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Several types of cracks occur in masonry walls in a building which can be modest and insignificant, some requiring expensive repairs and in some extreme cases the just solution is total demolition of the wall. Causes of these cracks in masonry walls can be motility of building causing settlement and subsidence.

Contents:

  • Common Causes of Cracks in Masonry Walls
  • Types of Cracks in Masonry Walls and Causes
  • 1. Expansion Cracks in Masonry Wall
    • Causes of Expansive Cracks
    • Repair of Expansive Cracks
  • 2. Cracks Above Openings in Masonry Walls
    • Causes
    • Cause-1: Removal of windows or doors with inadequate propping
    • Repair of Cracks
    • Crusade-2: Cracks due to Inadequate Bearings
    • Repair of Cracks due to Inadequate Bearing
    • Crusade-3:Cracks due to loads applied above the opening
    • Repair
    • Crusade-4: Cracks in Masonry Wall due to No Lintels
    • Repair
  • iii. Cracks in Masonry Wall due to Tie Failure
    • Repair
  • 4. Cracks in Masonry Wall due to Subsidence
    • Repair of Cracks due to Subsidence
  • 5. Wall Cracks due to Ground Heave
    • Repair of Cracks due to Footing Heave

Mutual Causes of Cracks in Masonry Walls

Settlement and subsidence of edifice walls is shown in figure below.

Settlement and Subsidence of Masonry Wall

Fig.1: Settlement and Subsidence of Masonry Wall

Settlement of masonry wall occurs due to downward pressure from the loads on wall and subsidence occurs due to the removal of world beneath the foundations. Settlement is normally hands dealt with via cosmetic repair, whereas subsidence tin show hard and costly to repair. There is a situation where settlement of walls can crusade subsidence. If the drains continued to a building shear or scissure due to settlement, the subsequent leakage can cause subsidence by washing away the subsoil. All buildings settle when they are constructed; the trick is to keep the settlement to an infinitesimally low level. The other causes of movement and cracking are due to poor pattern, poor structure methods, or poor maintenance. For definition the diagrams are shown in brickwork; however cracks course in stonework in a similar fashion.

Cracks in Masonry Walls

Fig.2: Cracks in Masonry Walls

Types of Cracks in Masonry Walls and Causes

1. Expansion Cracks in Masonry Wall

Causes of Expansive Cracks

Walls are afflicted past temperature and moisture change. Materials can endure from initial shrinkage and/or subsequent expansion and wrinkle. This movement gives rise to the expansion cracks in masonry walls. The crack shown in the picture is shown as vertical, which is oftentimes the instance. Nonetheless, the crack sometimes follows the line of least resistance and can end up stepped.

Expansion Cracks in Masonry Wall

Fig.3: Expansion Cracks in Masonry Wall

The expansive cracks are oftentimes seen above window and door openings where the opening itself relieves the cleft. This type of scissure has a consistent width and it is this that distinguishes from other more serious cracks.

Repair of Expansive Cracks

Expansive crack is of no real structural significance, although it may let h2o into the crenel in brick built houses, and subsequence cause deterioration of the wall ties. Therefore filling the fissure with a mastic or sealastic chemical compound is recommended. However, for more severe cracking it is appropriate to course an expansion joint. This would be cutting into the wall, filled with a compressible cloth with a waterproof stopper to the exterior. On some modern buildings these are formed at construction stage and and so hidden behind rainwater downpipes.

2. Cracks Above Openings in Masonry Walls

Causes

Four causes of cracks in a higher place openings in masonry walls are:

  1. Removal of windows or doors with inadequate propping,
  2. Inadequate bearings,
  3. Loads applied direct over the opening,
  4. No lintels.

Cause-1: Removal of windows or doors with inadequate propping

The most common reason for this type of cracks in wall is the removal of existing window frames to install PVCu.

Repair of Cracks

The best repair is to reset the lintel and repoint or rebuild the brickwork above, and refit the window. The poor repair is to do nothing more than repoint the cracks, as the brickwork is now resting on the new frame. However, collapse of the brickwork to a higher place the opening will be likely when the window is next replaced.

Cause-2: Cracks due to Inadequate Bearings

The correct overhang (bearing) of the lintels above openings is 150mm (6 inches) each side. If the bearings are bereft the lintel will drop and the cracks will appear.

Repair of Cracks due to Inadequate Bearing

Replacement of the lintel is recommended. However, once again repointing will suffice until the window or door is replaced.

Crusade-3:Cracks due to loads applied higher up the opening

This often occurs above start floor lintels where the roof purlins have been installed straight in a higher place the window openings. The load imposed is also great for the lintel to cope with and the downward pressure causes the bully.

Repair

Once again replacement of the lintel is recommended. The severity and age of these cracks would decide whether uncomplicated repointing would suffice until the window is replaced.

Cause-four: Cracks in Masonry Wall due to No Lintels

In some properties no lintels are provided relying on the timber frame of the window to support the masonry above, only in one case the window is replaced the cracks occur.

Repair

New lintels demand to be installed and the cracks repaired.

3. Cracks in Masonry Wall due to Tie Failure

Wall ties are metal ties that are built into both solid and cavity walls built in stretcher bond to hold the outside skin of brickwork to the within. Failure normally occurs when the ties rust. When the metal ties rust they aggrandize causing the smashing normally seen every sixth class horizontally in the mortar joints.

Repair

Replacement wall ties are essential. The bully is an early indication of failure. Without replacement, collapse of the wall could occur. Repointing and removal of the existing ties is recommended.

4. Cracks in Masonry Wall due to Subsidence

This is the worst and most serious type of cracks in masonry walls and consequently the most hard to repair. Subsidence can occur due to a diverseness of reasons:

  1. Mining action
  2. Leaking clandestine drainage
  3. Tree root activity
  4. Elevation subsoil
  5. Clay subsoil
  6. Running sand

The listing is endless; however, the basic problem is the same; the foundations of the house are moving. The cracks are ordinarily the outset indication of a problem; often they are raking cracks (widest at the peak) and tin can occur to corners of the building or from the meridian to the bottom of the walls.

Repair of Cracks due to Subsidence

This will usually involve some class of underpinning. Even so, specialist communication from a structural engineer will be required.

5. Wall Cracks due to Ground Heave

The pattern of crack is similar to subsidence crack, all the same, the crack will be widest at the base of the wall. The most common cause of ground heave is expansion of clay subsoils. On older backdrop with shallow foundations the dirt tin can expand and contract dependent upon the atmospheric condition conditions. If the clay becomes waterlogged it tin expand and push the foundations upwards causing the cracks. The removal of trees can also cause ground heave, which is why trees that are too close to the property should be taken downwardly in stages, slowly over a number of years to allow gradual footing movement.

Repair of Cracks due to Basis Boost

In extreme cases underpinning and/or deeper foundations will be the only solution. This is all the same, a drastic measure out. In cases of ground heave problems the solution volition be to remove as much of the clay from around the foundation as possible and to replace it with hardcore.