How to Spot and Prevent Dangerous Structural Issues

Monday, July 18, 2016

Uneven Ground

Subsidence is the vertical downward movement of a building foundation, often caused by poor quality or eroded ground beneath, which I write about in more detail here. This causes the entire house or – more dangerously – a section of the house to sink into the ground, damaging the structure.

The most obvious symptom of subsidence is asymmetry, usually most visible in sloping or tilted window heads. A wonky house means that the forces of gravity are not being distributed as they were originally intended, or if the subsidence is uneven, more extreme in one section of the house than another – which can slowly tear your house apart.

Another common and worrying sign that there may be a subsidence problem are long, vertical or diagonal cracks in the exterior brickwork or interior walls caused by one part of the house slowly moving away from the other.

A sticking door or window can also be a sign of subsidence. If the house has sunk or tilted, then the door or window frame may have shifted out of its original shape, while the door or window itself has remained a perfect rectangle. It simply no longer fits, and becomes difficult to open and close.

Subsidence may be solved with foundation works such as underpinning, which is a slow process of excavating beneath the foundations of a house section by section and filling it with concrete.

Forces of Nature

A leaky roof is incredibly unpleasant, and undermines the feeling of safety and shelter that a home should give. If you’re lucky, the leak will be obvious, letting you quickly take action to repair the source of the leak, usually lost or damaged roof tiles.

More dangerous are hidden leaks that allow damp to slowly accumulate in the timber without you knowing, causing the growth of a wood eating fungus called wet rot. Even worse is dry rot, which is more aggressive and usually requires complete replacement of the timber.

Timber can also become infested with woodboring beetles who riddle the timber with thousands of tiny holes which, like wet and dry rot, gradually weakens the timber. If caught early enough, the timber can be saved by pumping the house full of a deeply unpleasant insecticide.

Moving on to the outside, rain and freeze-thaw can erode mortar, the adhesive paste which holds bricks together. Eroded mortar significantly weakens brick walls, which needs to be addressed if you’re going to do any building works. In some old houses, the walls become so weak that you can push them over once the roof is removed.

An easy to way to test the strength of the mortar is to take a knife and scrape it along the mortar. If it crumbles away easily, then the wall needs to be repointed. Luckily, a good repointing job should last 50 or more years, so it’s only something you should have to worry about once a lifetime.

The Ghosts of Cowboy Builders

Very few period homes have remained identical in structure throughout their life. When you buy a period property, you’re also buying the years of alterations and improvements made by previous owners, some which may have been for the better, some for worse.

There’s always a risk with a period property that it’s haunted by the mistakes of cowboy builders from the past, who may have removed a load bearing wall or built an extension on unstable ground. Building regulations were not always as strict as they are now, so if you’re living in a period property or considering buying one, make sure you have it assessed by a structural engineer to identify any weak spots caused by shoddy building work.

If severe structural weaknesses are discovered, we may have to install supports such as lintels or steel beams to prop up floors and walls that are in danger of collapse, especially if we’re doing building works that will put additional stress on the structure.

Does Your Home Have Wrinkles or a Does it Have a Disease?

It’s worth noting that even if there is evidence that the structure of your house has shifted, it doesn’t necessarily mean that the structure is in danger. There is a degree of natural settling of materials over time which becomes more apparent the older the building. Some wonkiness is often part of the charm of period properties and when we work with old and especially listed buildings, preserving some imperfections can be essential to maintaining their character.

However, the line between charming imperfection and critically dangerous degeneration can be thin, and if you’re not qualified to tell the difference you simply cannot make a judgement. Our partnership with world class structural engineers such as Nigel Reynolds gives us the confidence to push our clients dreams to the limit while keeping their home safe through every step. If you want to put your home in the safest possible hands, click here to get in touch with us now.

John Dyer-Grimes