Unit III Finishes in building use .pptx

This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior quality materials and defective workmanship and also provides a protective coating against atmospheric effects. It further provides a base for receiving other decorative finishes such as painting, white washing, etc.This is the process of covering various surfaces of the structure with a plastic material such as cement mortar, lime mortar or composite mortar, etc to obtain an even, smooth, regular, clean and durable surface. Plastering conceals inferior it's use .

1. Presented by : Ar. Pooja Joshi Unit III : FINISHES BCM-I First Year- BVDU College of Architecture, Pune

2. Plastering  is a process by which coarse surfaces of wall or ceiling roofs are changed or turned or rendered to provide smoothness. The prime purpose of plastering is to obtain hard and smooth surface that could be painted and provide nice aesthetic appearances. PLASTERING Objectives of Plastering : To protect the external surfaces against penetration of rain water and other atmospheric agencies. To give smooth surface in which dust and dirt cannot lodge. To give decorative effect. To protect surfaces against vermin. To conceal inferior materials or defective workmanship.

3. Lime Plaster Lime mixture consists of sand and lime that are mixed by 1 sand to 3 of lime by volume . Not only this mixture is used for under coat but also used as finish coat. Lime plaster might shrink after drying so animal hair of about 5 Kg is used for 1 m 2  to avoid lime plaster cracking and shrinking. Lime plaster could be used for ancient structure restoration and rehabilitation. Cement Plaster Grey powder Portland cement is mixed with water by the ratio of 1cement to 3 or 4 clean washed sand by volume as an under coat for hard background for example brick block walls and partitions. Mixture of sand and cement might be plastic and require experienced and skill labor therefore plasticizer or lime is added to the mixture usually by volume ratio of 1cement:0.25 lime: 3 sand or 1 cement to 4 sand with plasticizer. Plasticizer is a liquid that added to the mixture to ease plaster spreading over the surface. Types of Plaster based on Material Used

4. Gypsum Plaster Gypsum plaster is widely used plaster materials that could be mined naturally or produced as a by-product. Moreover, small expansion of gypsum is considered significant propertied that prevent shrinkages and cracks. There are various types of gypsum plaster that are produced by heating gypsum to a specific degree for example anhydrous gypsum manufactured by heating gypsum up to 170 C o , hemihydrates gypsum produced by heating gypsum more than 170 C o . Furthermore, depending on applications for walls or ceilings gypsum plasters can be categorized such as casting, undercoat, finish, one coat and machine applied plaster. Types of Plaster based on Material Used

5. Types of Plaster Finishes used in Building Construction are: Different types of plaster finishes with different appearances are available as follows. Smooth cast finish Rough cast finish Sand faced finish Pebble dash finish Scrapped finish Depeter finish Textured finish Smooth Cast Plaster Finish To obtain smooth cast finish, mortar used should be in the ratio 1: 3 [cement: sand]. Fine Sand should be taken to prepare the mortar. For spreading the mortar, skimming float or wood float is best suitable tool. Hence, smooth and leveled surface is obtained finally.

6. Rough Cast Plaster Finish Rough cast finish is also called as spatter dash finish. Mortar used to get rough cast finish consist coarse aggregate along with cement and sand. Their ratio is about 1: 1.5: 3. The size of coarse aggregate used is 3mm to 12mm. Large quantity of mortar is taken by trowel and it is dashed into the surface and levelled using wooden float. Usually this type of plaster finish is preferred for external renderings. Sand Faced Plaster Finish To get sand faced finish two coats of plastering is required. For first coat, 12mm thick layer of cement sand mortar in 1: 4 ratio is preferred. The first coat should be provided in zigzag lines. And then it is allowed for curing for 7days. After that 8mm thick layer of second coat with cement and sand in 1:1 ratio is applied. Level the surface using sponge. Finally take some sand and screened it to obtain uniform grain size. The screened sand is applied on the second coat using skimming float or wooden float. Finally, sand faced finish with uniform grain size of sand is obtained.

7. Pebble Dash Plaster Finish Pebble dash finish requires mortar layer of 12mm thickness cement and sand in the ratio of 1: 3 . After plastering pebbles of size 10mm to 20mm are dashed on to the plastered surface. Then pressed them into the plastered surface using wooden float slowly. After hardening they provide aesthetic appearance to the structure. Scrapped Plaster Finish To obtain scrapped finish, apply final coat of 6 to 12 mm thickness and allowed it to dry. After some time using steel blade or plate scrap the plastered layer up to 3mm depth. Scrapped finish is less liable to cracks.

