An article about " AVOID CRACKS IN BUILDINGS "

AVOID CRACKS IN BUILDINGS

Often people complain of cracks on walls after plastering works. Plastering plays an important role in the construction of a building. Just as skin gives shape and texture to the body and protects it from the harmful environment, plaster protects the building from damage caused by salts, acid and rain in the external environment. It also makes the building look beautiful and attractive.

Defect free durable plaster, free from cracks or other defects can be achieved by diligently following the correct construction practices.

One of the reasons cited for cracks is lack of proper cement sand ratio. Normally, for outside plaster, the cement-sand ratio can be from 1:4 to 1:5, for internal plaster from 1:5 to 1:6 and for roof plaster from 1:3 to 1:4.

For better results, check that the mason uses a 1:4 rations mortar of cement and fine sand. For coarse sand, the ratio can be changed to 1:6. However 1:4 mixes is preferred for best results. Make sure that the mason has not prepared the mix all together for the whole day. The mix must be prepared only in small quantities so that it is used within an hour. If excess mortar is prepared, it dries up due to evaporation and remixing deteriorates strength and increases porosity.

The risk of crazing cracks may be minimized by the use of relatively weak mix for finishing coat, avoiding excessive proportion of very fine material in the finish coat and avoiding excessive toweling so as to prevent the excess of laitance drawing to the surface. A major precautionary measure to be under taken prior to plastering is remove loose mortar and grease from joints. All joints in the masonry should be raked out to a depth of a least 12 mm with a hooked tool made for the purpose while the mortar is still green and not later than 48 hours of the time of laying. Another important task is that the wall should be wetted for a few hours. The walls should not be soaked but only dampened evenly. Plastering on wet walls is seldom satisfactory because key is not formed between the plaster and the background surface. A good key is essential for successful rendering and for avoiding cracking and crazing. In an ideal state the background should be in saturated surface dry condition.

Addition of water should be carefully monitored. Excess water will cause shrinkage as well as low strength of plaster. Waterproof compounds if used should be uniformly dispersed and mixed properly.

When plastering is done in two coats, the first coat should be left rough and open from edge of the laying trowel and after it has been left long enough to set firm, the surface should be combed or scratched to form a key for the second coat. The first coat should be allowed to dry for three to five days before subsequent coats are applied.

Use a chicken wire mesh while plastering joints between the concrete work and brick-work. Plaster should be finished with a wood felt. A steel trowel shall not be used. Ensure continuous curing for 10 to 14 days. You may keep in mind that the need for repairs arises due to negligence, use of unsuitable materials and improper construction practices. Therefore, to save your buildings from cracking adopt proper construction practices.