What Exactly Is Resin Injection Underpinning?
When we talk to homeowners about resin injection underpinning one thing always comes up: “Is it really a long-term fix, or am I just putting off the inevitable?” Well, the truth is that resin can be a long-term solution but only if the root cause your house is subsiding in the first place is sorted out.
Geopolymer resin injection doesn’t just magically “fix subsidence”, it actually does something far more practical. It makes weak ground stronger and fills in gaps and holes beneath your foundations so that your house has something solid to stand on again. However, if the problem that’s causing your house to move (be it a leaky drain, a thirsty tree on stiff clay soil or just poor drainage in general), then these issues need addressing no method of underpinning – whether that be resin or traditional underpinning. So before we get to choosing the right tool for the job, we first sit down with you and work out what’s actually going on.
How Resin Injection Works Its Magic
Resin injection works by drilling tiny holes in or right next to your foundations and then injecting an expanding resin underneath. The resin then fills in all the gaps and strengthens the soil underneath your foundations. We’ve found on many projects that we can have the whole job done in a matter of hours – and that’s all while the homeowner is still living underfoot with minimal disruption – as opposed to the full-sized excavation you’d see with concrete underpinning.
What Exactly Do We Use In Resin Underpinning
Most geopolymer resin systems are a two-part expanding resin – the materials react and harden within the ground itself. They’re designed to be rock solid, water-resistant and just generally not bother the surrounding soil or fill in any way. For us as engineers though, the real question isn’t just what the product brochure says, but how the product actually behaves in your specific ground conditions.
When Do We Recommend Resin Over Traditional Underpinning
Geopolymer resin injection can be used in most situations. This might be a dropped corner in a Victorian terrace over in London, a bay window in Birmingham or that new extension you’ve put on in parts of Yorkshire and Wales. In most situations and ground conditions it is a perfectly acceptable way to stabilise the structure above.
Is Resin Injection Underpinning Really Permanent?
Homeowners almost always translate “permanent” into “I don’t ever want to think about this again.” And yeah, that makes a lot of sense – that’s how we engineers think about it too, when we’re designing a scheme. The resin itself is totally stable and doesn’t just degrade over time… but what really matters is whether the ground around it stays in the same condition it was in when we installed it.
How Long Can Resin Underpinning Really Last In Real-World Homes
When we’ve gone back to revisit properties years after we’ve worked on them and looked at the areas where we used resin, what we generally find is that they’ve remained stable as long as the underlying cause of the movement (like a leaky drain) was sorted out and the local drainage and vegetation was kept under control. It’s only when the underlying causes of the movement weren’t fixed – or new problems started developing in the surrounding area – that we started to see movement again. And that’s just the same as what happens with traditional underpinning – it’s not a matter of which method is better, it’s just which method fits your specific house and problems.
When Is Resin Likely To Be A Long-Term Solution
Geopolymer resin has the best chance of being a long-term solution when:
- You actually understand what’s causing your house to move in the first place.
- The area where you need to do the work is clearly defined and not spreading rapidly.
- The type of soil on your site is suitable for injection and expansion, which is most types of soils.
- Ground conditions that are subject to swell/heave or may contain voids or soft layers.
If all those conditions get ticked off, then we’re comfortable saying that resin can be a long-lasting, reliable option rather than just a temporary fix.
When Is Resin Probably Not The Right Fit
In most situations resin injection is a suitable solution. However there are some ground conditions where using it is more challenging, such as in peat or organic soils. In these cases, we look at design options using resin, or we will simply recommend other forms of stabilisation, such as traditional underpinning or piling. We will only recommend our solution if we feel that resin injection is suitable.
Resin Injection vs Traditional Underpinning
There’s a reason why people sometimes describe resin as “non-invasive underpinning” – but the truth is far more complicated than that. Both methods have their own place in the world… they just go about it in different ways.
How Much Disruption Do You Get With Each Method
Resin injection is usually much faster and less invasive. We can have a whole project done in a matter of days – without too much in the way of excavation – and with much smaller equipment on site. Traditional underpinning, on the other hand, involves digging all sorts of holes beneath your foundations, pouring in concrete in stages and taking a whole lot longer to get the job done. And on busy streets or where space is at a premium – the difference in disruption can be massive.
