Causes of Cracking in Buildings

Causes of Cracking in Buildings

I recently got a call from a man with cracks in his house.

He has built a rather nice two story house in North Denpasar on land which was, until fairly recently, rice paddies. Hairline cracks were visible in several rooms but at the back corner of the house was a major crack 3 cms wide rising 4 metres up the corner of the house. The back garden wall was tearing the corner off his house! Good for ventilation but not conducive for a good night’s sleep.

He didn’t think so but in fact he was relatively lucky. Next door and behind his house were two more houses each with a large crack right through the middle. Rather handy if you have a divorce in the family and you need to split the assets but these were new houses, brand new, fresh out of the box so to speak.

A local builder’s response was predictable. “No what what” (tidak apa apa) a bit of chewing gum and paint and no one will know the difference. Rather scary.

The cause of the problem was that the land the houses were built on is an area of old paddy fields with a good thick layer of mud. The mud expands and contracts between the wet and the dry season. Combine this with the weight of my friend’s concrete palace (English men always like to build things well don’t they, I suspect it is their way of being remembered in centuries to come) and it isn’t surprising he has cracks.

What causes cracks in buildings?

To anyone considering the major investment of building or buying a property in Bali it may be useful to know what causes cracks in buildings and how you may safeguard your interests.Have a look around, do you have cracks in your walls? Now before you go putting on your brown trousers it is important to understand that it is a simple fact of life that new buildings crack. We all live with cracks in our houses.

Land settlement

Cracks may be caused by drying out of building materials but is more usually caused by settling of the land as a result of the addition of the considerable weight of the building. If the house is properly built it is to be expected that such cracking would be minor and, unless you get the odd small earth tremor, would cease after a year or so.

There are two key questions to be investigated:

1. Are there cracks in the structurally important parts of your house such as reinforced columns, beams or suspended concrete floors?

2. Are the cracks still moving?

If the answer to both questions is no then cracks can usually be filled and painted over.

If, on the other hand, there are cracks in the main structural elements you should seek specialist advice from someone who understands the fundamentals of how reinforced concrete works and, more importantly, the vital aspects of how reinforced concrete should be repaired.

If cracks are still active and continue to appear or get wider or if they are more than “hairline” cracks then we have to consider more serious land movement than mere settling of the site.

Land Subsidence

In some countries land subsidence can be a problem as a result of mining operations. Coal or other minerals are removed leaving a void deep below the surface, the land eventually collapses and this may cause severe damage to buildings above.

In Bali we can probably forget land subsidence, there is not a lot of coal mining going on. In the more steeply sloping areas of Bali there are major problems with landslides. In many places paddy fields have been “sculptured” into the hillsides with steep slopes between them. If it rains a lot or a watercourse gets diverted onto the land it may well collapse.

Loss of Trees

Trees are very effective in stabilising the ground. The removal of trees in many parts of Indonesia has considerably increased the incidence of landslides. This is also a serious problem in Bali. I get into the countryside a lot and it is noticeable that the insatiable demand for carving wood has meant the quite worrying loss of treecover and land stability on the Island.

Landslips

In Bali landslips are very common on higher sloping land. Usually caused by heavy rain or where streams have eroded land or, believe it or not, where someone starts digging out soil from the block next door. I saw a block of land once where the landowner had dug soil out to a depth of 4 metres right up to the boundary wall. Great to have a neighbour like that!

Earthquakes

There are, of course, other causes of cracks in buildings.... earthquakes for instance. We do get earthquakes in Bali from time to time and there is always the potential for a big one. Don’t be scared of this – just be prepared. There are some very clear lessons to be learned from the Yogya earthquake and I will look at these another time. For the time being all we need to understand is that your house should be well designed by someone who knows what they are doing.

When you engage an architect check his credentials and ask him about previous work he has done.

Unfortunately it is important in Bali to either think for yourself or find someone you can trust. Either way if you want to build a house that will not fall down around your ears the next time you get the tremours I suggest you:

1. Select a stable building site.

2. Avoid steep slopes in the paddy fields (a nice dream I know)

3. Keep the structure light and if possible single story.

4. If you do want to build a concrete multistory house make sure it is properly designed and well built with reinforced concrete beams and columns. Concrete beams should also form part of the foundation.

5. Make sure that the foundation is strong enough for the design you choose.