Finishing works

Cladding is a non-load-bearing covering or skin of material (stone, tile, brick, timber, metal, glass, GRC, etc.) fixed to the face of a wall or frame, either inside or outside, to protect it and to improve its appearance.

Types of cladding and their use

  Stone cladding         Tile hanging
  wall |[stone]cramp     wall |batten
  wall |[stone]          wall |=tile=
  wall | mortar          wall |=tile=

Functions (purposes)

• Weather protection: keeps out rain, wind and sun.
• Appearance: gives a pleasant, durable finish.
• Thermal and sound insulation when combined with insulating backing.
• Fire resistance and protection of the structure.
• Protection of walls from abrasion, dampness and chemical attack.
• Low maintenance and longer life of the wall.

A suspended (false) ceiling is a secondary ceiling hung below the main structural slab or roof by hangers, leaving a space between them.

Types

• Gypsum board (plasterboard) on a metal frame, with joints taped and painted.
• Mineral fibre / acoustic tile in a lay-in grid.
• Metal panels (aluminium, galvanised steel) such as strip, tile or grid.
• Timber and plywood panels.
• PVC and fibre cement boards for low cost.
• Glass or plastic panels for decoration.

Functions

• Hides services (ducts, pipes, wiring, AC).
• Lowers ceiling height for thermal, acoustic or lighting effect.
• Acoustic control and thermal insulation.
• Fire resistance and improved appearance.
• Allows easy access to services.

Fixing (construction)

1. Marking: the ceiling level is marked around the wall using a laser or water level.
2. Perimeter channel: wall angle (L-channel) is fixed to the wall at the marked level with screws.
3. Hangers: GI wire rods or threaded rods (about 6 mm) are fixed to the slab with anchor fasteners at 1.0-1.2 m spacing.
4. Main runners (T-grid): main channels are hung at 1.2 m c/c and levelled.
5. Cross runners: secondary runners are clipped between the main runners at 600 mm (or 400 mm) c/c.
6. Boards or tiles: panels are laid in the grid or screwed to channels; for gypsum boards, joints are taped, filled and painted.
7. Finishing: painting, fitting light fixtures, diffusers, and cleaning.

   RCC slab ==========================
        |hanger        |hanger
        |              |
   -----+-main runner---+--------
        cross runner  |
   [tile][tile][tile][tile]
   wall angle at perimeter

Pointing is the finishing of joints in exposed brick or stone masonry by raking out the mortar to a depth of about 12-20 mm and filling them with a better mortar (usually cement-sand 1:3 or lime mortar) to protect the joints from weather and improve appearance.

Types of pointing

1. Flush pointing: mortar is filled and pressed level with the wall face. Simple, strong, but does not look striking.
2. Recessed pointing: the mortar is pressed back 5-10 mm from the face. Gives shadow; not suitable in heavy rain areas.
3. Rubbed (keyed) pointing: joint is rubbed with a pointed tool to give a concave surface; good durability.
4. Weathered (struck) pointing: the upper part of the joint is pressed back so water flows off easily. Used widely in exposed walls.
5. Tuck pointing: a groove is cut in the flush mortar and filled with white cement putty in a thin raised bead. Gives a fine line but high cost and skill.
6. V-shaped pointing: a "V" groove is made in the joint.
7. Beaded pointing: a bead is formed with a round tool.
8. Raised (projecting) pointing: joint stands out from the face. Poor durability.

  flush    recessed   weathered   keyed(rubbed)  V-joint
  |  |     |  |_|     |  /|        |  (_)       |  \/
  ----     ----       ----         ----          ----

Procedure (method) of pointing

1. Rake out the joints to a depth of 12-20 mm with a raking tool and brush out dust.
2. Wet the surface thoroughly.
3. Prepare the mortar (cement-sand 1:3 for brick, or lime-surkhi), neither too wet nor too dry.
4. Fill the joints with a pointing trowel and press it firmly.
5. Finish to the type of pointing with a suitable tool.
6. Trim excess mortar and clean the face.
7. Cure for at least 7 days, and wet daily.

Plastering is the process of covering rough walls and ceilings with a coat of cement-sand mortar to give a smooth, even, durable and good-looking surface that also protects against weather.

