Flooring

Terrazzo is a floor finish of cement and marble chips (aggregate) laid over a concrete base, ground and polished to a smooth, hard, attractive surface.

Materials

• Cement (white or grey, with colour pigments), marble chips 6-12 mm, sand/marble powder.
• Brass or glass dividing strips (3 mm thick, 40 mm deep).
• Oxalic acid and wax for polishing.

Construction method

1. Base: a concrete sub-floor (1:2:4, about 100 mm) is laid and levelled. Its surface is kept rough and cleaned, then wetted.
2. Under layer: a 25-30 mm cement-sand mortar (1:4) bed is spread and levelled while the base is still green.
3. Dividing strips: brass/glass/aluminium strips are fixed in the bed, in panels about 1 m x 1 m, with their tops at the finish level. They stop cracking and form patterns.
4. Topping: a mix of cement and marble chips (1:2 or 1:1.5 by volume; chips 6-12 mm), 6-12 mm thick, is spread in the panels, levelled and well rolled or pressed so the chips show on the surface.
5. Curing: cured under wet sand or gunny for 7-10 days.
6. Grinding: the surface is ground by a machine with carborundum stones: first coarse (No. 60), then medium (No. 120) and fine (No. 320), with water.
7. Grouting: pin holes are filled with a neat cement paste of the same colour and ground again.
8. Polishing: finally polished with oxalic acid powder and wax or polish.

   Section
   ___ marble chip topping (6-12 mm)
   ~~~ cement mortar bed 1:4 (25 mm)
   ... PCC sub-floor 1:2:4 (100 mm)
   --- compacted brick soling / earth
   |brass strip| every ~1 m

Terrazzo is hard, durable, easy to clean, and is used in hospitals, schools and offices.

A suspended ground floor is a ground floor whose floor structure (joists and boarding, or an RCC slab) is raised above the ground with an air space beneath, instead of resting directly on the earth. It is also called a hollow floor.

Purpose

• To keep the floor dry in damp sites or areas with a high water table.
• To give ventilation under the floor and prevent dry rot of timber.
• To make a warm floor surface (timber) and to run services.

Construction (timber type)

• Low sleeper walls (honeycomb brickwork, 1/2 brick, with gaps for air) are built on a 100-150 mm concrete layer, at about 1.2-2 m spacing.
• A damp proof course is laid on top of the sleeper walls and a wall plate (75 x 50 mm) is fixed on it.
• Joists (100 x 50 mm at 300-400 mm c/c) rest on the wall plates.
• Floor boards (20-30 mm thick) are nailed to the joists.
• Air bricks/vents in the external walls ventilate the void beneath. The space under the joists is kept at least 150 mm from the oversite concrete to the underside of the joists.

  floor boards ===================
  joists       |_|_|_|_|_|_|_|_|_|
  wall plate  [=]      [=]      [=]
  DPC          -        -        -
  sleeper wall |        |        |
  oversite  ___|________|________|__
  concrete  (100 mm, on hardcore)
  air bricks at the external walls

A suspended floor may also be an RCC slab on beams, with a void below.

A solid ground floor rests directly on the filled ground, while a suspended ground floor is raised above the ground with a ventilated air space below.

  SOLID                    SUSPENDED
  finish  =========        boards  ==========
  screed  ~~~~~~~~~        joists  |_|_|_|_|_|
  PCC     .........        void      (air)
  DPM     ---------        sleeper [|]  [|]
  hardcore ooooooo         concrete .........
  earth   ///////////      earth   //////////

A solid ground floor is a floor laid directly on the ground, with its layers supported by well-compacted earth fill. It is the most common floor in ground-level rooms.

Layers (from the bottom up)

1. Natural/compacted earth: top soil removed, then filled in layers of 150 mm and rammed to a firm base.
2. Hardcore (brick soling or stone): 100-150 mm of broken brick/stone, well rammed, to cut capillary rise and give a firm bed.
3. Sand blinding: about 25-50 mm to fill voids and prevent the concrete from leaking.
4. Damp proof membrane (DPM): 1000-gauge polythene or bitumen layer (a 12 mm asphalt coat is also used) to stop ground moisture. It is joined to the DPC of the walls.
