Repair to Spalling Concrete and Ceiling Leak
This Technical specification shall be read in conjunction with the Standard Specifications and Supplementary Specifications. In case of discrepancy between this Technical specification and the Standard Specifications, the Supplementary Specifications shall take precedence, followed by the Technical Specifications.
WORK PROCEDURES AND REPAIR METHODS
The Contractor shall comply with the approved material list, work procedures, and repair methods stated in this Specifications. These specifications and the accompanied guide drawings may be amended or added any time as deem fit by SO Rep. Any modifications on the guide drawings by the Contractor shall be approved in writing by the SO Rep. The Contractor shall provide the training to their workers and procure equipment for such changes. All cost, expenses and sums incurred by the Contractor howsoever arising or consequent upon shall be deemed to be included in the Contract.
Administrative charges as specified in Appendix 4 herein shall be imposed on the Contractor for any failure to comply with this clause.
PRECAUTIONS IN EXECUTION OF WORKS
The Works shall be carried out in the order that may be directed by the SO Rep so as to minimize the inconvenience caused to the flat owners, the affected parties or the public. The Contractor shall provide adequate barricades and warning signs and take such safety measures as may be required to comply with the requirements of the relevant authorities.
As the existing buildings are occupied, the Contractor shall take every precaution to prevent injury to person, damage to properties, excessive noise or vibration and dust nuisance by appropriate means. Permission to enter occupied premises must be arranged and obtained by SO Rep together with the Contractor. In the event of any dispute, the Contractor shall indemnify the HDB from claims arising thereof.
Polyethylene sheet, corrugated sheet, cardboard, and/or canvas sheet (hereinafter referred to as “Protective sheet”) shall be used to protect the flooring and furniture. The site where Works is being carried out shall be cordoned off to confine the dust generated from the Works.
The Works shall be carried out with necessary precautions to avoid damage to the adjoining parts of the structure or adjoining property. All parts disturbed or damaged during the execution of the Works shall be repaired or replaced to match its existing condition at the Contractor’s own expense.
All Works and making good shall be executed with materials and workmanship to the satisfaction of the SO Rep. Areas stained by the Works shall be washed or repainted.
EXISTING FINISHES, FIXTURES AND FITTINGS
Hacking of Existing Finishes
Where hacking of existing finishes is required, Contractor shall use light pneumatic/electrical breakers of gross weight less than 7kg. The Contractor shall plan the Works so that not more than 2 breakers are used at any one time for the Works in one building blocks unless otherwise approved by SO Rep.
Flat Condition Survey
Upon SO Rep’s instruction, prior to the commencement of Works, the Contractor shall visit the flat jointly with the SO Rep and advise the flat owners of the fixtures, fittings (including furniture, electrical appliances, suspended ceiling system etc.), wall and floor tiling/finishes that are likely to be affected by the Works, possible disruption of services and other imminent inconveniences.
When SO Rep see fit, all existing defects, type and conditions of fittings, fixtures, wall and floor tiling at the repair areas and adjacent properties within flat owners’ flats shall be properly recorded by way of notes, sketches and/or photographs, so as to avoid any disputes on feedback of damages caused by the Contractor during/after the execution of the Works. The records of items within the flats shall be jointly endorsed by the Contractor, SO Rep and the flat owners. The original copy of the records shall be retained by the SO Rep with a copy kept by the Contractor.
Where damage to fixtures and fittings is inevitable, the Contractor shall identify the items so affected, the expected extent of damage and provide reasonable explanations to the satisfaction of the SO Rep.
Removal and disposal of Fittings and Fixtures
The removal and disposal of existing fittings and fixtures, such as long bath, shower tray, vanity top, cabinet, shower screen, door track for sliding door etc. which may obstruct the Works shall be included in the Contractor’s Contract Rate.
Replacement and Reinstatement of items
For fittings and fixtures originally provided by the HDB (e.g. shower screen, toilet door, suspended ceiling system etc.) that are required to be reinstated, the Contractor shall exercise due diligence and care during the removal process. Unless otherwise specified, the Contractor shall be responsible for the reinstatement, rectification, making good, replacement as required of these fixtures and fittings.
