cracks in buildings,http://sandra-markle.blogspot.my/2011/03/writing-docudramaspart-one-i-survived.html
How to solve the Cracks in the Buildings
Cracks are common in buildings, one should not be alarmed to see cracks on the walls but sit back get the help by following these steps.
Cracks can be classified as active or dormant. Active cracks tend to get larger and changes with time. Dormant cracks are those have settled and need no alarm , are of no danger, but should be not left not repaired as moisture penetration may cause further damages.
Cracks may be classified as structural cracks or non structural crack. If it is structural cracks, one has to take immediate actions to rectify the cracks and if it non structural cracks, you need to touch up the cracks. On may recognize the structural crack by the direction of the cracks.
Cracks can also be classified by 1) direction 2) width, and 3) depth of the crack. They may be longitudinal, transverse, vertical, diagonal or random. They may range in size from less than 1 mm (fine) to between 1 and 2 mm (medium) to over 2 mm (wide).
The following are some of the types of crack occurring in concrete:
1. Pattern Cracks: Fine openings in regular arrangements which due to inconsistent volume of concrete which is lower near the surface.
2. Checking cracks: Small openings which are closely and irregular direction and space .
3. D-Cracks: Fine cracks at close intervals in a progression with random pattern.
4. Shrinkage cracking: Crack in unhardened concrete, which are straight lines parallel to each other.
5.Plastic cracking: Crack in unhardened concrete, appearing as diagonal lines in the top of a slab, caused by rapid drying of the concrete surface when curing additives are added.
6.Settlement cracksCaused by local restraining around re-bar.
7.Structural cracks:Cracks that are a result of corrosion of the re-bar or structural over stressing or due to under designing of load.
8. Tension cracks: Cracks which appear in concrete which are caused by the stretching of the reinforcement which are subjected to tension.
9.Rust cracks: A serious cause of structural cracks caused by insufficient rebar cover. The cover may crack off and the exposed rebar are subjected to rust.
10.Thermally-induced cracks: Cracks appearing from stresses created by the diurnal of temperature changes over the day or seasonal.
11.Hairline Cracks: Small cracks and fine crack lines that are randomly placed.
structural cracks that needs to be resolved
Cracks in brick walls(CP 111)
Cracks found in 215mm thick brick walls by more than 25mm wide in a stepped or slanting cracks are not a concern as invariably it is deem to carry the load, as shown in test at the Building Research Establishment in England( provided it was not accompanied by considerable transverse movement). Also note the strength of a cavity wall is approximately 20% less that that of a 215mm brick wall.
The reasons for cracks in brick walls may be:
changes in ground conditions,
inadequate consolidation of ground,
shrinkage-able clay,
fast growing trees,
unsound materials(brick, mortar joints)
frost
|corrosion of iron and steel,
shringakage and expansion of walls during cold and hot seasons,
climbers, ivy , climbing rose, morning glory,etc., may cause damage to the walls,
mining subsidence of the foundations.
Cracks, of 1.5 to3.5mm wide are called fine cracks and need to be repaired but has not structural impairment, the repair may be replace the brick or fill it with mortar(1:1:6)pointing and refinish with wall paper or paint etc.
Structural cracks
Structural cracks are large cracks and will be either vertical lines or 45 degrees line cracks or any cracks that runs between the vertical lines to the 45 degree line. Structural cracks are further characterized by the cracks where you can place your finger (when you can insert a large coin) within the crack lines. Further more these cracks would crack the structural member of the building, such as the beams, columns, lintels etc
Diagonal cracks- almost always are structural in nature
Minor cracks are hairline cracks which are superficial that have no structural members are affected by the cracks. A quick check can be done by hacking the plastered surfaces or the rendered surfaces and check if the cracks are merely superficial on the plaster or rendered surfaces or it has affected the walls within and the structural members, if the structural members are cracked, than you need to find out if it a hair line crack or deep cracks that affects the structural integrity of the structure has been affected.
Hairline cracks in structure and on finished surfaces are acceptable and sometimes beyond the means to control them. Hairline cracks on structural members are considered normal, it may be caused by the heat that is caused by concrete when it is curing at the construction stages.
Hairline cracks on finishes may be due to the cooling ( air conditioning)and heating during the mid day may causes it, and fissure cracks appear is considered quite normal. It may be caused by an incorrect mix of cement and sand in the plastering and rendering during constructions or excessive exposure to the hot sun, in case the walls should have been constructed with expansion joints and movement joints to reduce these cracks
Hairline cracks
The mere size of the crack as described in the above para will decide the seriousness of the problems.
hairline cracks, a minor concern
Minor cracks should be repaired and observed for further development of crack.
Step 1 in the Buildings
Identify the causation of crack to solve, this is necessary so as to avoid redundancy of rectification, and this will avoid a repetition of cracks even after the rectification of cracks were carried out. Cracks and the following may be the causation or reasons of the structural cracks.
- The causes of structural cracks may be due to the foundation may have been under designing of the structure .
- The structure may have not been built structurally sound and the failures in the beams or columns may be the cause of the cracks. These may even so for cracks in drains, walls, roof slabs or ground floor slabs.The shoddy supervision of work or the lack of materials compliance as per the specification may have been short changed
- There may be s sudden shifting in ground conditions such as shifting of underground streams, which may result in creating a vacuum, causing earth to collapse and thereby affecting the buildings ground structure.
- there may be due to vegetation or trees in the close neighborhood which roots may cause the house to be lifted up or the absorption of water by the roots may cause building lift
- The supervision of the ground compaction may have not been done correctly; this may results in cracks in the ground, beams and roads.Poor compaction of ground or earth sub grade or sub grade of the road may cause cracking, the sub grade should be compacted to 90-95% FDT( Field Density Test). non suspended ground floor slabs may also cracks due to lack of sufficient compaction, often the apron of a building may be seen to cracking cos of lack of sufficient defective compaction.
cracks on the road winter quakes
The cracks may appear due to differential compression and expansion of the building m such as walls or road, the wall need to provided with expansion joints to allow for the expansions so that cracks are minimized, in colder countries such as Wisconsin the roads are often cracked due to these reason, Provisions for expansion should be provided to reduce these cracks during the winter seasonal quakes.
measuring cracks for increasing width of crack size
Step 2 to solve the Cracks in the Buildings
Monitor the increase of the crack size, and note the changes in the crack width. if the crack width is increasing. if it increasing in size , call the engineers to review the conditions. if the crack size is constant and you are safe to conclude the night mare is over and you can rectify it and sleep soundly.
Step 3 to solve the Cracks in the Buildings
If the cracks are large and getting serious large and looks dangerous, get the advice of engineersA structural Engineer need to be called in, for inspection and for his advice should be sought on the nature of cracks and advice on the course of rectification action.Take the follow steps to resolve the cracks in your home.
Step 4 to solve the Cracks in the Buildings
Repair the major cracks and minor cracksThe existing cracks are be grooved widen along the crack line and filled up with a suitable sealant and closed up with fabrics mesh and plastered and repainted. A simpler method to repair hairline cracks is to fill it up with a filler and repaint the surfaces or redo the finishes of possible.
Step 5 to solve the Cracks in the Buildings
Watch out for the re occurrence of cracks, if the cracks appears, you need to evaluate the situation for reasons for these phenomenon.On repairing the cracks should be monitored for any cracks redeveloping in the future.
Prepared by Architect Perumal Nagapushnam,Eco Green Architect & Net Zero Energy Architect
