UNIT.V : FINISHINGS

Prepared by:K.SAHITYA,

Asst prof.

Civil engineering dept.

BVC college,odalarevu

Syllabus:Damp Proofing and water proofing materials and uses – PlasteringPointing, white washing and distempering –Paints: Constituents of a paint – Types of paints – Painting of new/oldwood- Varnish.Form Works and Scaffoldings.

Damp proofing

Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Damp problems are one of the most frequent problems encountered in homes.

Dampness a common problem in buildings.

It refers to access and penetration of moisture content into buildings through its

walls, floors, roof etc.

It is important to take measures to prevent dampness.

Such measures is called damp proofing.

Water proofing is a treatment of the surface or structure in a building to prevent leakage.

Causes of damp proofing:

Moisture from ground:-The materials used for the foundation and floors absorb moisture from the soil and it rises up the surface of the building,

Splashing of rain:-When rain splashes on external walls dampness may enter the interior.

Exposed top wall:-dampness enters from the top if the tops of parapet walls are not given sufficient damp proofing course.

Condensation: dampness is caused due to condensation of atmospheric moisture, deposited on walls and ceilings.

Construction defects:-

Improper planning, lack of proper slope in roof, defective pipe fittings, improperly sealed construction joints

are constructive defects.

EFFECTS OF DAMPNESS

Ugly patches on walls and ceilings.

Plaster softens and crumbles.

Materials used for wall decorations are damaged.

Stones ,bricks and tiles disintegrate due to efflorescence.

Floor finish may be damaged

Woodworks decays due to dry rot.

Metal components of building corrodes.

Electrical fittings are damaged,

Dampness leads to

breeding of mosquitoes, growth of termites and germs carrying

diseases such as tuberculosis, it also aggravates asthma.

Materials for damp proofing

Requirements of ideal materials for damp proofing:-

They should be :-

impervious.

Durable

Capable of bearing the load

Dimensionally stable

Flexible

Free from sulphates, chlorides and nitrates.

Inexpensive

various materials used for damp proofing:

Hot bitumen :-hot bitumen,3mm thick may be applied on bedding of mortar or concrete.

Mastic asphalt:-semi rigid material obtained by heating asphalt with sand and mineral fillers. It is laid on mortar or concrete bed.

Bituminous felt:-flexible material available in rolls. It is laid on flat mortar finished surfaces.

Metal sheets:-sheets of lead, copper and aluminum may be used membranes in damp proofing. Lead is the most ideally suited material.

Combination of sheets and felts:-economical and drable damp proofing sheet is obtained by sandwiching a lead sheet and bituminous felt.

plastic sheets:-a relatively cheap method

of damp proofing is by laying 0.5-1.0mm thick plastic sheets made of black polythene. This is not a permanent method.

Bricks:-quality bricks absorbing water less than 4.5% of their weight may be used for damp proofing. These bricks are laid in 2-4 courses in cement mortar.

Cement concrete course:-a cement concrete course of proportion 1:2:4 and thickness 75-150mm is laid on masonry at plinth level.

Principles of damp proofing

mortar bed prepared to receive damp-proof course should be leveled.

The horizontal damp proofing course should cover the full width of wall excluding rendering.

If sheets or mastic asphalt are used, the gap should not be less than 100mm at any point.

At joints and corners. Damp proof course should be continuous.

Damp proofing course should not be kept exposed on the wall surface.

At vertical and horizontal junctions, damp proof courses should be continuous and a cement mortar fillet of about 75mm should cover joints.

METHODS OF DAMP PROOFING:-

Different types of treatments are used for preventing dampness in diff parts of the building:-

Treatment for Foundations:-

this is method of protecting foundations of outer walls. An air drain is constructed parallel to the wall.

The drain is covered with RCC slab, and gratings are provided at regular intervals, horizontal and vertical damp proof courses are also provided.

Treatment for floors:-

if there is no damp soil, a layer of coarse sand,75-100mm thick is provided over entire area under the flooring. Then 1:4:8 concrete of 100mm thickness is laid. This layer serves as DPC. the usual flooring is provided over this, If soil is wet, a membrane DPC is provided over the floor area, over which a layer of flat bricks is laid. The usual flooring is then provided.

Treatment for walls:

the plinth level should preferably be 450mm above ground level.DPC should be provided over a concrete bed of thickness 100-200mm.the top of the parapet should be provided with capping over the DPC. the wall also needs DPC at the edge of the roof slab.