8. Depeter Plaster Finish This is also similar to pebble dash finish. But in this case pieces of gravel or flints are used in place of pebbles. Textured Plaster Finish Textured finish is obtained from the stucco plastering in which different textures or shapes are made on the final coat using suitable tools. Requirements of god plaster : Its should adhere to the background and should remain adhered during all variations of the climatic changes. It should be hard and durable. It should be possible to apply it during all weather conditions. It should possess god workability.

9. The following defects may arise in plaster work : 1. Blistering of plastered surfaces : This is the formation of small patches of plaster swelling out beyond the plastered surface, arising out of late slaking of lime particles in the plaster. 2. Flaking: It is the formation of very loose mass of plastered surface, due to poor bond between successive coats. Cracking Defects in Plaster :

10. Efflorescence Caused due to presence of soluble in plaster Even water used in the construction work may contain soluble salts . Rust stains Rust stains are sometimes seen on the plastered surface especially when plaster is applied on metal lath . Uneven Surface Uneven surface defect becomes prominent only due to poor workmanship of the plastering work. Defects in Plaster :

11. The term Pointing in construction is applied to the finishing of mortar joints in masonry (stone or brick). In exposed masonry, joints are considered to be the weakest and most vulnerable spots from which rain water or dampness can enter. Pointing means implementing the joints to a depth of 10 to 20mm and filling it with better quality mortar in desired shape. Mortar required for pointing work: 1. Lime mortar of 1:2 ( 1 fat lime : 2 sand or surkhi ) 2. Cement mortar of 1:3 ( 1 cement : 3 sand) Above mortar mixes will give good results in pointing. Preparation of surface: All the joints in masonry are raked down to a depth of 20mm while the mortar is still soft. The joints and surface are cleaned and then thoroughly wetted. POINTING

12. Types of pointing: Flush pointing Recessed pointing Beaded Pointing Struck Pointing Flush pointing: In This type of pointing mortar is pressed hard in the raked joints and by finishing off flush with the edge of masonry units. The edges are neatly trimmed with trowel and straight edge. It does not give good appearance. But, flush pointing is more durable because of resisting the provision of space for dust, water etc., due to this reason, flush pointing is extensively used. Rubbed, keyed or grooved pointing Tuck Pointing V- pointing Weathered pointing POINTING

13. Recessed pointing: In case of recessed pointing mortar is pressing back by 5mm or more from the edges. During placing of mortar the face of the pointing is kept vertical, by a suitable tool. This type of pointing gives very good appearance. Beaded pointing: It is a special type of pointing which is formed by a steel or ironed with a concave edge. It gives good appearance, but it will damage easily when compared to other types. Struck pointing: This is a modification of flush pointing in which the face the pointing is kept inclined, with its upper edge pressed inside the face by 10mm. struck pointing drains water easily.

14. Rubbed, keyed or grooved pointing: This pointing is also a modification of flush pointing in which groove is formed at its mid height, by a pointing tool. It gives good appearance. Tuck pointing: In case of tuck pointing mortar is pressed in the racked joint first and finishing flush with the face. While the pressed mortar is green, groove or narrow channel is cut in the center of groove which is having 5mm width and 3mm depth. This groove is then filled with white cement putty, kept projecting beyond the face of the joint by 3 mm. if projection is done in mortar, it is called bastard pointing or half tuck pointing. V- Pointing: This pointing is formed by forming V-groove in the flush-finishing face. Weathered pointing: This pointing is made by making a projection in the form of V-shape .

15. Building mortars are mixtures used for the jointing of bricks, stones, blocks, etc. Mortar may be defined as a paste (capable of setting and hardening) obtained by adding water to a mixture of fine aggregates such as sand and binding material, e.g., clay, gypsum, lime or cement or their combinations. MORTAR Classification of Mortars : The governing factors in deciding a particular type of mortar for a specific structure depends upon the desired strength of masonry, resistance to penetration of rain water, immediate and long term appearance, hardening temperature, expected working conditions of the building and cost. For most practical purposes a building mortar will fall in one of the following classes: Cement Mortars : are prepared from Portland cement or its varieties, sand and water. Lime Mortars : are mixture of air hardening lime or hydraulic lime, sand and water. Gypsum Mortars : are prepared from gypsums or anhydride binding materials. Mud Mortars : are prepared from clay nodules and are used in construction of houses for poor and temporary construction works. Composite Mortars : may be surkhi-mortar (surkhi, lime and water), lime-surkhi-sand mortar, cement-lime mortar and cement-clay mortar.

