where sections are excavated beneath the foundations of your home one at a time. The sections are then filled with concrete. This tends to be a long, disruptive process but can be effective for shallow foundations.
- Beam and base method. A reinforced concrete beam is constructed below, above or in replacement of the existing foundation. The beam then transfers the load of your house to mass concrete bases, which are constructed at designed strategic locations.
- Mini-pile method. “Piles” (metal or concrete shafts) are inserted into the ground through the weaker soil to a level of bedrock or firmer soil that can support the weight of your home more efficiently. This method involves no excavation, and so is the least disruptive of the three methods.
The choice of method appropriate for your case will depend on the ground conditions and the required foundation depth. Your structural engineer should be able to recommend the treatment plan that’s right for you.
Process for fixing subsidence
Unfortunately, getting a subsidence issue fixed isn’t as simple as contacting your insurance company and asking them to sort it.
There are multiple steps you’ll need to take before you get the paperwork confirming your property is structurally sound.
We have set out each of the steps below that you’ll need to follow to fix subsidence:
- Engage your insurer. You should inform your insurer as soon as you spot signs of subsidence. Your insurer will arrange for a qualified structural engineer to visit your property.
- Get an expert assessment. The structural engineer will carry out an inspection and prepare a report on their findings. The report will contain the diagnosis, the cause of the subsidence and their suggested treatment plan.
- Monitoring period (only required in certain cases). If subsidence is suspected, the structural engineer may need to carry out further investigations to find out the cause of the damage. This may include a period of monitoring (which can be as long as 12 months) to determine whether the building is moving.
- Obtain quotes from contractors. The next step will be to gather quotes from contractors and submit them to your insurer for approval. Your insurer may do this on your behalf and will use their approved suppliers.
- Get insurer’s authority to proceed. Once the insurance company has processed the quotes, they should then give you their authority to proceed with the repair works.
- Carry out repairs. Once you have your insurer’s authority to proceed, the repair works can be carried out at your property. The time it takes to complete the works will depend on the severity of the subsidence, the size of the area affected, and the extent of the repairs required.
- Get a Certificate of Structural Adequacy. This certificate is issued following completion of repairs and a monitoring period by a structural engineer. The certificate, among other things, contains a statement confirming the affected part of the property is now structurally sound. A Completion Certificate will also be issued by the Council if underpinning has been carried out.
The actual building work needed to fix subsidence can take as long as 6 weeks, or as little as two days. BUT, the entire process can take over a year to resolve when you include the time waiting on structural reports, gathering building quotes and negotiating with your insurance company.
Try and adopt a patient mindset and set your expectations accordingly.
Can you sell a house with subsidence?
You can sell a property with subsidence, even if it’s ongoing, but it can be trickier and more time consuming than selling a problem-free property.
It may be tempting to have any subsidence problems repaired before going to market, in the hope of attracting a wider range of buyers.
However, there is no guarantee that this strategy will produce a buyer or increase your property asking price.
For many people, your best option could be selling by auction. Auction can offer a faster and more certain sale, and potentially get you a better selling price.
To determine what the right fit for you is likely to be, take this short 60-second quiz I've designed.
By Matthew Cooper, Co-Founder of Home Selling Expert