Providing foundation drains and DPC:-

to release hydrostatic pressure,trenches are made all around the building and filled with gravels etc. such trenches may also be required in buildings if the water table is at a higher level.

The trenches lead the water to a catch drain. Horizontal and vertical DPCs are provided in the walls and foundation concrete.

Providing RCC raft and wall slab:-

if the water pressure is high, providing a drainage system will not solve the problem effectively. In such cases the floor slab and wall may be prepared right through the RCC structure and DPC is applied on it.

Asphalt tanking:-

It is also known as membrane waterproofing. Construction of horizontal layers :a leveled course of mass concrete is laid for the flooring area ,over which a 30 mm thick DPC in form of asphaltic layer is provided a protective layer of cement screed, concrete or a layer of brick work is laid over the asphaltic layer, after which the flooring is prepared.

construction of vertical face:-

A vertical DPC is provided on the external face of the wall. The DPC consist of an asphalt layer of about 20mm built in three coats. This is then protected with a wall of ½ brick thickness.

Waterproofing of flat roofs:-

Lime concrete terracing :-

The RCC roof is cleaned thoroughly and a bitumen primer is applied ,3 coats of hot blown asphalt is then applied over which a specially prepared lime concrete bed of 100mmthickness is provided. The surface of bedding is covered with flat tiles. a convex corner joint is made at the junction with the parapet wall.

Membrane water proofing:-

water proofing membrane may be prepared with mastic asphalt or plastic sheet. It is provided in a number of layers from 2-7.in this method a layer of hot mastic asphalt is applied on the clean roof surface. This is covered by jute cloth and another layer of mastic asphalt is laid.

In case of plastic membranes, hot coating is applied with blown bitumen between each layer. The top is usually finished with a course of flat tiles.

At the junction is properly sealed with the parapet. The membrane should extend up to parapet or lead sheets should be inserted.

Using waterproofing compounds:-

Water proofing compounds may be grouped to 2:-

Waterproofing admixtures:-these admixtures are in powder or liquid form. About 2% of powders are mixed while making cement mortar. when the finishing coat of mortar is provided, these compounds seal the pores in the slab and make them watertight.

Waterproofing membrane system:-these materials are available in the form of paints, they may epoxy or elastomeric and may be applied to roof slabs with rollers ,brush or spray. a minimum of 2 coats are applied to get desired waterproofing.

Sloped RCC roofs are provided with tiles for purpose of weather proofing. It is preferable to use flat tiles fixed to roof.,If Mangalore tiles are used care should be taken. continuous motor bands should not be provided as reapers because in case rainwater

entering through broken tiles stagnates on the mortar bands, leakage will occur. Hence mortar bands supporting Mangalore tiles should be discontinuous. before laying the tiles, the possible leakage points should be checked and identified.

Plastering

Plastering is the process of covering rough walls and uneven surfaces in the construction of houses and other structures with a plastic material, called plaster or mortar. Objective of plastering •To provide an even, smooth, regular, clean and durable finished surface with improved appearance.

•To preserve and protect the surface.

•To cover up the use of inferior quality and porous materials of the masonry work.

•To conceal defective workmanship

Requirement of the good plaster: •It should be hard and durable. •It should be possible to apply it during all weather conditions. •It should adhere to the background and should remain adhered during all climatic changes. •It should be cheap and economical. •It should offer good insulation against sound and high resistance against fire. •It should effectively check the entry or penetration of moisture from the surfaces.

Types of plasters:

•Lime plaster

Lime plaster is a mixture of calcium hydroxide and sand (or other inert fillers) in 1: 1 ratio.

Carbon dioxide in the atmosphere causes the plaster to set by transforming the calcium hydroxide into calcium carbonate (limestone).

In order to improve building properties of lime plaster , gugal (a kind of fragrant gum) @ 1.6 kg/m3 of mortar , is added when the mortar is being ground.

In order to improve adhesive and tensile properties of lime mortar, sometimes, small quantities of chopped hemp (i.e., vegetable fibres) @ 1kg/m3 are added to the lime mortar.

The lime mortar thus prepared is usually kept for 2 days before use. Cement plaster:

Cement and sand in required proportions ( 1:3 or 4) are first thoroughly mixed in dry conditions and then water is added to form a paste of required consistency.

Generally it is mixture sand, portland cement and water mixed in a suitable proportion.

This prepared mortar for plastering should be consumed within 30 minutes after the addition of water.

