If you live in the South East, you could be in for a nasty shock. Without exception, the South East has one of the highest rates of subsidence in the UK. That means that all across the South, our homes and business premises could be slowly sinking into the ground. Surveys have stated that 1 out of every 5 homes in the South will subside, so the question is, what is subsidence and how can you take steps to prevent it happening to your house?
What is Subsidence?
Subsidence is something that any homeowner or property owner should be aware of, even if it’s never happened to you. Simply put, subsidence is what we call the gradual caving in or sinking of an area of land, and if your house is built on that area of land, it is more at risk of sinking with it. Subsidence usually occurs when the ground loses moisture, causing it to shrink and collapse. This can be caused by a number of things, but the top 2 causes are:
- Trees and shrubs that absorb significant volumes of water, causing dryness in the soil.
- Drainage problems.
But in the South East, there is one more thing to be aware of. If you take a look at this map (which documents cases of subsidence across the UK) you will see that there is a large cluster of red on the south east of the country. These red areas show ‘hotspots’, and was designed to help people identify problem areas. The South East is one big hotspot, mainly thanks to the high clay content of our soil. Clay based soil like ours is considered a ‘cohesive’ soil, which means that the volume will vary depending on the moisture, and the soil will shrink when dry and be washed away easily. 75% of UK ground subsidence cases are caused by soil shrinkage or washing, with hotspot areas most at risk. Many of these hotspot areas contain high levels of clay based soils, which are particularly vulnerable as they shrink and swell in relation to their moisture content. So in short, if you live in London or the South East, you need to be thinking about subsidence risk and how you can try to prevent it.
What’s Drainage Got to Do With It?
I’m going to be upfront here and say that there is no 100% fool proof way to prevent subsidence. But there are a few things you can do to minimise the risk of subsidence to your property – mainly properly maintaining trees and shrubs (which are the cause of 75% of subsidence claims) and getting your drainage sorted. Pollarding or the removal of trees and shrubs will stop them draining the soil of water, allowing more of it to remain in the soil. However, before doing this you should consult an arboriculturalist as the indiscriminate removal of all trees and shrubs might cause something known as ‘heave’. This is when the ground moves upwards due to rehydration, and that can cause its own set of problems. Also, some trees may be under Tree Preservation Order (TPO), in which case you will have to seek permission from the local authority before removing or pollarding any of them.
If you don’t have any trees around you, then you need to focus on your drainage systems. The second biggest cause of accelerated subsidence is water escaping from your drains before it reaches its destination. While this might sound like a good thing (after all, you want to keep the soil moist so that it doesn’t shrink and move, right?), the effect leaking drains has is to soften and even wash away the ground beneath your house’s foundations, causing the soil to sink and your house along with it. Water damage like this can also weaken the soil structure and the very foundations of your house, all of which add up to that tell-tale lean and a very expensive underpinning job. To ensure this doesn’t happen to you, you need to make sure all of your drains have been inspected for damage, leaks and cracks. This way you can catch them before they have a chance to really impact the soil underneath your house, reducing the risk of subsidence.
If you’ve noticed any signs of subsidence in your home, or your drains just need inspecting, ask a buildings expert like Bluehouse Drainage to help. Our team can inspect your current drainage systems for damage, and if they find anything, can recommend and install a complete and robust drainage solution. For more information, get in touch with the team today on 01923 281124.