Three Signs Of Subsidence And How To Fix It

Just hearing the word subsidence makes most house buyers run for the hills. But if you’re brave enough to take on a renovation project with suspected subsidence – or you think your home is suffering from it – then it’s important to know how to spot the signs and solve the problem. So, let’s take a look at house subsidence causes, symptoms and fixes. 

What is subsidence?

Subsidence is the structural movement of your home. It’s caused by the ground below being disturbed or by the ground sinking. Causes can be natural or due to the climate changing. Or it can be due to manmade interference. 

For example, some terraces in old industrial areas have mine shafts deep below the foundations. This means that the ground below isn’t solid and stable. But it can also be caused by water from persistent leaks moving or washing away the ground or by drains sinking or collapsing. Long spells of hot dry weather can dry out the ground, causing shrinkage and movement too. As can the roots of trees.

Diagonal cracks

Diagonal cracks are one of the most common signs of subsidence. They can appear outside and inside a house. Often, there’ll be a crack along the brickwork on the outside. This usually creates a visible gap in the mortar. Typically, the crack is diagonal, but vertical and horizontal cracks can sometimes appear too.

Inside a house, diagonal cracks can span the entire wall, from one corner to the other. But sometimes cracks travel from weak points such as a door frame, gable end or the brickwork joining an extension. These are very different from hairline cracks you frequently see in plaster. The gaps may be just 3 or 4mm wide, or they may be wide enough for you to put your hand inside. Either way, it’s a sign of subsidence and it can’t be ignored.

Sloping floors

If you’re looking at or walking on your floor and feel that it’s sloping, then you might be right. If your house is slowly sinking at one end or a drain has collapsed, then this can cause the floors to slope. An easy way to tell if a floor is really sloping is to put a ball down on it. If the ball rolls across the floor, then there’s definitely a slope.

Sometimes old buildings have wonky floors simply because of their age and it’s nothing sinister. So, look for other issues such as sticking doors, as this is a sign that the house has undergone some movement. But, if you’re in any doubt, call in an expert.

Wonky windows and doors

In fact, wonky windows and doors are a great tell-tale sign of subsidence in themselves. Subsidence cracking doesn’t just run diagonally from frames but it can actually detach a window or door frame from the wall, leaving an obvious gap. And this can cause the framework to warp out of shape.

Equally, when brickwork begins to sink or sag, window and door frames will too. So, your windows and doors can look wonky and can stop opening and closing properly. 

How to fix subsidence

The good news is that subsidence can be fixed. The cause and extent of your subsidence will determine the best way to remedy it. Subsidence repair costs could set you back as much as £36,000, but that’s only in extreme circumstances. Repairs to drains or the removal of trees will cost much less to fix. 

So, the first thing to do when you suspect your house has subsidence is to get it assessed by a structural engineer. They can confirm that the issues aren’t historic or merely settlement cracks. If it is indeed active subsidence, they’ll be able to advise you on the best course of action. 

If there has been substantial ground movement or the foundations are deemed inadequate, then it’s likely that underpinning is the way forward. This can involve the pouring in of concrete or the addition of piles to bolster the foundations. It’s often tricky and disruptive work, but it will solve the problem. If tree roots are the cause, then these will need removing too.

Drain issues such as a collapsed drain or water leak will need some investigation first. This may need a CCTV camera feeding through the pipes to confirm the cause. Then a drain or water pipe repair is needed.