Masonry, plaster, timber and metallic finishes are subject to knocks resulting in chips, indentations and abrasions. Paintwork and other surface finishes become marked, scratched and stained.
A chipped or broken brick or block in facework should be cut out and replaced with a sound unit. In plaster, clean, moisten and patch with plaster or a proprietary patching material.
In timber, in the body of the surface, fill small holes with proprietary filler. On arises and for large holes, cut out the block with matching timber or veneer.
In metal, replace the component. Some shallow indentations in a painted surface can be filled with proprietary metal filler.
After patching or filling, paint as described in PAINTING.
To achieve a uniform finish, it is important that after patching a wall or ceiling and painting the patched area, then the whole of that wall or ceiling containing the patched area shall he included in the final coat.
Soiled paintwork is washed or rubbed down and repainted in one or two coats.
Flaking or peeling paintwork must be scraped or burnt off, and the base surface treated as for new work. Paint used in damp areas such as Bath Rooms should be fungus resistant, such as oil based enamel. Damaged carpet, vinyl and laminated plastic can be partially replaced. Proprietary acrylic composition bench tops can be repaired.
Many fittings, such as cookers, hot water units and air conditioning units deteriorate with age to the point where replacement is a more attractive alternative (newer models, features etc) than to continue with an older model and perhaps incur costly maintenance. Ten to twelve years is a reasonable life for these items.
Structural breakdown usually derives from an original avoidance fault. The life of finishes, both natural and applied, may be more limited, but can be likewise shortened by errors or omissions in original building. Primarily these problems are:
Entry of dampness.
Breakdown of adhesion of applied finishes.
Entry of dampness is caused by:
Failure or absence of damp course of flashing.
Incorrect location of damp course or flashing.
Bridging of cavity.
Fracture or blockage of water or drainpipes
Horizontal damp course can be replaced and/or inserted in existing walling by removing masonry coursing in alternate 700 mm to 800 mm lengths, or sawing out the joint with a disc or chainsaw, to allow replacement. After replacement mortar has set, remaining intervening panels are similarly treated. Each damp course section must overlap the piece adjoining.
The principals of damp proof coursing and flashing are illustrated in BRICKWORK AND BLOCKWORK.
The cavity in external perimeter masonry walling must be maintained.
Cavity bridging usually occurs by accumulation of mortar at the bottom of the cavity or on cavity ties, and is rectified by the physical removal of bricks as necessary to give access to the cavity, to permit cleaning out of the mortar.
Inadvertent closing of the cavity by masonry is rectified by sawing through and inserting a positive mechanical barrier of damp course material. Moisture entry around door and window openings is usually due to absence of. or incorrectly located flashings.
In metal framed windows, dampness at sill level is sometimes caused by absence or blockage of weep holes which allow water caught in the sill channel to discharge. Flashing problems can sometimes be overcome with mastic pointing at the junction of the frame and wall externally.
There is no substitute for a properly installed positive mechanical flashing.
Most metal roof leaks originate from perforations through the roof-pipes, ventilators, aerial fixings and the like. Small holes and short laps in sheet roofing must be sealed, and flashing made watertight. The minimum pitch and fixings must always be to Manufacture’s recommendations.
Other causes of leaks are:
Inadequate side, apron and gutter flashing.
Cracked or displaced tiles.
Inadequate lapping of roof sheeting.
Unsealed laps at very low pitches.
Pop-riveting of ridge and hip cappings in lieu of bolts or screws.
Inadequate pointing of hip and ridge tiles.
Gutter and down pipe overflows.
Gutters should be checked throughout the year especially before winter to ensure they are kept free of blockages.
The greatest of care must be taken when building with concrete, because any serious or continuing problem is usually solved only by the costly process of removal and relaying. Principal maintenance problems are:
Slab surface defects
Cracking can be either structural (i.e. right through the element), or surface. In concrete on earth, structural cracking may be caused by uncontrolled linear drying shrinkage, or earth movement. See CONCRETE for notes on contraction joints and mesh reinforcement.
Rectification is by saw-cutting out a panel and relaying with ruled, and if required, pointed joints. In suspended concrete, structural cracks result from improper or inadequate design, misplacement of reinforcement, and concrete below required design strength or excessive loading during curing period. The remedy for structural failure is removal and reconstruction.
Surface defects may be drying shrinkage cracks in topping and surface powdering.
Shrinkage cracking in topping is usually in the form of crazing, and whilst not structurally critical, is unsightly. For an exposed finish, rectification would require hacking off the topping and laying a new topping as described in CONCRETE.
Surface powdering is caused by a low cement aggregate ratio, incorrect proportioning of aggregate fines, excessive water in mix, or excessive addition of pigment. Minor powdering can be arrested by flooding the surface with a proprietary hardening agent.
Major powdering on an exposed surface would require removal and relaying of the top 25 mm to 35 mm.
Spalling is caused by expansion of rusting reinforcement not sufficiently covered, or by decay of quartz or other impurities in concrete. Replacement or patching would be required.
Corrosion of concrete by external factors (chemical attack by sugars or acids) is rarely a problem in domestic buildings.
Cracks in walls may result from:
Uncontrolled thermal movement in long walls.