Mud plaster

Mud to be used in plastering should be made from earth free from grass roots, gravel, stone grit etc.

Mud plaster is generally applied in two coats. The first coat being 18mm thick while the thickness of the second coat is kept 6mm. The plaster is dashed against the wall and worked with a straight edge and float. The second coat is applied only when the first coat has set(not dry).

Water proof plaster of Mortar:

This mortar consists of 1 part of cement, 2 parts of sand and pulverised alum @ 12 kg/m3 of sand. To this dry mix , the soap water containing about 75 g of soft soap/L of water , is added to obtain the waterproof mortar.

Gypsum plaster (plaster of Paris)

Gypsum plaster, or plaster of Paris, is produced by heating gypsum to about 300 °F (150 °C).

2CaSO4·H2O + Heat → 2CaSO4·½H2O + H2O (released as steam) When the dry plaster powder is mixed with water, it re-forms into gypsum. The setting of

unmodified plaster starts about 10 minutes after mixing and is complete in about 45 minutes but not fully set for 72 hours

•Heat resistant plasters

It's purpose is to replace conventional gypsum plasters in cases where the temperature can get too high for gypsum plaster to stay on the wall.

Heat resistant plaster should be used in cases where the wall is likely to exceed temperatures of 50°C .

Heat resistant plaster is a building material used for coating walls and chimney

breasts.

Defects in plastering The following defects may arise in the plaster work:

Blistering of plastered surface: 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. Cracking: it is the formation of cracks in the plaster work due to the following reasons:

Structural defects in building

Movements in the background due to its thermal expansion or rapid drying

Movements in the plaster surface itself, either due to expansion or shrinkage.

Efflorescence: It is the whitish crystalline substance which appears on the surface due to presence of salts in plaster making materials. It affects the adhesion of paint with wall surface. Efflorescence can be removed to some extent by dry brushing and washing the surface repeatedly.

Flaking: It is the formation of very loose mass of plastered surface, due to poor bond between successive coats.

Peeling: It is the complete dislocation of some portion of plastered surface, resulting in the formation of a patch. This also results from imperfect bond.

Popping: It is the formation of conical hole in the plastered surface due to presence of some particles which expand on setting.

Method of plastering (general) The plaster may be applied in one or more coats, but the thickness of a single coat

should not exceed 12 mm. In the case of inferior or cheaper type of construction, the plaster may usually be one

coat. For ordinary type of construction, the plaster is usually applied in two coats, whereas for superior type of works it is applied in three coats.

The final setting coat should not be applied until the previous coat is almost dry. The previous surface should be scratched or roughened before applying the next coat

of plaster. In plastering, the plaster mix is either applied by throwing it with great force against

the walls or by pressing it on the surface. Pointing

•It is the art of finishing the mortar joints in exposed brick or stone masonry with suitable cement or lime mortar, in order to protect the joints from weather effects and also to improve the appearance of building structure.

•Often an entire wall, or even a whole structure, is pointed because defective points cannot easily be detected, and adjacent joints may also be in need of repair. The mortar is packed tightly in thin layers and tooled to a smooth, concave, finished surface. Functions of pointing:

Maintaining the joints of the structures.

Pointing being cheap can be adopted in places of low rainfall.

Where the natural beauty of materials, viz., stone blocks, bricks etc, is desired to be exhibited.

Gives resisting power to the bricks and stones used in construction towards weather conditions.

Method of pointing •All the mortar joints (on the masonry face required to be pointed) are raked out by a special pointing tool to a depth of 15 to 20 mm, so as to provide an adequate key for the fresh mortar used for pointing.

•All the loose mortar and dust are removed by brushes

•The joints and wall surface are washed with clean water, and then kept wet for few hours.

•The joints so prepared, are filled with suitable mortar with a small trowel. The mortar is well pressed into the joints to form a close contact with the old interior mortar joints. All excess mortar sticking to the sides is scraped away.

•The finished pointing work is kept wet for about 3 days when lime mortar is used for pointing

and for 10 days when cement mortar is used for pointing. TYPES OF POINTING :

FLUSH POINTINGThe mortar is pressed into the raked joints and finished off flush with the edges of the bricks orstones, so as to give a smooth appearance. The edges are then neatly trimmed with a trowel andstraight edge.

CUT/WEATHERED/STRUCK POINTING

The mortar is first pressed into the raked joints. While the mortar is still green, the top of the horizontal joints is neatly pressed back by 3-6 mm with the pointing tool. Thus the joint is finished sloping from top of the joint to its bottom.

