In 2003 I bought my first place in London and it needed to be completely renovated. Actually, let me rephrase that; it was the home equivalent of the Mary Rose with rotten timbers and structural cracks in the front and side-walls at high level that were large enough to put your hand into! It was so bad everyone suspected structural subsidence where the foundations of the house had been damaged. They also thought I was a lunatic for taking it on. But after digging a few inspection pits around the house I discovered that the foundations were perfect. It was the front wall pulling away from the sidewalls of the house caused the cracks.
This is ‘lateral movement’ and not subsidence. Ok, its still not great news and it would eventually cost me £30,000 to put right, but the damage looked so bad it enabled me to negotiate £150,000 off the asking price and get an absolute bargain. Not a bad days work.
The more you look at buildings and understand how they work you begin to see them as living, breathing animals. Ok, now I am sounding like a lunatic, but let me explain. Buildings like to breathe and have lots of fresh air in the summer so we ventilate them, they like to stay warm in the winter so we heat them, and they like to stay dry so we protect them, but surprisingly they also like to move. Most building materials expand and contract throughout the year due to changes in temperature. This is why its good to design in flexibility into the building by using things like flexible adhesive for your bathroom tiling or by installing expansion joints when you build a brick wall.
Your home can also move depending on the condition of the ground it is built on. In parts of Britain where homes are constructed on clay there can be a lot of ground movement between the summer, when it is warm and dry, and the winter when it is cold and wet. This ground movement can cause small cracks in the summer, which then close up again in the winter. There isn’t a lot you can do about this and it’s often nothing to worry about.
One of the most common structural problems I see in period homes is cracking around bay windows. This is often caused by the structure of the bay window pulling away from the main body of the house, which can easily be put right using structural ties to strap it back together, or more worryingly, by root damage caused by trees on the street. Tree roots are lethal to buildings and the only way you can put this damage right is to install a new concrete foundation.
If you find more substantial cracking to the outside of the building where the crack goes all the way down to ground level and down to the foundation then the alarm bells should start ringing. This is subsidence and the only way you can put this right is to underpin the property.
Underpinning is a process where you dig out lengths of the existing foundation and put a new concrete foundation under the existing wall. This is done in small stages so as not to undermine the structural integrity of the building. Although you may have heard the story about the multi-million pound house in Notting Hill that completely collapsed when the underpinning contractor dug out too much soil in one go! Underpinning can be a frightening and very expensive process. Make sure you use an approved underpinning contractor for any of this work. See the Association of specialist Underpinning Contractors at www.asuc.org.uk.
No matter how old your home is, or which area of the country you live in, make sure you are fully covered for subsidence on your building insurance because by the time you see the damage it is often too late. Good insurance helps you sleep at night.
If there are any large trees close to your house keep them trimmed back to minimise the spread of roots and if you see any substantial structural movement contact a structural engineer or surveyor. They will assess the damage and suggest the best course of action. See the Royal Institute of Chartered Surveyors at www.rics.org.
Remember all buildings like to move, but hopefully, not too much.
