Finishes for walls

All walls that are constructed using a wet system require a surface finish of one type or another.
These wet constructed walls consist of blocks, bricks or stones laid with mortar and also cast in situ
concrete walls.
A wall finish may consist of painting, plastering and rendering, pointing the joints, Tyrolean application
or dry lining with plaster.

Purpose of a wall finish

1. Provide resistance to moisture penetration.
2. Give a more pleasant appearance.
3. Protect the structural wall from driving rain and sand storms.
4. Increase the fire resistance, sound and thermal insulation properties of the wall.

Finish Work
Interior walls should be resistant to wear and be cleanable; floors should be durable, comfortable, and safe
to walk on; ceilings should be relatively maintenance free.
Exterior wall surfaces must serve effectively as barriers against the penetration of water into the interior
of a building.
Rigid finish materials capable of spanning short distances may be applied to a supproting grid of linear
members. More flexible finish materials, on the other hand, require a solid, rigid backing.
Additional technical factors to consider include the acoustic qualities, fire resistance, and thermal
insulation value of a finish material.
Surface finishes have a critical influence on the aesthetic qualities of a space.
In the selection and use of a finish material, we should carefully consider its colour, texture and pattern,
and the way it meets and joins with other materials.
If a finish material has modular characteristics, then its unit dimensions can be used to regulate the
dimensions of a wall, floor or a ceiling surface.

Plastering and rendering

Plastering
The method of finishing wall surfaces with mortar to give a smoother and hygienic finish.
Plaster refers to any of various mixtures applied in a pasty form to the surfaces of walls or ceilings in a
plastic state and allowed to harden and dry.
This method of finishing surfaces with mortar will give a smoother and hygienic finish.

General preparation
 All first fixing, electrical and plumbing pipe must be installed.
 Channels, chases or any other cutting through the wall must be cut prior to plastering

Procedure of plastering different background

Concrete background
 Hacking the surface to create key for the plaster.
 Rub off surface using wire brush.
 Wet the surface with water until well soaked.
 Install plaster dots approximately 150mm square on the whole surface being vertically plump and
on the same plane.
 Apply 1st coat of plaster if required and scratch the surface to form key for other coats, 2rd coat is
applied if necessary and left to dry before final coat is applied.
 Install mortar screeds being plump with the dots at approximately 2m centers.
 Fill up between screeds and rub off the surface with the straight edge.
 Final finish is achieved by finishing with the wooden float and steel float respectively.
 Masonry (bricks, blocks, stones)
 Rake off the joints about 15mm deep.
 Rub off the surface using wire brush.
 Dampen the surface of the wall.
 Proceed as for concrete surface.

Timber framed wall

 Fix the 20x12mm timber laths onto the framework leaving a gap of about 6mm between them or
fix the metal fabric onto the timber framework.
 Apply mortar slowly using a steel float ensuring no mortar droppings inside the framework.
 Apply several coats until required smooth surface is achieved.

Plastering procedure
Plastering failures
1. Popping, Pitting and Blowing
Caused by unsound lime that has not been staked properly or over troweling the surface thereby creating
air bubbles on the surface.
2. Poor adhesion
Caused by
 High suction of the backing
 Too rapid drying out
 Inadequate key and
 Incorrect choice of plaster
3. Cracking / Crazing
Caused by
 Shrinkage on drying out
 Improper choice of plaster and
 Inadequate curing.

4. Ceiling collapse
Caused by insufficient key on the plaster.

Rendering
Rendering is used on exterior walls and in areas subject to wet or moist conditions.
External rendering requires the following characteristics.
1. Attractive appearance and colour
2. Durability
3. Resistance to moisture penetration
4. Frost resistance
5. Uniform weathering
1. Appearance
It depends on the choice of finishing technique e.g. rough cast, pebble dash. Machine applied etc.
Colour is usually applied by use of colored cements or by incorporating colored aggregates in the mix of
the final product.
2. Durability
It depends upon the degree of adhesion of the rendering to the background over the whole of the surface,
the detailing of the sills and copings, the composition of the mix, the standard of workmanship etc.
3. Resistance to moisture penetration
Depends upon whether the rendering after setting contains air cracks which are caused by strong
rendering that has crazed. These allow water to penetrate.
4. Frost resistance
Will depend on whether or not the rendering will be saturated in any part during frost. This can be
controlled by sills and copings.
5. Uniform weathering
Depends on the texture of the finished surface, the amount of pollution in the atmosphere and amount of
overhang to sills, copings etc.

Typical mortar mixes for rendering

Cement Lime Sand
1 - 4
1 1 6
1 - 6
1 2 9
Tyrolean finish
It is one very popular finish and has a rough pleasing appearance,
It may be colored according to taste or applied in the natural grey colour of ordinary Portland cement.
A wall which is to receive Tyrolean finish is first of all rendered with one or more coats, depending upon
how flat and even the wall was built. This is done in order to obtain an even thickness for the Tyrolean
finish.

