Pointers For Homeowners
Cement-Sand and Gypsum Plaster Coatings
The type of wall finishes covered here are:-
- Facing bricks
- Rockstone or other textured coatings
- Ceramic tiles
- Wallpaper
- Cement-Sand and Gypsum Plaster Coatings
- Painting
The pointers given below will help you check on the quality of
materials and installation methods.
Facing Bricks
Facing Bricks are used to erect external walls. They are
normally not plastered. A good finished brickwall is shown in Fig.
1.
Fig. 1 Good facing brickwork for an external wall
Checks For Material Quality
Facing bricks are better in appearance than fair-face common bricks.
-The bricks should be uniform in shape with no warping.
-The colour tone should be even and identical.
-There should be no chipping at the edges or cracks or stain marks on the brick surfaces.
-Check than the brick stretcher and header faces are glazed.
-Defective bricks with hollow sounds when two pieces are knocked together should not be used.
Checks For Quality Work
-In the erection of the brickwall, a light gauge wire mesh or expanded metal should be laid in every fourth course or bricklaying. The wire mesh should also be used at locations in contact with a concrete surface such as a concrete column or beam.
Fig. 2: Sketch view of erecting a brickwall the light-gauge wire mesh or expanded metal laid at the bottom of the fourth course and the damproofing course at the bottom of the first course.
-Ranking joints are not acceptable as these are only applicable to common brickworks which required plastering. Joints for facing brickwork should be 10mm wide with pointing.
-Proper pointing using 1:1 ratio of cement and fine sand mixture should be used instead of cement slurry which will crack at the bedding joints.
-A damproofing course should be laid at the bottom of the first bricklaying course for an internal brickwall. In the case of an external brickwall, it should be laid in the course which is at 150mm above ground level. A damproofing course should also be laid in the coping between the top of the brickwall and the concrete beam or slab above it.
-There should be no cracks at the edges of the bricks and the tone and colour should be uniform in the erected brickwall.
-Ties in the form of galvanised wire and straps should be provided to window or door frames built into the brickwall.
-There should be consistent bedding with no see-through joints.
Besides plastering, textured coatings may be applied onto walls of ceilings as finishes. There are many types of textured coatings which are applied by a spray-gun. An example of a textured coating is the Rockstone sprayed finish.
Checks For Material Quality
-Two sealer base coats which are applicable for masonry surfaces are necessary to create a new base to bond better with textured coating.
-Use products from same production batch. Do not mix materials of different brands.
-The materials should not be exposed to direct sunlight for too long and aged materials should not be used.
Checks For Quality Work
-The base must be clean, dry and free from dust, oil, laitance and all forms of contaminations.
-No cracks and peeling should occur in the applied textured coating.
-No air voids should be trapped beneath the textured coating.
-Textured coating should not spill over onto door and window frames.
-Ensure poor construction joint and uneven surfaces do not exist.
-Ensure dampness does not exist on the textured coating.
Ceramic tiles for walls are usually used in the kitchens, bathrooms and other wet areas. They come in various colours, designs and sizes. Glazed tiles are often used for walls.
Checks For Material Quality
-Tile size should be consistent to within 1%.
-Cracked tiles and tiles with chipped edges should not be used.
-Correct tile adhesive should be used.
Checks For Quality Work
-Paint droppings and painting over tile surfaces near edges should not occur.
-Tiles at pipe joints and supports should be properly trimmed and filled.
-Surfaces of the tiles should have no crazing cracks.
-Where ceiling and wall meets, full-sized pieces of tiles should be used.
-Tiled surfaces should be level, even (uneveness should not exceed 4mm in 0.6m length of tiled wall surface in any direction), plumb (vertical deviation should not exceed 3mm in 1.2m height) and square. Edges should be checked for straightness.
-Joints of tiles normally not more than 3mm wide, should be properly pointed and its arrangement should result in proper alignment.
-Drummy or hollow sound should not occur when the tiles are tapped with the fingers.