5. Concrete bed (PCC): 100-150 mm thick, 1:2:4 or 1:3:6, over the whole room.
6. Screed: 20-25 mm cement-sand (1:4) to level the surface.
7. Floor finish: cement punning, terrazzo, tiles, marble, etc.

     wall        skirting
   +-----+  ___________________ finish
   |     |  ~~~~~~~~~~~~~~~~~~~ screed 25
   | DPC |= ___________________ DPM
   |     |  ...................  PCC 100-150
   |     |  ooooooooooooooooooo  hardcore 150
   +-----+  ///////////////////  compacted earth

The plinth must be at least 450 mm above the ground level (usual practice 300-450 mm) so the floor stays above the surrounding earth and rain water. A solid floor is suitable for dry, firm sites.

Mosaic flooring is made of small pieces of marble, stone, glazed tiles or broken china set in cement mortar over a concrete base, and polished to give a decorative surface. Factory-made mosaic tiles (cement-marble chips tiles) are also used.

Construction (in-situ mosaic)

1. Base concrete: a concrete sub-floor (1:2:4, 100 mm) is laid, levelled and left rough. It is cleaned and wetted before the next layer.
2. Mortar bed: a 20-30 mm layer of cement-sand mortar (1:3) is spread and levelled.
3. Dividing strips: glass, brass or aluminium strips are fixed in the mortar to form panels, usually 1 m x 1 m.
4. Mosaic pieces: marble or china pieces of selected size and colour are pressed into a thin layer (about 3 mm) of neat cement grout or paste, in the pattern wanted.
5. Rolling and levelling: the surface is beaten and rolled for level and even setting.
6. Curing: kept wet for 7 days.
7. Grinding and polishing: ground by a machine with stones of increasing fineness, voids are filled with cement paste, and the floor is finally polished with oxalic acid and wax.

Mosaic tile laying

Precast tiles (25 x 25 or 30 x 30 cm) are bedded on a 20-25 mm cement mortar (1:4) over the concrete base, joints are kept thin and filled with cement slurry, then the floor is cured and polished.

   mosaic pieces + cement paste ~~~~
   mortar bed 1:3 (20-30 mm)    ....
   PCC 1:2:4 (100 mm)           ====
   brass/glass strip in each 1 m panel

Marble flooring uses polished marble slabs (usually 18-25 mm thick) laid over a mortar bed. It gives a smooth, durable, attractive, easy-to-clean surface, used in halls, temples, offices and houses.

Materials

Marble slabs of uniform colour and thickness (e.g. 300 x 300 or 600 x 600 mm), cement, sand, white cement for joints, and polishing wax.

Construction method

1. Base: clean the concrete sub-floor, remove dust, and wet it.
2. Marking: set levels and lines with a string and level at the floor edges.
3. Mortar bed: spread a 20-30 mm cement-sand mortar (1:4), stiff (just damp) and levelled to the correct slope.
4. Neat cement slurry: spread over the bed so that the slab bonds well.
5. Laying slabs: soaked slabs are placed on the bed starting from a corner or the centre, tapped with a wooden mallet and checked with a straight edge and spirit level. Joints are kept thin (1-2 mm) and straight.
6. Joint filling: after 2-3 days the joints are cleaned and grouted with white or coloured cement paste.
7. Curing: kept wet for 7 days.
8. Grinding and polishing: the floor is ground with a machine with carborundum stones, then polished with oxalic acid and wax.

   marble slab 20 mm      =========
   slurry                 ~~~~~~~~~
   mortar 1:4 (25 mm)     .........
   PCC base               ---------

Precautions: use marble of good quality; keep the bed well compacted; avoid hollow spots and lippage between slabs; do not walk on the floor until it has set (about 3 days).

Flooring is the finished surface of a floor, laid over the structural base to give a hard, durable, level and good-looking surface. The common types are listed below.

Granite flooring uses polished slabs of natural granite (a hard igneous rock), usually 18-20 mm thick, laid on a mortar bed.