For fixtures and fittings not originally provided by the HDB, the Contractor shall obtain the flat owner’s agreement to replace or reinstate such fixtures and fittings and provide a reasonable quotation for flat owner’s consideration through a HDB system or other method approved by SO Rep before carrying out the Works. The Contractor shall ensure that their quote is reasonable. Any negotiation and agreement with the flat owner is strictly on a private basis. The SO Rep will not be obligated to resolve any dispute for the Contractor.
The Contractor shall be responsible for any wall tiles, floor tiles and attachments damaged or removed or otherwise affected either directly or indirectly by or in connection with the Works. The reinstatement, reinstallation, rectification, making good or replacement shall be done to a reasonable standard and to match as closely and in every respect with the existing surroundings, to the satisfaction of the SO Rep.
The Contractor shall be responsible for the Works or replacements of fixtures and fittings at the lower floor unit and any surrounding units, if the damage is caused by the Works.
REPAIR OF SPALLING CONCRETE
Preparation of Works
Upon the instruction of the SO Rep, the Contractor shall mark out the area to be repaired and seek the approval from the SO Rep before proceeding with the Works. The Contractor shall use only hammer and chisel, or light pneumatic/electric tools with impact energy not greater than 4Nm to remove the concrete to avoid the shattering effect on the building. For large area of defective and unsound concrete, the Contractor shall take all necessary safety measures prior to the commencement of the Works.
Patch Repair Method
Patch repair method shall be used for repairing spalling concrete, unless otherwise specified by the SO Rep. Generally, polymer modified cementitious mortar shall be used to replace the unsound concrete. The SO Rep may specify that epoxy mortar be used for toilet area or where the cover to the exposed reinforcement is less than 10mm.
The Work shall be carried out according to the method described in Annex A herein.
Pressure grouting may be specified by the SO Rep if the spalling concrete to be repaired is on critical structural members or when the spalling concrete is extensive. The repair procedure is shown in Annex B herein. For such repair, it is important to consider the adequacy of the adjacent structural members during the execution of the Works.
REPAIR OF CEILING LEAK
General Repair Method
Most of ceiling leak shall be repaired by re-waterproofing the floor slab surface and with minimum 200mm upturn at the wall surface. In most cases, it involves the removal and reinstatement of floor tiles, wall tiles, squat pan/pedestal pan. It generally takes about three (3) to four (4) working days to complete the Works depending on the availability of the flat owners and/or affected parties or as instructed by the SO Rep. Unless otherwise stated, the scope of Works under this Contract shall include the conversion of existing squat bowl to pedestal pan.
Re-Waterproofing The Slab Surface
The procedures for re-waterproofing the slab surface is as follow,
- Moisten the area to be hacked prior to the commencement of the hacking work so as to minimize dust. Remove existing tiles and screeds from the floor with approved hacking tools, including all existing kerb within the Site. Hack further down to a maximum of 50mm into the mortar in-fill concrete around the sanitary pipes and floor trap. The exposed concrete shall be cleaned and free of any sand, loose mortar, laitance or any other substrates that may affect the bonding of screed to existing surface. Squat pan/pedestal pan shall be removed unless otherwise agreed by the SO Rep. The bottom course(s) of the wall tiles shall be removed to a minimum of 200mm high, measuring from the exposed concrete floor surface to the joints of the tile. The wall tiles shall be cut at its joint. Use a hammer and a chisel to remove those tiles near the stack pipe area to prevent damages to other parts of the flat.
- Apply non-shrink grout to the surface receiving the membrane and areas around the pipes and floor trap so as to level the surface. The material used must be approved by the SO Rep. After laying the non-shrink grout, at least two hours shall be allowed for it to cure and harden. 45 degree fillet with about approximately 10mm leg length shall be formed by non-shrink grout to the edge between the floor and wall. Proper curing shall be allowed for it to harden.
