The removal of trees can also cause ground heave, which is why trees that are too close to the property should be taken down in stages, slowly over a number of years to allow gradual ground movement. If the clay becomes waterlogged it can expand and push the foundations upwards causing the cracks. On older properties with shallow foundations the clay can expand and contract dependent upon the weather conditions. The most common cause of ground heave is expansion of clay subsoils. The pattern of crack is similar to subsidence crack, however, the crack will be widest at the base of the wall. However, specialist advice from a structural engineer will be required. This will normally involve some form of underpinning. The cracks are normally the first indication of a problem often they are raking cracks (widest at the top) and can occur to corners of the building or from the top to the bottom of the walls. The list is endless however, the basic problem is the same the foundations of the house are moving. Subsidence can occur due to a variety of reasons: This is the worst and most serious type of cracks in masonry walls and consequently the most difficult to repair. Repointing and removal of the existing ties is recommended.Ĥ. Without replacement, collapse of the wall could occur. The cracking is an early indication of failure. When the metal ties rust they expand causing the cracking normally seen every sixth course horizontally in the mortar joints. Failure normally occurs when the ties rust. 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 inside. Cracks in Masonry Wall due to Tie Failure New lintels need to be installed and the cracks repaired.ģ. In some properties no lintels are provided relying on the timber frame of the window to support the masonry above, but once the window is replaced the cracks occur. The severity and age of these cracks would decide whether simple repointing would suffice until the window is replaced.Ĭause-4: Cracks in Masonry Wall due to No Lintels Once again replacement of the lintel is recommended. The load imposed is too great for the lintel to cope with and the downward pressure causes the cracking. This often occurs above first floor lintels where the roof purlins have been installed directly above the window openings. However, once again repointing will suffice until the window or door is replaced.Ĭause-3:Cracks due to loads applied above the opening Replacement of the lintel is recommended. Repair of Cracks due to Inadequate Bearing If the bearings are insufficient the lintel will drop and the cracks will appear. The correct overhang (bearing) of the lintels above openings is 150mm (6 inches) each side. However, collapse of the brickwork above the opening will be likely when the window is next replaced.Ĭause-2: Cracks due to Inadequate Bearings The poor repair is to do nothing more than repoint the cracks, as the brickwork is now resting on the new frame. The best repair is to reset the lintel and repoint or rebuild the brickwork above, and refit the window. The most common reason for this type of cracks in wall is the removal of existing window frames to install PVCu. Loads applied directly over the opening,Ĭause-1: Removal of windows or doors with inadequate propping.Removal of windows or doors with inadequate propping,.Cracks Above Openings in Masonry Walls Causesįour causes of cracks above openings in masonry walls are: On some modern buildings these are formed at construction stage and then hidden behind rainwater downpipes.Ģ. This would be cut into the wall, filled with a compressible material with a waterproof stopper to the outside. However, for more severe cracking it is advisable to form an expansion joint. Therefore filling the crack with a mastic or sealastic compound is recommended. This type of crack has a consistent width and it is this that distinguishes from other more serious cracks.Įxpansive crack is of no real structural significance, although it may allow water into the cavity in brick built houses, and subsequence cause deterioration of the wall ties. The expansive cracks are often seen above window and door openings where the opening itself relieves the crack.
0 Comments
Leave a Reply. |