Costs – Resin vs Concrete Underpinning in the UK
Repair costs are all about access, how deep you have to dig, the extent of the work we need to do and just what else needs sorting out (drainage, monitoring, all that sort of thing). Check out our post on subsidence repair costs if you want to get an idea of what we’re talking about. You can also use our repair cost calculator to get a cost estimate.
What Can Affect Resin Underpinning’s Longevity?
The resin itself is just one part of the equation – it’s what’s around it that really matters. The ground and environment that the resin is in has just as much to say over how long it lasts as the resin itself does.
Soil Type – Chances of Movement with Clay, Made Ground & Fill
Clays, made ground and loose fill all behave in different ways when it comes to subsidence. We use different designs in different soil types to ensure that we get the right outcome every time. And if we can’t use our material, we tell you! You can use our postcode finder to see if your area is prone to subsidence issues.
Trees, Drains & Water Management
We take a close look at trees, shrubs, drains, gully positions and the overall water management in your area. If tree roots are sucking water out of drying clay or your drains are leaking into the structural soil, we’ll take that into consideration when coming up with your repair plan.
Importance of Proper Diagnosis & Monitoring
Sometimes we recommend monitoring crack movement or floor levels before and after work, especially on properties where we’re not entirely sure what’s going on. We’re not being paranoid here – it’s the only way to be certain what’s causing the problem and make sure the fix is working as expected. We can send out crack monitors to you, or we have a laser monitoring system called SubCheck which we can monitor remotely.
When to Choose Resin Injection, and When Not To
The truth is, resin isn’t a one-size-fits-all solution and any company that suggests it is, is overselling. There are too many factors to consider, however in most cases it is a vaible solution to stabilise soils and underpin foundations.
Signs that Resin Underpinning might be a Good Option for You
You might want to look into resin if you have:
- Localised movement in one corner, bay or side of your house.
- Limited access. We use 50m long hoses to take the material from the van to the injection point, meaning we can get down narrow passageways!
- Ground conditions that are subject to swell/heave or may contain voids or soft layers
Red Flags Where Other Methods Might be Better
We’ll tend to lean towards other methods if:
- You are in an area of peat or organic soils, although we can sometimes treat this
- You are in an area where there has been infills such as quarries or mines
Getting a Real Quote for a UK Subsidence Repair
A site-specific engineer’s assessment will always be better than any generic advice you find online. Contact Us if you’d like to get advice, a quote or arrange a site visit.
FAQs – Resin Injection Underpinning
Is resin injection a permanent fix for subsidence?
It can be long-lasting if you sort out the underlying cause of movement and the ground conditions suit the method. But no solution is going to last if the root problem isn’t fixed.
How long does resin underpinning last in UK soil conditions?
We tend to expect well-designed resin solutions to last for many years, providing you keep on top of things like drainage and vegetation around the property. We provide a warranty for our works.
Is resin underpinning safe for older properties?
Yes, if it’s done properly – that means proper design and installation. We regularly use resin on older brick and stone properties where access is a problem. We have even treated listed buildings!
Can resin injection be used on just one side of the house?
Yes, localised treatment is pretty common, but we’ll still take into account how that affects the rest of the structure and sometimes have to treat a wider area to ensure stability.
Is resin injection cheaper than traditional underpinning?
It is almost always cheaper to use resin injection. Labour and reinstatement costs are lower, but we can only give you a proper answer after we’ve taken a closer look at your property.
Does resin injection work on clay soil?
Yes, it can, but some clays have a high volume potential and shrink/swell – we will discuss this with you and explain how our material can help to mitigate this movement.
Will my insurer accept resin injection as a subsidence repair?
Most insurers will, provided it’s been properly designed and supervised by the right kind of professionals. Insurance claims will tend to take some time to manifest themselves and some insurers do not provide cover for subsidence.
How much disruption can you expect with resin injection compared to mass concrete underpinning?
It’s usually a lot less: fewer excavations, shorter programmes and less need to vacate the property.
CEO of Subsidence Ltd