Inadequate support over openings.
Movement occurs in plastic clayey soils as a result of moisture and thermal changes. Subsidence or pressures resulting will in the absence of adequate foundations, cause cracks in walls.
Thermal movement in long masonry walls will cause cracking in the absence of control joints. Absence of, or inadequate support can result in cracks at the heads of openings.
A crack can always be anticipated at the junction of brickwork and concrete. This should be controlled with a “bond breaker” membrane. Rectification of above faults may, dependent on severity, require:
Saw cutting in new control joints.
Removal of brickwork or block-work both sides of crack and re laying.
Raking back cracked joint 35 mm and pointing with mastic joint sealer.
External paintwork is broken down by the action of sunlight, air and moisture. Full deterioration may take from 3 to 10 years, manifested by powdering, flaking or peeling.
Powdered areas may be rubbed down and repainted in preferably 2 coats.
Flaked or peeling paint must be scraped or burnt off to the original surface, which is then treated as for new work.
Adequacy of protection will depend on paint film thickness and opacity.
Damp courses, flashing, roof sheeting, gutters and plumbing piping in buildings are all subject to corrosion by either chemical or electrolytic action.
For example, unprotected metallic damp-coursing is subject to the corrosive action of mortars, and electrolytic corrosion will occur in the junction of copper and steel piping. In replacement, ensure that the attacked metal is adequately insulated with a neutral material. In new building work, steel exposed externally will rust unless adequately protected, according to conditions, and particularly coastal.
See STEELWORK for notes on protective coatings for steel.
Improperly slaked or hydrated lime can result in powdering and fretting of mortar due to the continuing hydration process. Rake out the soft mortar 25mm to 40mm deep and point up with strong composition mortar. Fretting of actual brick surface can result from the trapping of salts in the pores of bricks during manufacture, which becomes active with moisture. Fretted bricks must be replaced.
Timber, properly installed in a building is a strong, durable and decorative material.
Problems usually originate from building faults or neglected protection.
Inadequate paint coverage or lack of maintenance will result in external timber such as posts, beams doors and window frames, door faces, barge boards, fascias etc, developing surface cracks and opening up joints. If deterioration has not advanced too far, these items can be repaired.
Lifting of timber flooring. Caused by no allowance in installation for seasonal movement. Remove centre and outer boards. hammer back flooring, reduce outer boards and replace. Improve sub floor ventilation. Lifting of floor framing from stumps.
Caused by no allowance for seasonal movement, and poor ventilation. Gain access to underfloor, saw cut bearers over piers to let down, and improve sub floor ventilation. Termite attacking timber.
Karri near the ground is particularly vulnerable. Building sites require pretreatment against termites in accordance with AS 2057 1981. Rectification includes Replacement of affected timber and specialist treatment. Because nests can be under concrete floors treatment may require boring through concrete or cutting trap door in floor.
Shrinkage cracking bowing and twisting.
The visible evidence of green and unseasoned timber, must be replaced with sound, seasoned members.
This is a furry powdery deposit of water soluble salts which form on the surface or brickwork. Water soluble or acid solution salts of vanadium, iron or manganese in film can also form on the surface of brickwork, showing as a stain. Drips from unsealed hardwood can also stain light colored masonry. The white powder of efflorescence is water soluble, can be washed off, and will eventually disappear.
The green and yellow vanadium stains which sometimes appear on cream brickwork respond to chemical treatment such as oxalic acid, hypochlorite type bleaching agents and caustic soda in different cases. Note that hydrochloric acid should not be used on cream brickwork because it tends to set the vanadium salts in the surface and turn them black. Timber stains usually respond to a solution of oxalic acid in water, or a household bleach based on sodium hypochlorite. Hose down after chemical treatment.g
Porous masonry and some porous plastic paints, for example, PVA, are susceptible to fungus attack in conditions of sustained moisture or humidity. Proprietary preparations such as those containing Sodium and Calcium Hypochlorites, and Sodium carbonate can be used to remove the mildew stain. The application of silicone sealing, or an impervious oil based paint will inhibit regrowth.
Breakdown of adhesion will result in loosening and detachment of:
Ceramic tiles from floors and walls.
Vinyl tiles and sheet from floors and walls.
Timber mosaic and parquet from floors
Papers and vinyl from walls
Laminated plastics from backing
Causes of breakdown include:
Ceramic tiles bedded in cement mortar – sub standard mortar, tile suction (i.e. tiles not soaked before laying), no provision for thermal movement in restrained positions, pre-setting or drying of screed.
Rectification requires relaying to correct procedure, and incorporation of mastic filled control joints as may be necessary.
Moisture in sub-surface. This can cause lifting of adhered ceramics, vinyl and timber mosaics. Testing can establish adequacy of dryness of sub-surface. Laying must be carried out with the recommended bonding agent.
Wall papers and vinyl’s lose adhesion because of excessive suction of the subsurface. Porous backgrounds require sealing.
Rigid PVC piping used externally will break down under prolonged exposure to heat and sunlight. Mechanical impact to plastic products can cause fracture. UPVC should therefore be protected from impact damage and direct sunlight. Replacement is readily effected. Detached contact-adhered laminates are rebonded and cramped.g