Types of cement-sand plaster

• Single coat plaster: 12-15 mm in one coat, for ordinary work.
• Two-coat plaster: 12 mm base coat and 6-8 mm finishing coat; most common.
• Three-coat plaster: 9-12 mm scratch coat, 6-8 mm floating coat, 2-3 mm finishing coat; best quality.
• Sand-faced, rough cast, pebble dash and stucco are decorative finishes.

Proportion

Cement-sand 1:4 for external walls (1:6 for internal walls) and 1:3 for finishing coats and ceilings.

Procedure

1. Preparation: rake out the joints 10-12 mm deep; clean the surface of dust and oil; wet the wall.
2. Fixing guides: vertical lines are marked with plumb bob; patches of plaster or screed strips (gauges) are placed at 2 m c/c in level with the final plaster face.
3. Mortar preparation: cement and sand are mixed dry, and then water is added to get a workable mix.
4. Applying the first coat (scratch coat): mortar is thrown with a trowel and pressed firmly; surface is levelled with a flat wooden rule and scratched to form a key.
5. Second coat: after the first has set (1 day), apply 6-8 mm of floating coat, levelled.
6. Finishing coat: rubbed with a wooden float or trowel for a smooth or textured finish.
7. Curing: keep wet for at least 7 days.

   wall|scratch coat|floating|finish
       | 12 mm      | 8 mm   | 3 mm

A suspended (false) ceiling is used in buildings for the following reasons.

• Conceals services: wires, pipes, ducts and AC equipment are hidden above it.
• Reduces room height where the structural ceiling is too high, so heating and cooling cost less.
• Improves acoustics: sound-absorbing panels reduce noise and echo.
• Thermal insulation: the air space and insulation reduce heat gain and loss.
• Better lighting: recessed lights and a smooth reflective surface.
• Fire protection: fire-rated boards protect the structure and give time to escape.
• Appearance: hides rough soffits, beams and defects, and allows decorative designs.
• Easy access to services above through removable panels.

Why pointing is necessary

• Protects the mortar joints from rain, weather and attack.
• Prevents water seepage into the wall.
• Improves the appearance of exposed brick or stone masonry.
• Increases the life of the wall without needing plaster.
• Cheaper than plastering.

Defects in plastering

• Cracks: from shrinkage, poor curing, thermal movement, or poor mortar mix.
• Blistering: swelling from slaking of lime particles.
• Peeling/flaking: poor adhesion due to dirty, dry or smooth surface.
• Efflorescence: white salts coming to the surface from dampness.
• Hollowness (drummy plaster): poor bonding with background.
• Grinning: joint lines of the masonry show through the plaster.
• Rust stains: from metal or iron in the wall.
• Uneven surface, and popping (pits caused by lime or pebbles).

Constituents of oil paint

Internal partitions

A partition is a thin wall that divides a floor space into rooms. It is non-load-bearing, only carries its own weight, and is built of brick, block, timber, glass, metal or similar light material.

Requirements of a good partition

• Light in weight, and thin, so it takes less floor space.
• Stable and strong against its own weight and normal impact.
• Fire resistant and good sound insulation.
• Termite, damp and rot proof.
• Easy and quick to construct, and cheap.
• Smooth, good appearance and takes plaster or paint.
• Allows pipes and wiring to be run.

Classification

By material:

• Brick partitions: plain, reinforced or brick nogging; 10 cm thick.
• Clay or concrete block partitions: hollow blocks.
• Glass partitions: glass panes in wooden or aluminium frames.
• Timber partitions: studs and plywood or boards, framed or plain.
• Metal partitions: sheets of aluminium or steel on a frame.
• Plaster slab / gypsum board partitions.
• Asbestos / fibre cement and straw board partitions.
• RCC partitions.

By loading system:

• Load-bearing partitions: carry load of the floor above (act as walls).
• Non-load-bearing partitions: carry only own weight.

 Timber stud partition
  top plate ==============
   | stud  | stud  | stud |
   |-nogging-------------|
  sole plate =============

A partition wall is a thin vertical wall that divides the interior of a building into rooms or areas. It is non-load-bearing in most cases.

Types

• Brick partitions: plain, reinforced, nogged.
• Clay or concrete block partitions.
• Glass partitions (fixed or sliding).
• Timber partitions: plywood, framed.
• Metal partitions: aluminium or steel sheet.
• Gypsum board and plaster slab partitions.
• Fibre cement / asbestos-free sheet partitions.
• RCC and precast panels.