V GROOVED POINTINGThis type of pointing is made similar to keyed or grooved pointing by suitably shaping the end of the steel rod to be used for forming the grooving.

KEYED/GROOVED POINTINGThe mortar is pressed into the raked joints and finished off flush with the face of the wall. a groove is formed by running the bent end of a small steel rod (6mm in diameter) straight along the centre line of the joints. The vertical joints are also finished in the same manner

TUCK POINTINGThe mortar is first pressed in the raked joints and there after it is finished flush with the face of the wall. The top and bottom edges of the joints are cut parallel so as to have a uniformly raised band about 6mm high and 10mm in width.

BEADED POINTINGThe mortar is pressed in the raked joints and finished off flush with the face of the wall. A steelrod having its end suitably shaped is run straight along the centre line of joints to form the beading.

PAINTING:

functions• Protect the surface of wood, metal and all structures from atmospheric influences.• Prevent decay in wood • Prevent corrosion in metal• Provides clean ,smooth and colored surface

Ingredients of paint Base- solid matter Bases-White lead, red lead, oxides of zinc, antimony white Liquid vehicle carries the solid matter Acts as binding material Vehicles- linseed oil, Tung oil, stand oil, nut oil Additives Pigments- coloring agent Thinning agents- reducing consistency of paint- turpentine oil Driers- property of quick drying- cobalt, lead, manganese Function- to absorb oxygen from the atmosphere and transfer it to

linseed oil for hardening. Inert filler/Adulterant- improving the durability ex:Barium sulphate

Characteristics of good paint • Good spreading power• Dry quickly• Durable, tough, resistant to wear on drying• Color should not fade or change• Should work smoothly and freely• Become dry within 9 hours• Not crack on drying• Smooth and pleasing appearance.Process of Painting a plastered surface• For newly plastered wall, there is considerable amount of moisture.• For applying paint wait for at least 3to 6 months.• Defects in plastered surfaces are to be removed.• Coats of alkali resistant primer paint should then be applied on the surface.• Usual paints:- cement paint, silicate paint, emulsion paint

CLASSIFICATION OF PAINTS

On the basis of their applications, paints can be classified asa) Exterior house paints Generally have constituents such as pigment (ZnO, TiO2, white lead etc.), extenders (talc, barytes, clay etc), vehicle (e.g. boiled linseed oil) and thinners (e.g. mineral spirit, naphtha etc.) Coloured pigments for light tint are also added in varying amount. b) Interior wall paints

It is prepared by mixing pigments (e.g. white and colored pigments), vehicle (e.g. varnish or bodied linseed oil) and resins (e.g. emulsified phenol formaldehyde resins and casein)c) Marine paints Also known as antifouling paint and can be prepared by mixing various ingredients such as pigments (ZnO and venetian red), resin (shellac), driers (manganese lineolate), vehicle (coal tar), diluents (pine oil), toxic components(cuprous oxide and mercuric oxide) and small amount of bees wax. d) Emulsion paints These paints are highly durable, impermeable to dirt, resistant to washing, rapidly drying, contain water as thinner and can be easily cleaned. It contain an emulsion of alkyds, phenol formaldehyde etc.(vehicle) in water pigments and extenders are also added to get other desirable properties. e) Chemical resistant paints Consist of baked oleo resinous varnishes, chlorinated rubber compositions, bituminous varnishes and phenolic dispersion as chemical resistant materials in paint formulations. f) Fire resistant paints These paints impart a protective action on the article being coated through easy fusion of the pigments and other paint ingredients giving off fume on heating, they do not support combustion. It consist of borax, zinc borate, ammonium phosphate synthetic resins etc as anti-fire chemicals. g) Luminous paints Consist of phosphorescent paint compositions such as pigment (sulfides of Ca, Cd and Zn dispersed in spirit varnish), vehicle (chlorinated rubber, styrol etc.) and sensitizer for activation in UV region. h) Latex paints These paints usually contain

Protein dispersion: Prepared by soyabean proteins or casein in aqueous ammonia solution for about an hour at room temperature

Pigments: ZnS,TiO2 etc dispersed in water Extenders: clay, talc, MgSiO3, BaSO4 etc. Preservatives: Penta chlorophenol Antifoaming agent: Pine oil Plasticizer: Tributylphosphate Latex: Prepared from a butadiene styrene copolymer in water

All these ingredients well stirred in water, screened, again stirred and packed.i) Aluminum paints Used as heat reflecting paints and consist of pigment (aluminum powder) and vehicle (spirit varnishes) and cellulose nitrate lacquers. j) Metal paints Applied on the metal surfaces or bodies for protection and decoration and are of two types

Painting on new wood work:• Moisture content of timber must be less than 15% of their dryweight

• Four coats of paints are required• Before Prime coat Wood work to be cleaned thoroughly Nail holes and cracks to be filled with putty Rub the surface with water proof abrasive paper.