Advantages
a. Driving rain and sand storms do not affect the surface texture
b. Does not require periodic renewal
c. The rough, ragged appearance discourages vandals and children from defacing the wall
d. Fairly easy to apply and cheap if ordinary cement is used.

Fig 4 Tyrolean finish

Wall Tilling

Wall finishes
Ceramic Tiles
Ceramic tiles are relatively small, modular surfacing units made of clay or other ceramic material.
The tiles are fired in a kiln at very high temperatures. The result is a durable, tough, dense material that is
water-resistant, difficult to stain, and easy to clean; its colours generally do not fade.

Ceramic tile is available glazed or unglazed. Glazed tiles have a face of ceramic material fused into the
body of the tile, and may have glossy, matte, or crystalline finishes in a wide range of colours.
Unglazed tiles are hard and dense, and derive their colour from the body of the clay material. These
colours tend to be more muted than those of glazed tiles.

Types of ceramic tiles

Glazed Wall Tile
Glazed wall tile has a nonvitreous body and a bright, matte, or crystalline glaze, used for surfacing
interior walls and light duty floors.
Exterior tiles are weatherproof and Frostproof, and can be used for both exterior and interior walls
Ceramic Mosaic Tile
Ceramic Mosaic Tile has a porcelain or natural clay body, glazed for surfacing walls or unglazed for use
on both floors and walls. Porcelain tiles have bright colors, while natural clay tiles have more muted
colors.
To facilitate handling and speed installation, small tiles are usually faced with paper or backed with mesh
to form 305x305mm or 305x610mm sections with the proper tile spacing.

Quarry and Paver Tiles

Quarry tile is unglazed floor tile of natural clay or porcelain. The tiles are impervious to dirt, moisture,
and stains, and resistant to freezing and abrasion.
Pavers are similar in composition to ceramic mosaic tiles but thicker and larger.
They are weatherproof and can be used on floors subjected to heavy duty loads.

Ceramic tile application

The major problem in tiling work is bond failure. There must be adequate mechanical key provided by the
background and therefore the plaster should be left unsmoothed.
The unglazed back of the tile is porous and absorbs moisture very fast. It is therefore advisable to soak
tiles in water before fixing.
Tiles should not be fixed on thin backgrounds unless they are made adequately rigid, as tiles on such
backgrounds are liable to come loose.
Tiles tend to be very fragile and difficult to cut by manual means. The work must therefore be carefully
set out before the fixing operation is commenced.

Fixing procedure
1. Hack the wall and clean thoroughly if surface is smooth
2. Set out the work, starting from a corner, making sure that all odd pieces are placed at a corner and
at the base of the wall
3. Bed a flat piece of lath to a perfect level at the base of the wall to receive the first course of tiles.
This may not be necessary with a finished floor
4. Clean down the wall to remove dust, and spray water on it
5. Soak the tiles in water
6. Mix mortar: 1-part cement to 3 parts sand. Fixing of tiles is nowadays done with special mastics
7. Butter the tile bed evenly with mortar and press on to the wall, tapping it slightly into position.
Ensure that the mortar or mastic covers the entire bed of the tile. The practice of dotting the bed
of dotting the bed of the tile with mortar or mastic should not be employed as it eventually leads
to bond failure.
8. Allow as small a joint as possible between tiles and ensure plumb and flatness by using a spirit
level and a straight edge. By moving the face of the fingers over the edges of newly fixed tiles,
one can easily tell if the edges are flat to each other or not
9. Rub the joints flush with a piece of soft waste cloth
10. Clean the tiles after setting and polish as a final operation
11. Clean the tools and working area
 Fig 5 Wall detail

Fig 6 Floor detail

Pointing and Jointing

Pointing
This is the name given to the method of finish the wall joints receive after the wall has been built.
There are three types of pointing, each of which is carried out after the joints have been raked out and
thoroughly cleaned. These are
a. Weather pointing
b. Weather struck joint
c. Tuck pointing
Jointing
This is the name given to the treatment of the joints as the building of the wall proceeds.
Types of jointing
a. Flush
b. Tooled
c. Recessed
The advantage of jointing is that one worker does the job and so the work is faster and an even colour is
obtained

Procedure for Flush Jointing

After a reasonable number of courses or portion of block wall have been laid and corrected i.e. levelled;
plumbed and aligned, a piece of clean flat wood is rubbed over the fresh joints.
While the rub is being used, joints with insufficient mortar are filled, so that truly flush joints can be
obtained.
Portions should be finished soon after laying to avoid drying out.

Procedure for Recessed Jointing

After the rubbing of the fresh joints with a clean flat wood, a round metal rod jointer is used.
The jointer is pressed against the fresh mortar and drawing it to and fro.
A spirit level is held against the joint to ensure that the recess is perfectly horizontal and perpends are
true.
The finished work is wiped with a soft brush to remove all pieces of mortar drops.