Functions

• Divides space for rooms.
• Gives privacy and security.
• Provides sound insulation and fire resistance.
• Carries doors, windows and fixtures.
• Hides services such as pipes and wires.
• Can be shifted (movable partitions) to change layout.
• Thin, so more usable floor space.

Painting on metal surfaces (iron and steel)

1. Cleaning: remove rust, scale, oil and grease by scraping, wire brushing, sand paper, or by solvent wash/sand blasting.
2. Priming coat: apply a red oxide or zinc chromate primer by brush to prevent rust, in one or two coats. Allow 24 hours to dry.
3. Stopping: fill dents and holes with putty and sand it smooth.
4. Second coat (undercoat): apply an undercoat of enamel or oil paint. Let it dry and rub down lightly.
5. Finishing coat: apply one or two coats of enamel or synthetic paint of the colour, with 24 hours between coats.

Precautions: work in dry weather, do not paint a wet surface, and use the same make of primer and finish.

Painting on masonry (plastered) surfaces

1. Surface preparation: the plaster must be at least 3-4 weeks old and dry. Remove dust, grease and efflorescence with a wire brush; fill cracks with putty.
2. Priming: apply an alkali-resistant primer or cement primer.
3. Putty: apply wall putty in 2 coats, rubbing with sand paper after each.
4. Painting: apply two coats of emulsion, distemper or cement paint with brush or roller, with a drying gap of 4-6 hours.
5. Cement paint: the surface is wetted before and cured after the application.

Painting is the application of a liquid coating to a surface to protect it from weather, dampness, rot and corrosion, and to give a good appearance and colour.

New woodwork

1. Preparation: the surface is rubbed with sand paper; knots are covered with a knotting solution (shellac) to stop resin bleeding.
2. Priming: a coat of primer (wood primer, red lead and linseed oil) is applied, and allowed to dry for 24 hours.
3. Stopping: nail holes and cracks are filled with putty (whiting and linseed oil), and the surface is rubbed down.
4. Undercoat: one or two coats of paint of lighter shade are applied with a gap of 24 hours, each sandpapered.
5. Finishing coat: one or two coats of the final colour (oil paint or enamel) are applied.

Old woodwork

1. Cleaning: old loose paint is removed by scraping, wire brushing or a paint remover, and the surface is washed with a mild soap or sugar solution; then dried.
2. Rubbing down with sandpaper.
3. Patch priming of bare areas, stopping and filling of holes, then sandpapering.
4. Undercoat and finishing coats as for new woodwork. If the old paint is sound, a single coat or two coats are applied.

Cement surfaces

The plaster must dry for 3-4 weeks; alkali-resistant primer is applied, then putty, then two coats of emulsion or cement paint.

Cladding is a non-load-bearing covering or skin of material (stone, tile, brick, timber, metal, glass, GRC, etc.) fixed to the face of a wall or frame, either inside or outside, to protect it and to improve its appearance.

Cladding fixed to a structural backing

Here the cladding is fixed directly to a structural wall or frame (the backing), which carries its load. The backing may be a brick, block, concrete or steel wall.

Methods of fixing:

• Adhesion (bonded): thin tiles or slabs bonded to the backing with mortar or adhesive, over a rough plaster. Used for tiles and thin stone.
• Mechanical fixing: stone slabs are fixed by metal cramps, dowels, or anchors to the backing, leaving a cavity of 25-50 mm filled with grout or kept open.
• Hung on battens or rails: timber or metal battens are fixed to the backing, and boards or tiles hung from them.

  Stone slab fixed to backing
  backing wall | 25-50 mm gap | slab
  wall |==cramp==|[ stone slab ]
  wall |  dowel  |[ stone slab ]

Merits: good support, a secure fix, lower cost, less space. Critical points / demerits:

• Differential movement between cladding and backing (due to temperature and moisture) can crack the cladding or cause failure.
• Movement joints are needed every 3-6 m.
• Moisture trapped behind the cladding can cause efflorescence and corrosion of fixings.
• Fixings should be of stainless steel or brass.
• Heavy slabs need strong anchors and the backing must be sound and dry.