Painting on old wood work:• Old paint should be completely removed• Removing old paint

– Equal parts of washing soda and quick lime- mixture is brought to a paste form by adding water

– It is applied on the surface and kept for one hour, then washed off with water• After, wood surface is painted as that for new wood work.

Distempering• Water paint• Prepared by mixing powdered chalk(white) and glue, boiled in water• Earthly pigments- umber, Indian red and lamb black –give color shade• Powder or paste form- mixed with hot water to form viscous fluid• Distemper is porous• Allow water vapor to escape• less durable.• Use- to give smooth outer surface in low cost

varnishes Varnish is a transparent, hard, protective finish or film that is primarily used

in wood finishing but also for other materials. Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent.

Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents.

Varnish has little or no color, is transparent, and has no added pigment, as opposed to paints or wood stains, which contain pigment and generally range from opaque to translucent.

Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish.

Components of classic varnishDrying oil

There are many different types of drying oils, including linseed oil, tung oil, and walnut oil. These contain high levels of polyunsaturated fatty acids.

Resin

Resins that are used in varnishes include amber, kauri gum, dammar, copal, rosin (pine resin), sandarac, balsam, elemi, mastic, and others. Shellac is also a resin. In the 1900s in Canada, resins from local trees were used to finish pianos[citation needed]. As a result, these now antique pianos are considered difficult to refinish. However, shellac can be used over the existing resins provided sufficient time is allowed for thin coats to cure. Thus the original finish can be returned to its original lustre while preserving the color and age-related crackle.

Solvent (traditionally turpentine)

Traditionally, natural (organic) turpentine was used as the thinner or solvent, but has been replaced by several mineral-based turpentine substitutes such as white spirit or "paint thinner", also known as "mineral spirit".

Types of varnishesResin

Most resin or "gum" varnishes consist of a natural, plant- or insect-derived substance dissolved in a solvent, called spirit varnish or solvent varnish. The solvent may be alcohol, turpentine, or petroleum-based. Some resins are soluble in both alcohol and turpentine. Generally, petroleum solvents, i.e. mineral spirits or paint thinner, can substitute for turpentine. The resins include amber, dammar, copal, rosin, sandarac, elemi, benzoin, mastic, balsam, shellac, and a multitude of lacquers.

Synthetic resins such as phenolic resin may be employed as a secondary component in certain varnishes and paints.

Shellac

Shellac is a very widely used single-component resin varnish that is alcohol-soluble. It is not used for outdoor surfaces or where it will come into repeated contact with water, such as around a sink or bathtub. The source of shellac resin is a brittle or flaky secretion of the female lac insect, Kerria lacca, found in the forests of Assam and Thailand and harvested from the bark of the trees where she deposits it to provide a sticky hold on the trunk. Shellac is the basis of French polish, which for centuries has been the preferred finish for fine furniture. Specified "dewaxed" shellac has been processed to remove the waxy substances from original shellac and can be used as a primer and sanding-sealer substrate for other finishes such as polyurethanes, alkyds, oils, and acrylics.

Alkyds

Modern commercially produced varnishes employ some form of alkyd for producing a protective film. Alkyds are chemically modified vegetable oils which operate well in a wide range of conditions and can be engineered to speed up the cure rate and thus harden faster. Better (and more expensive) exterior varnishes employ alkyds made from high performance oils and contain UV-absorbers; this improves gloss-retention and extends the lifetime of the finish. Various resins may also be combined with alkyds as part of the formula for typical "oil" varnishes that are commercially available.

Spar varnish

Spar varnish (also called marine varnish) was originally intended for use on ship or boat spars, to protect the timber from the effects of sea and weather. Spars bend under the load of their sails. The primary requirements were water resistance and also elasticity, so as to remain adhering as the spars flexed. Elasticity was a pre-condition for weatherproofing too, as a finish that cracked would then allow water through, even if the remaining film was impermeable. Appearance and gloss was of relatively low value. Modified tung oil and phenolic resins are often used.