Construction process

1. Clean and wet the base concrete; set levels and lines.
2. Spread a 20-30 mm bed of cement-sand mortar (1:4), stiff and level, and a thin coat of neat cement slurry on top.
3. Place granite slabs (soaked and cleaned) on the bed, tap them with a rubber mallet, and check line and level with a straight edge.
4. Keep joints thin (1-2 mm) and straight, or use spacers.
5. After 24-48 hours, fill joints with cement paste, matching the colour, or epoxy grout.
6. Cure for 7 days, then clean and buff with a polishing machine. Seal the surface if required.

Advantages

• Very hard, durable and scratch-resistant.
• Resistant to heat, stain and weather; suitable for kitchens and outside.
• Natural attractive patterns, easy cleaning, long life.
• Does not need frequent re-polishing.

Disadvantages

• Costly material and skilled labour needed.
• Heavy, so the structure carries more load.
• Cold, hard and slippery when wet.
• Can crack or chip if impacted; porous types may stain without sealing.
• Colour and pattern vary between slabs.

Granite floor finish

Granite is a hard, natural igneous rock cut into polished slabs (18-20 mm). Slabs are laid on a 20-30 mm cement-sand mortar (1:4) bed with thin joints, then grouted, cured and polished. It is very durable, stain-resistant and gives a rich look. The disadvantages are high cost, weight and a slippery surface when wet. Used in lobbies, kitchens, staircases and public buildings.

Tile floor finish

Tiles are thin factory-made units of ceramic, vitrified, mosaic or terracotta, in sizes such as 300 x 300 and 600 x 600 mm.

• Laying: the base is cleaned and a 20-25 mm cement-sand mortar (1:4) bed spread. Tiles, soaked if ceramic, are pressed into a skim of cement slurry (or adhesive for a thin bed) and levelled with a mallet. Joints of 2-3 mm are kept with spacers.
• Finishing: joints are grouted with cement or coloured grout after 24 hours; excess is wiped off; the floor is cured for 3-7 days.
• Merits: wide variety of colours, easy cleaning, moderate cost, hygienic. Demerits: can crack under heavy impact, joints hold dirt.

   tile (8-10 mm)   =========
   adhesive/slurry  ~~~~~~~~~
   mortar 1:4       .........
   PCC base         ---------

Both are in-situ decorative floors of cement and stone, ground and polished.

Purpose of a suspended ground floor

A suspended ground floor is raised above the ground with a ventilated void beneath. It is provided to prevent dampness from rising into the floor, to ventilate and stop dry rot of timber, to give a warm floor surface, and to be used on damp sites, high water table or sloping ground.

Construction of tile flooring

1. Base preparation: the RCC slab or concrete sub-floor is cleaned of dust and mortar and wetted. A level line is fixed at the walls.
2. Mortar bed: a 20-25 mm cement-sand mortar (1:4) is spread, stiff and level, to the required slope.
3. Slurry coat: a thin layer of neat cement slurry (or adhesive) is spread over the bed.
4. Laying tiles: tiles are soaked (for ceramic), then laid from the centre or a corner. Each is pressed and tapped with a rubber mallet, checking line and level with a straight edge and spirit level. Spacers keep joints of 2-3 mm.
5. Grouting: after 24-48 hours the joints are cleaned and filled with cement or coloured grout. Extra is wiped off with a damp cloth.
6. Curing and cleaning: cured for 3-7 days, then cleaned with a mild acid wash and polished.

   tile 8-10 mm       =========
   slurry             ~~~~~~~~~
   mortar 1:4 (25)    .........
   RCC slab / PCC     ---------

The figure below shows a section of a solid ground floor with mosaic finish meeting an external brick wall.

        external wall (230 mm)
     |<---------->|
     |  plaster   |     skirting (mosaic, 100 mm)
     |            |  _/| 
     |            |_/__|__________ mosaic topping 12-15
     |            |....................... mortar 1:3, 25
     |            |ooooooooooooooooooo PCC 1:2:4, 100
     |   DPC 20mm |=====DPM (polythene)===
     |            |xxxxxxxxxxxxxxxxxxx hardcore 150
  GL |            |///////////// compacted earth
     |  plinth    |
     |  foundation|
     +------------+

Details from the top down

• Mosaic finish: marble/china pieces in cement paste, 12-15 mm, with glass or brass dividing strips, ground and polished.