Building finishes are the final surface treatments applied to floors, walls, ceilings and roofs, such as plaster, paint, cladding and flooring, to protect the structure and improve its appearance.

 TILE HANGING (section)       STONE CLADDING (section)
  wall | batten                wall | 25-50 mm gap
  wall |=tile (overlap)        wall |==cramp==[stone slab]
  wall |=tile                  wall |   dowel [stone slab]
  wall |=tile                  wall |   mortar grout

Brick cladding is a covering of thin bricks or brick slips fixed to a structural wall or RCC frame for appearance and weather protection. It is non-load-bearing.

Features

• Uses special facing bricks, brick tiles (12-25 mm thick slips) or full-size bricks as an outer leaf.
• Bricks are fixed with cement mortar over a rough-plastered backing, or by adhesive, or tied to the frame with stainless steel ties and a cavity.
• Joints are pointed with cement mortar (flush, struck or recessed).
• Movement joints are needed at storey heights and every 6-10 m.

Advantages

• Attractive, natural look and wide variety of colours and textures.
• Durable and fire-resistant, with low maintenance.
• Weather protection and thermal insulation.
• No need for paint or plaster.

Disadvantages

• Higher cost than plaster.
• Needs a skilled mason and good fixing.
• Efflorescence and water seepage if poorly detailed.

   backing wall | cavity | brick leaf
   RCC/brick    | 25 mm  |[brick]
   wall tie  ---+--------+-- stainless steel

The functions of painting work are:

• Protection: protects surfaces from weather, moisture, rust, rot, insects and chemical attack.
• Decoration: gives colour, texture and a pleasant appearance.
• Hygiene: gives smooth surfaces which are easy to clean, preventing dirt and germs.
• Preservation: increases the life of wood, steel and plaster.
• Light reflection: light colours improve room brightness.
• Identification and safety: colour coding of pipes and signs.
• Other uses: fire resistance, heat reflection, damp resistance.

Cracks in plastering arise from:

• Shrinkage of rich cement mortar (too much cement or water) or poor curing.
• Poor quality sand (too fine or with clay and silt).
• Poor bond to the background, dry or dusty wall, or smooth surface without a key.
• Movement of the structure: settlement, thermal and moisture movement of the wall or frame.
• Different materials meeting at one surface (brick and RCC) without mesh or a joint.
• Excess thickness applied in a single coat.
• Premature drying from sun and wind.
• Vibration, overloading, or structural cracks passing through the plaster.

Plastering

Plastering is the covering of rough walls, ceilings and columns with a coat of mortar (cement-sand 1:4 to 1:6, or lime) to give a smooth, even, protective surface. It hides defects, protects the masonry from weather, and takes paint. A two-coat plaster has a 12 mm base coat and a 6-8 mm finishing coat. The wall is cleaned, joints raked, and the surface wetted before applying. Curing is done for 7 days.

Pointing

Pointing is the finishing of mortar joints of exposed brick or stone masonry by raking out the joint 12-20 mm and refilling with richer mortar (cement-sand 1:3) in a chosen shape: flush, recessed, struck, keyed, V-shaped, beaded, or tuck. It protects joints from rain and improves appearance, without covering the whole wall.

Difference: plastering covers the whole surface; pointing treats only the joints.

Partitions are classified by the material used, and by whether they carry load.

With respect to materials

• Brick partitions: plain brick (half-brick), reinforced brick, and brick nogging (bricks in timber frame).
• Clay or concrete block partitions: hollow or solid blocks, light and quick.
• Glass partitions: glass panes in timber or aluminium frames; fixed, sliding or folding.
• Timber partitions: stud and plywood or boards, plain, framed or glazed.
• Metal partitions: aluminium or GI sheets on a frame.
• Gypsum board / plaster slab partitions: boards fixed on a light metal or timber frame.
• Asbestos-free fibre cement sheets, straw board.
• RCC and precast panels.

With respect to loading

• Load-bearing partitions: support the floor or roof above in addition to dividing space; usually brick, block or RCC.
• Non-load-bearing partitions: carry only their own weight; usually light materials like timber, glass, gypsum board.

 Brick partition        Stud partition
 |brick|   |            top plate
 |brick|   |            | stud | stud |
 half brick wall        sole plate

Emulsion paint is a water-based paint in which fine particles of a binder (acrylic, PVA or vinyl) are dispersed in water with pigments. It dries quickly by evaporation of water, has little smell, can be washed, and is used for walls and ceilings.