Wallpapers vary considerably in design and cost. They come in rolled sheets and are glued to walls and ceilings using adhesive.
Checks For Material Quality
-The wallpapers should be from the same stock to avoid any non-uniformity.
-Check for uneven colour distribution and fading.
-Ensure that no insects are present on wall papering materials.
-There should be no stain marks and badly folded wallpapers should not be used.
Checks For Quality Work
-The base should be free of dust, oil, dampness and mortar splashes.
-Check that no bubbles exist on the underside of the laid wallpaper.
-Joints at corners and edges should not be crumpled, warped or curled. They should be properly lapped and pattern coinciding.
-Dirty stains and marks on wallpaper should not exist.
Cement-Sand and Gypsum Plaster Coatings
Plastering is usually carried out for walls and ceilings to create a smoother finish. Normally a cement-sand plaster or a gypsum plaster is used.
Checks For Material Quality
-For normal plastering, cement-sand plaster finish is used. The cement used should be free from lumps and the silt content in the sand should not be more than 3% to minimise cracks due to drying shrinkage.
-To achieve a better plaster finish, gypsum plaster is used. The powdered gypsum must not form small tiny lumps.
-Only gypsum plaster which have not set within 20 minutes should be used.
-Use clean water to mix the gypsum plaster.
-Hemihydrate gypsum plaster known commercially as 'Plaster of Paris' should not be used as a plastering material. It may be used for patching or other purpose where a rapid set is required.
Checks For Quality Work
-Cement-sand plaster may be used for concrete hollow blockwall and brickwall. One undercoat of cement-sand ration 1:2.5 and at least one finishing coat of cement-sand ratio 1:3 should be used.
-The thickness of the undercoat and the finishing coat of cement-sand plaster should each be about 9mm for internal walls and 12mm for external walls.
-For gypsum plastering, a minimum of two coats each of thickness 1.0mm should be used.
-For smooth wall surfaces, a light gauge wire mesh should be used to apply on the thick cement-sand plaster. For gypsum plastering, this may not be necessary as the coats are thin.
-Each plaster coat should be allowed to dry out before the next coat is applied. For cement-sand plaster, a period of about one week is advisable whereas for gypsum plaster this period would be shorter.
-Proper tools like the trowels and plastering boards should be used. (Fig. 3)
Fig. 3 The premixed gypsum compound, trowel and plastering board used for plastering work.
-No hollow sound should exist when the hardened plaster is subjected to a finger's tapping.
-Ridges or trowel trackmarks should not be visible.
-There should not be any patchy stains or paint drops over the plaster surfaces.
-There should not be any tiny hairline cracks or sand holes in the plastered surfaces.
There are different types of paints for both exterior and interior use for wall and ceiling finishes.
Checks For Material Quality
-Use paints only from the same batch. For internal use, Vinyl Silk paints are suitable. Paints should not be over diluted with thinners.
-Algae and fungus resisting finishing paint coats are necessary on potential damp surfaces.
-Check that an aluminium wood primer is used over new timber surfaces. Similarly, anti-rust primer should be used for metal surfaces.
-Sealer coats are also necessary over new plastered surfaces.
-Partially consumed paints which have been kept in containers for too long a period should not be used.
-Proper and clean painting accessories like brushes and rollers should be used. (Fig. 4)
Fig. 4 The various tools, equipment and accessories required for a good painting job.
Checks For Quality Work
-Plaster cracks and blemishes should be properly filled before painting.
-At least two coats of paint should be applied.
-Ensure the surfaces to be painted are even with smooth edges and sound in order to bond well to the substrate. This can be checked by a scotch tape pull off test. No paint coating should stick on the scotch tape when it is pulled off the wall.
-The painted walls or ceilings should be of uniform colour and tone.
-Mortar stains should be removed prior to painting and painting should not extend onto door and window frames.
-Check that the type of finish whether matt, semi-matt or gloss have been achieved as specified.
-Check for peeling and wrinkling on paint surfaces. Use the hand to check for chalkiness on the painted surfaces.