• Mortar bed: cement-sand 1:3, 25 mm, to level and bind.
• Concrete bed: PCC 1:2:4, 100 mm, laid over the whole room.
• Damp proof membrane: polythene sheet, joined to the wall DPC to give a continuous barrier.
• Hardcore: 150 mm of brick or stone ballast, rammed.
• Compacted earth fill in 150 mm layers.
• DPC: 20-25 mm cement concrete (1:2:4) with waterproofer at plinth level, above the finished ground level (plinth at least 450 mm).
• Skirting: mosaic skirting 100-150 mm high on the wall, flush with the plaster, to protect the wall and give a neat edge.

A cement concrete floor is made of cement concrete finished with a cement-sand topping. It is cheap, strong, durable and fire-resistant, used in houses, godowns, schools and offices.

Method of construction

1. Preparation: the ground is cleaned, levelled and compacted. A layer of 100-150 mm hardcore (brick soling) is laid and rammed. For damp sites, a damp proof membrane is added.
2. Base concrete: cement concrete 1:2:4 (or 1:3:6 for light use), 75-100 mm thick, is laid in panels of about 2 m x 2 m using wooden or steel strips as screed guides. It is tamped and levelled.
3. Topping: while the concrete is still green (within 2-3 hours), a topping of cement-sand mortar 1:2 of 12-25 mm is applied.
4. Finishing: the surface is levelled with a straight edge and trowelled smooth. Neat cement slurry is sprinkled and finished with a steel trowel (punning) to get a smooth surface. Dividing strips can be removed and the joints filled.
5. Curing: the floor is covered with wet sand or gunny bags and kept wet for 7-10 days.

   topping 1:2 (12-25 mm)  ~~~~~~~~~~
   PCC 1:2:4 (75-100 mm)   ..........
   hardcore (150 mm)       oooooooooo
   compacted earth         //////////

Floors can be given a colour with oxide, or a hardener (iron filings, etc.) in heavy-duty work.

A common low-cost rural flooring in Nepal is the mud (earthen) floor with cow-dung/clay finishing, and an improved version is a brick-on-edge or cement-stabilised floor. The mud floor is explained here.

Construction of mud floor

1. Site preparation: remove the top soil, vegetation and loose earth from the floor area. Set the floor level at least 300-450 mm above the surrounding ground.
2. Filling: fill with good, clean soil in layers of 100-150 mm, with a bit of water, and ram it until firm.
3. Base layer: spread a 75-100 mm layer of well-mixed clay, sand and chopped straw (or cement-stabilised soil with 5-8% cement), and ram it.
4. Surface coat: a 10-12 mm coat of fine clay mixed with cow dung (or red clay, geru) is spread and smoothed with a wooden float.
5. Curing: keep it shaded and damp for several days, then let it dry slowly.
6. Maintenance: regular re-plastering with cow-dung, clay and water, usually every few days or weeks.

   cow dung + clay coat   (10-12 mm)
   clay + sand + straw    (75-100 mm)
   rammed earth fill      (layers of 150)
   original ground        //////////////

Precautions for durability

• Select well-graded, non-expansive, organic-free soil.
• Raise the plinth and provide drainage and a gentle slope away from the walls.
• Protect against rainwater with wide roof eaves and a plinth protection (apron).
• Ram thoroughly and avoid cracks; cure slowly.
• Add 5-8% cement or lime to stabilise.
• Re-plaster regularly with cow dung to seal cracks; keep termites away with treatment.

Flooring is the finish given to the floor surface over the structural base, to make it hard, durable, level, smooth and pleasant. It must resist wear, be easy to clean and be damp-proof.

Types of flooring

• Mud and brick floor.
• Stone floor (slate, kota, sandstone).
• Cement concrete floor.
• Terrazzo and mosaic floor.
• Marble and granite floor.