Stepwise procedure for painting new woodwork

1. Clean the surface and sandpaper it smooth.
2. Seal knots and resinous patches with knotting (shellac) solution.
3. Apply a coat of wood primer; leave 24 hours to dry.
4. Fill holes and cracks with putty (whiting and linseed oil), and rub down.
5. Apply the first undercoat and let it dry.
6. Sand lightly and apply a second undercoat if needed.
7. Apply one or two finishing coats of enamel or oil paint, with at least 24 hours between coats.
8. Clean the brushes and protect the surface from dust until dry.

Oil paint is a mixture of a pigment suspended in a drying oil, thinned with a solvent. The ingredients are:

The mixture is ground to a fine paste. Paint thus dries by evaporation of thinner and oxidation of the oil to form a tough, glossy film.

Paints

Paint is a liquid mixture of pigment in a vehicle which, when applied on a surface and dried, forms a thin protective, decorative film. It protects against weather, moisture, rust and rot, and improves appearance.

Ingredients of oil paint

Characteristics of a good paint

• Easily applied, spreads evenly with a brush.
• Good covering power (opacity) with fewer coats.
• Dries in a reasonable time into a hard, smooth, glossy film.
• Durable, resists weather, heat and abrasion.
• Does not crack, peel, blister or fade.
• Washable, non-toxic and fire-retardant.
• Gives good colour and is economical.

Painting on new and old woodwork

New woodwork:

1. Rub the surface with sand paper; seal knots with knotting (shellac) solution.
2. Apply a priming coat (red lead with linseed oil); allow 24 hours.
3. Fill holes and cracks with putty; sand smooth.
4. Apply one or two undercoats, each sandpapered after drying.
5. Apply one or two finishing coats of the final colour.

Old woodwork:

1. Remove old peeling paint by scraping, a blow lamp or paint remover; wash and dry.
2. Rub down with sand paper and fill defects with putty.
3. Spot prime bare areas.
4. Apply undercoat then finishing coats as for new work.

Paint and varnish

• Paint: a mixture of pigment, vehicle and thinner that forms an opaque, coloured, protective film on a surface when dry.
• Varnish: a solution of resin (lac, copal, rosin) in a solvent (turpentine, spirit, or oil) which dries to a hard, glossy, transparent film. It protects and brings out the natural grain of woodwork. Types: oil varnish, spirit varnish, turpentine varnish, water varnish.

Constituents of oil paint

Painting procedures

1. New and old woodwork New woodwork:

1. Rub the surface with sand paper; seal knots with knotting (shellac) solution.
2. Apply a priming coat (red lead with linseed oil); allow 24 hours.
3. Fill holes and cracks with putty; sand smooth.
4. Apply one or two undercoats, each sandpapered after drying.
5. Apply one or two finishing coats of the final colour.

Old woodwork:

1. Remove old peeling paint by scraping, a blow lamp or paint remover; wash and dry.
2. Rub down with sand paper and fill defects with putty.
3. Spot prime bare areas.
4. Apply undercoat then finishing coats as for new work.

2. Metal work Metal works: remove rust and scale with a wire brush or sand paper; apply red oxide or zinc chromate primer; apply an undercoat after 24 hours; finish with one or two coats of enamel or synthetic paint.

3. Cement surface Cement/plastered surfaces: the plaster must be dry (3-4 weeks old); remove dust and efflorescence; apply alkali-resistant primer; fill defects with wall putty; apply two or more coats of emulsion, distemper or cement paint (wetting the surface before cement paint and curing after).

Painting on masonry surfaces

1. Preparation: plaster must be at least 3-4 weeks old and fully dry. Remove dust, oil, loose particles and efflorescence with a wire brush and wash.
2. Repair: fill cracks and holes with cement mortar or putty and let them dry.
3. Primer: apply an alkali-resistant primer.
4. Putty: apply wall putty in two coats; rub down with sandpaper after each.
5. Painting: apply two coats of emulsion, distemper or cement paint with a brush or roller. The second coat is applied after 4-6 hours. For cement paint, wet the surface first, and cure the paint for 2 days.

Causes of cracks in buildings

Remedial measures