Types of Cracks in load bearing walls | How to measure cracks | Causes of cracks

We can classify the masonry walls of a building into two types. The first type is the load-bearing walls of a building in which all the loads are carried down to the foundation through the walls. The second type of wall is the walls in reinforced concrete framed buildings or partition walls where the walls are designed as filler walls and not as load-bearing walls. In this article, we deal mainly with some of the causes of cracks in load-bearing walls. We also briefly discuss the filler walls.

 

Cracks in Load Bearing Walls

The main walls in buildings are usually 11/2 brick or one brick walls in thickness (Partition walls can be even half-brick walls.) The cracks in buildings (both in masonry and concrete works) are classified as follows according to the width of the cracks:

1. Less than 1 mm cracks are called thin cracks.

2. 1 mm to 2 mm cracks are medium cracks.

3. 2 mm to 4 mm cracks are wide cracks.

4. More than 4 mm cracks are very wide cracks.

 

Measurement of Cracks

When we see any crack in a structure, we show our interest in its size and try to find out whether it is an active (growing) crack or a passive (does not become bigger with time) crack. The size of a crack (or crack width) is measured by means of a crack gauge. There are different types of gauges. One type is shown in the Figure below. This type of crack gauge has different widths marked on it. We measure crack width by comparing the crack width with the different sizes marked in the scale and thus, find the size.

 

Crack gauge.

To find out whether it is an active or passive crack, we measure the crack with the passing of time by using the crack gauge or glass strip technique, as shown in the glass strip is pasted normally to the crack. It breaks if the crack is active.

 

Measurement of the progress of cracks (a) glass tell-tale for observing movements of cracks and (b) glass tell-tale for measuring movements of cracks.

 

Causes of Cracks

The first step in the treatment of cracks is to find their cause after which it is easy to treat the cause and then, repair the cracks.

Some of the reasons for the formation of a crack in a load-bearing wall can be one or more of the following reasons:

1. Defective rendering and plastering (shrinkage cracks)

2. Settlement of the foundation in a load-bearing wall or other settlement in the wall

3. Temperature effects

4. Local deformation at junctions of masonry with concrete members like concrete slabs bearing on masonry walls.

5. Cracks in half brick partition walls.

Some of these causes along with their remedies are briefly explained in the subsequent articles.