16. Characteristics of Mortar 1. Strength : The strength of masonry depends upon both the mortar and the building unit (brick, stone or block). A very strong mortar with weak building units will be of little use. It is also important to consider whether full strength is required within a short time. In cold weather, when the strength of lime or cement mixes develops slowly, this is likely to affect the choice of mix. Strong cement mortars are most likely to lead to shrinkage cracks, and should, therefore be avoided except where high strength is an essential requirement. 2. Resistance to penetration of rain: The mortar for plastering should protect the masonry joints and units by forming an impermeable sheet. A satisfactory bond between the building units, mortar and plaster should be ensured. 3. Mobility and Place ability: The term mobility is used to indicate the consistency of mortar. The placeability is the ease with which the mortar mix can be applied with a minimum cost in a thin and uniform layer on the surface. Depending on its composition a mortar may have a consistency ranging from stiff to fluid. 4. Water Retention: It is characterized by the ability of mortar not to stratify during transportation and to retain adequate humidity in a thin layer spread over a porous bed.

17. Properties of a good mortar: 1) It should be cheap. 2) It should be durable. 3) It should set quickly. 4) It should be easily workable. 5) It should be capable of developing good adhesion with the building units such as bricks, stones etc. 6) It should be capable of resisting penetration of rain water. Uses of mortar: 1) To form joints of pipes. 2) To bind the building units such as bricks, stones, etc. into a solid mass. 3) To carry out pointing and plaster work on exposed surface of masonry. 4) To improve the general appearance of structure. 5) To hide the open joints of brickwork and stonework. 6) To fill up the cracks detected in the structure during maintenance process. MORTAR

18. Until the invention of Portland cement, lime was used as the chief cementing material in the building construction both for mortar and plasters. Most of the ancient palaces, forts, temples, monuments, etc., have been built with lime. The raw material for the manufacture of lime (CaO) is calcium carbonate which is obtained by the calcination of lime stone. Lime Lime is obtained by burning limestone at a temperature of about 800°C.

19. Types of Lime

20. 1. Lime possesses good plasticity and is easy to work with. 2. It stiffens easily and is resistant to moisture. 3. The excellent cementitious properties make it most suitable for masonry work. 4. The shrinkage on drying is small because of its high water retentivity. Characteristics of lime In construction slaked lime is mainly used to make mortar for laying masonry and plastering. When so used quick lime should be completely hydrated by slaking from 3 to 14 days, depending upon the kind of lime, temperature, and slaking conditions. Hydrated lime, although immediately usable, is usually improved by soaking overnight or longer. Hydrated lime is often added to Portland cement mortar in proportions varying from 5 to 85 per cent of the weight of the cement to increase plasticity and workability. Most of the historical buildings had been plastered in lime. Lime punning—about 3 mm thick shell lime layer to improve the plastered surfaces and to give a shining appearance—is used very commonly now a days in the new structures. Some of the other uses of lime are manufacture of lime bricks, artificial stones, paints, glass; as stabilizer for soils and as a flux in metallurgical processes. Uses of lime

21. According to the percentage of calcium oxide and clayey impurities in it, lime can be classified as lean, hydraulic and pure lime. Since magnesium oxide slakes slowly, an increase in its percentage decreases rate of hydration and so is with clayey impurities as well. 1. Lean or Poor : It consists of CaO + MgO 80 to 85% with MgO less than 5% and clayey impurities of about more than 7 per cent in the form of silica, alumina and iron oxide. It sets on absorbing CO2 from atmosphere. Characteristics: 1. Slaking requires more time and so it hydrates slowly. Its expansion is less than that of fat lime. 2. It makes thin paste with water. 3. Setting and hardening is very slow. 4. The colour varies from yellow to grey. Uses : It gives poor and inferior mortar and is recommended for less important structure. Classification of Lime

22. 2. Hydraulic Lime : It is a product obtained by moderate burning (900°-1100°C) of raw limestone which contains small proportions of clay (silica and alumina) 5-30 per cent and iron oxide in chemical combination with the calcium oxide content ( CaO + MgO 70-80% with MgO less than 5%). 3. Pure, Rich or Fat Lim : It is soft lime ( CaO + MgO more than 85% with MgO less than 4%) obtained by the calcination of nearly pure limestone, marble, white chalk, oolitic limestone and calcareous tufa. Fat lime is nearly pure calcium oxide and when it is hydrated with the required amount of water the solid lumps fall to a soft fine powder of Ca (OH)2 and the high heat of hydration produces a cloud of steam. It sets on absorbing CO2, from atmosphere. Characteristics: 1. Slaking is vigorous and the volume becomes 2-3 times. 2. It sets slowly in contact with air, and hence is not suitable for thick walls or in wet climate. 3. If kept under water a fat lime paste does not lose its high plasticity and consequently does not set and hard. Uses: Fat lime finds extensive use in making mortar, matrix for concrete, base for distemper and in white wash, manufacturing of cement, and metallurgical industry.