The scenario of clay-shrinkage subsidence returning a few years after it has been (supposedly adequately) mitigated and repaired is unfortunately all too common. This is usually because inadequate tree management had been carried out in the first place and roots have again caused cracks to appear through newly-reinstated finishes a few years down the line. Invariably the insurer then declares this a “new” episode of subsidence, and deals with the matter as a separate claim, applying another policy excess. Multiple subsidence claims are a huge red flag to underwriters who will often hike premiums in such circumstances or even withdraw subsidence cover altogether because of what they perceive to be an increased subsidence risk (see our separate blog on this here). A single subsidence claim which does not repeat on the other hand is not so concerning to them as the assumption is often that it was a one-off event that was properly resolved.
So when should a subsidence episode be classed as as “finished”? Structural monitoring is often continued after mitigation (i.e. vegetation management) as a check to make sure the property has stabilised before proceeding with structural crack repairs. We find that all too often however, this monitoring is interpreted as showing stability, whereas in actual fact low-level seasonal movement is continuing due to the ongoing presence of roots below the foundation during a cooler subsequent summer period. Buildings with shallow foundations on clay might move very slightly seasonally anyway (even without roots beneath), but this level of movement should not be enough to cause cracking. All too often we find that one or two trees are removed, but others (perhaps ones not identified as present beneath the foundations in the initial investigation) are left remaining, and these cause continued subsidence. That subsidence might be at very low level during a cool wet summer, but increase to a more obvious level during the next hot summer.
This scenario is very common and was the situation in a case heard by the Financial Ombudsman recently (Mr & Mrs S v AXA), when subsidence cracking appeared in exactly the same place 4 years after the original cracking was repaired. Monitoring after the initial vegetation mitigation had been done had (allegedly) shown stability, encouraging the insurer to declare the matter resolved and proceed to crack repairs and redecorations. The FO decided that it was unfair for AXA to treat this is a new and separate incident, and should not have applied a second excess, and that the additional premium applied due to a double subsidence claim was also unfair, and that AXA had not provided “a lasting and effective repair“. The full decision can be read here; https://www.financial-ombudsman.org.uk/decision/DRN-3916154.pdf.
So it is very important to ensure that if subsidence occurs, it is properly mitigated (i.e. with adequate vegetation management or alternatively an engineered solution) before repairs are undertaken. We advise our clients to seek an undertaking from their insurer (before agreeing to a settlement of their claim) that subsidence cover will be continued on reasonable terms (as per ABI Guidelines) and if further subsidence were to occur in the same area of the building due to the same cause (i.e. root-induced clay shrinkage – regardless of what vegetation it is deemed to be from), within a period of 5 (or even better 10) years from completion of repairs, that it should be treated as a continuation of the original subsidence claim and no further excess applied or new claim recorded. Insurers will often agree to this (albeit sometimes after some negotiation or dialogue – and when the above Ombudsman decision is pointed out to them).
Clearly different trees can grow up around buildings and cause similar problems further down the line, and it is right that these are treated as completely new and separate episodes. However, hot dry summers are clearly on the increase with climate change and no longer abnormal events – they should be expected to occur with increasing frequency and mitigation should be made accordingly. It is important that vegetation management around buildings on clay sites (including third-party vegetation) is an ongoing regularly-checked precaution which prudent homeowners should be making to try and avoid subsidence occurring in the first place. Clay shrinkage subsidence is an avoidable problem. If you are uncertain as to what vegetation constitutes a risk, you can seek a professional risk-assessment or vegetation management plan from an Arboricultural Consultant.
Bob Gibson – Subsidence Consultant