• Ceramic and vitrified tile floor.
• Timber (wooden board or parquet) floor.
• Linoleum, PVC, rubber, vinyl, carpet.
• Asphalt and glass floor.

Special floor finish: Terrazzo flooring

Terrazzo is a mix of cement and marble chips, laid as a topping 6-12 mm thick over a 25-30 mm bedding mortar (1:4) on a concrete base. Brass or glass strips divide it into panels of about 1 m x 1 m. After curing for 7-10 days, the surface is ground with carborundum stones (coarse, medium, fine), pores are filled with cement paste, and it is polished with oxalic acid and wax.

   chip topping 6-12  ~~~~~~
   mortar 1:4, 25     ......
   PCC 1:2:4, 100     ======
   hardcore           oooooo

Merits: smooth, hard, durable, easy to clean, many colours. Demerits: costly, skilled labour, may crack at joints and be slippery when wet.

Timber flooring consists of wooden boards, planks or parquet laid over joists or a base. The following must be considered.

• Choice of timber: well-seasoned, hard, straight-grained timber (sal, teak, sisau, uttis) free from knots and cracks; moisture content below 12-15%.
• Damp protection: the floor must be kept free from ground moisture, so a ventilated void under the joists (air bricks) and a DPC below wall plates are provided. At least 150 mm clear above the oversite concrete.
• Ventilation: air bricks at the external walls and a cross-ventilation path to prevent dry rot.
• Joist size and spacing: joists (e.g. 100 x 50 mm) at 300-400 mm c/c, with spans limited to 2-2.5 m. Use strutting or herring-bone bridging at mid-span to stop twisting.
• Boards: 20-30 mm thick, 100-150 mm wide, nailed with the heart side up, with tongued-and-grooved (T&G) joints and staggered end joints, over a joist.
• Fixing: secret nailing for a smooth surface; heads of nails punched.
• Treatment: preservatives and termite treatment on joists and boards; finishing with varnish or polish.
• Expansion gap: a small gap of 10-12 mm at the walls, covered by skirting.

   board (T&G)  ==============
   joists       |_|_|_|_|_|_|
   strutting      X  X  X
   wall plate  [==]       [==]
   DPC          --         --
   sleeper wall  |         |

Floor finish

The floor finish is the top layer of a floor, laid over the base concrete or slab, to give a hard, smooth, durable and attractive surface that resists wear and is easy to clean.

Wall cladding

Wall cladding is a non-structural covering of stone, tile, brick, timber, metal or glass fixed to the face of a wall (inside or outside) for decoration, protection from weather and sometimes for thermal and sound insulation. It does not carry the building load.

Common floor finishing materials

• Cement concrete / cement punning.
• Terrazzo and mosaic.
• Marble, granite, slate, kota stone.
• Ceramic and vitrified tiles.
• Timber boards, parquet.
• PVC, vinyl, rubber, linoleum.
• Carpet.
• Brick and mud (low-cost floors).

Tiles are thin, flat, factory-made units of baked clay or cement, used to finish floors and walls. They are hygienic, durable, easy to clean and available in many colours and sizes.

Floor tiles

• Types: ceramic, vitrified, mosaic (cement-marble chip), terracotta, clay, and stone tiles. Sizes: 300 x 300, 450 x 450, 600 x 600 mm; thickness 8-12 mm.
• Laying: on a 20-25 mm cement-sand mortar (1:4) bed over the base; tiles are tapped to a level, joints 2-3 mm, grouted next day, cured for 3-7 days.
• Qualities: low water absorption, abrasion resistance, anti-slip finish.

Wall tiles

• Glazed ceramic tiles (150 x 150, 200 x 300 mm; 5-6 mm thick) used in kitchens, bathrooms and toilets, up to a height of 1.2-2 m or to the ceiling.
• Fixing: the wall is plastered with a rough coat (1:4, 12 mm), wetted, then tiles are soaked and fixed with cement paste or adhesive in true line and level, with spacers. Joints are grouted with white cement.
• Merits: waterproof, clean, decorative. Demerits: brittle, cost, hollow spots if bonding is poor.