Drying oils

By definition, drying oils, such as linseed and tung oil, are not true varnishes though often in modern terms they accomplish the same thing. Drying oils cure through an exothermic reactionbetween the polyunsaturated portion of the oil and oxygen from the air. Originally, the term "varnish" referred to finishes that were made entirely of resin dissolved in suitable solvents, either ethanol (alcohol) or turpentine. The advantage to finishes in previous centuries was that resin varnishes had a very rapid cure rate compared to oils;.

Polyurethane

Polyurethane varnishes are typically hard, abrasion-resistant, and durable coatings. They are popular for hardwood floors but are considered by some wood finishers to be difficult or unsuitable for finishing furniture or other detailed pieces. Polyurethanes are comparable in hardness to certain alkyds but generally form a tougher film. Compared to simple oil or shellac varnishes, polyurethane varnish forms a harder, decidedly tougher and more waterproof film.

Lacquer

The word lacquer refers to quick-drying, solvent-based varnishes or paints. Although their names may be similarly derived, lacquer is not the same as shellac and is not dissolved in alcohol. Lacquer is dissolved in lacquer thinner, which is a highly flammable solvent typically containing butyl acetate and xylene or toluene. Lacquer is typically sprayed on, within a spray booth that evacuates overspray and minimizes the risk of combustion.

Acrylic

Acrylic varnishes are typically water-borne varnishes with the lowest refractive index of all finishes[and high transparency. They resist yellowing. Acrylics have the advantage of water clean-up and lack of solvent fumes, but typically do not penetrate into wood as well as oils. They sometimes lack the brushability and self-leveling qualities of solvent-based varnishes. Generally they have good UV-resistance.

Qualities of ideal varnish

It should be dry quickly.

On drying it should form a hard, tough and durable film. It should have good weathering properties, resist abrasion and wear well. It should be able to retain its colour and shine. It should be uniform and pleasant looking on drying.

.Form Works and Scaffoldings.

Form Works

Form workI is an artificial support provided below and around the precast or cast insitue concrete work

Its is an artificial support provided below and around the precast or cast insitue concrete work.

Formwork is commonly made of

o Steel

o wood

Formwork construction & casting is of prime importance in concrete industry. It share a significant amount of concrete cost.

Qualities of a form work

It should be water tight

It should be strong

It can be reusable

Its contact surface should be uniform

It should be according to the size of member

Some important things about form work

Due to continuous use wooden planks & steel plates surfaces become uneven and require maintenance.

For wooden formwork use cardboard or plastic fiber board. Bolt hole places must also be repaired.

For steel formwork plates must be leveled by mallet and loose corners must be welded.

Types of form works

Formwork are mainly of two types

Steel formwork

Wooden formwork

Steel formwork is made of

steel sheets

Angle Iron

Tee Iron

Wooden formwork consists of

Props

Planks battens

Ledgers

Sheeting

Formwork detail for different structural members

In concrete construction formwork is commonly provided for the following structural members.

Foundations

Wall

Column

Slabs & beams

Stairs

Advantages of steel form work

It can be used for a no. of times. It is non absorbent. Smooth finish surface obtained. No shrinkage of formwork occurs. Easy to use. Its volume is less

Its strength is more.

Scaffolding

It’s a temporary structure to provide a platform at different levels of a building for workers and Materials.

Following are the types of scaffolds

1. Single Scaffolds

2. Double Scaffolds

3. Ladder Scaffolds

4. Cantilever Scaffolds

5. Suspended Scaffolds

6. Steel or Tubular Scaffolds

Single scaffolding

It consists of Standards (v posts)(10 cm) Putlogs (7.5 x 7.5) Ledgers ( Wooden boards Braces

Used for ordinary buildings

Double scaffolding

It consists of

Two rows of standards.

15 cm, 1.5 m

Shores are provided.

Used for superior works

Ladder scaffoldings

It consists of Brackets for Plate form.

Cantilever scaffolding

It consists of Cantilever Struts Standards Putlogs Plate forms

It is used above ground level

Suspended scaffoldings

It consists of Ropes Working platforms

Ropes can be raised Manually or mechanically Used for light construction and finishing works of multistory buildings

Steel or tube scaffoldings

It consists of

Steel tubes (1-1/2” – 2-1/2” diameter) Coupler or Clamps (to hold pipes in different positions) Prop nuts (to hold single pipes) Bolts, Nuts & washers Wedge & Clip