- Apply quick-set liquid-applied flexible non-cementitious water-based waterproof membrane or other approved flexible water-based waterproofing membrane in two coats. The method of application and the curing time between the two coats shall be in accordance with the manufacturer’s instruction. The waterproof membrane shall be applied to the entire concrete floor with an upturn of minimum 200 mm onto the lower end of walls and minimum 100mm onto the pipes adjoining to the floor.The upturn onto the entrance kerb shall cover its entire hacked surface. As and when requested by SO Rep, the existing topmost tiles at the entrance kerb shall be removed, followed by waterproofing membrane, prior to the laying of matching tiles, at no additional cost.Upon request by SO Rep, the Contractor shall provide measuring gauges for checking of the wet film thickness at the time of application. The membrane shall be cured for a period of not more than 3 hours or as specified by the manufacturer.For situation where the bathroom and WC are separated by a wall and the discharge of water to the floor trap is by means of a weep hole, the Contractor shall ensure that waterproofing membrane is applied all-round the weep hole. Upon the instruction by SO Rep, the Contractor shall lay sanitary piping and floor trap for discharge of water and this cost shall be deemed to have been included in the Contract Rates.
- Use pre-packed waterproof screed to form the mortar bed with minimum thickness of 15mm with a fall evenly towards the water outlet. Proper mechanical mixer shall be used to mix the screed and the constituents shall be added in a manner approved by the SO Rep.
- Install floor trap with a new UPVC grating adaptor that includes all necessary fittings, elbow, water pipes for connecting to existing basin / sink, shower tray or long bath. If there are site constraints to install the adaptor, the Contractor shall propose alternative method for the SO Rep’s approval.
- Tiling and pointing shall be carried out after the screed has fully cured and hardened for at least 12 hours. Approved proprietary coloured tile grout shall be used for pointing of tile joints. A maximum of 3mm gap shall be allowed between the tiles.
- All discharge pipe shall be laid on the floor surface and covered by concrete kerb with matching tiles, unless otherwise instructed by the SO Rep to embed the pipes,
- If there is a pedestal pan, it shall be installed after tiling. Anti-fungi sealant shall be used to seal up the joints of the pedestal pan and the floor. Coloured pedestal pans shall also include Burgundy and Black colour and the cost of these pedestal pans shall be deemed to have been included in the Contract Rates.
Repair Method To Ceiling Leak For Upgraded Toilets/WC
In the event when a ceiling leak case had undergone HDB upgrading such as Main Upgrading Programme (MUP) or Home Improvement Programme (HIP) etc. or undergone any conversion from squat pan to pedestal pan by HDB or the flat owners and/or affected parties, the Contractor shall hack the porous concrete infill and reinstate with non-shrink grout including installation of necessary pipe fittings.
For situation where there is a need to hack-through the sunken slab for replacement of pipe, the Contractor shall propose the method statement for SO Rep’s approval before execution of Works.
The Contractor shall confirm with the flat owners and/or affected parties whether they require the repaired floor level of the toilet / bathroom etc. to remain the same as their original floor level during the time of survey. The top-up of concrete shall be included in Contractor’s scope of Works.
Repair Method To Localised Ceiling Leak
Localised ceiling leak may be treated according to the procedure shown in Annex D using nonshrink grout. This method of repair is suitable when the leak is confined around pipe due to localised porous in-fill concrete.
When there is a gap between the floor trap grating and gully pipe, the Works should provide a new UPVC grating adaptor to seal up the gap as shown in Annex E. In the case where there is an embedded discharge pipe connecting the gully but not properly installed, the embedded pipe shall be replaced with new UPVC grating adaptor as shown in Annex F. As and when instructed by SO Rep, the Works shall also provide a vertical grating with outlet(s), which is deem included in the Contract Rates. All fittings, elbow, waste pipes for connecting to existing basin / sink shall be reinstated by the Contractor. The affected area is to be reinstated with matching tiles.
Water seepage through defined area, such as through crack or porous concrete/mortar surrounding sanitary pipe, may be repaired by injecting an approved water-reactive polyurethane grout according to the procedure shown in Annex G. The water-reactive polyurethane grout shall be injected through injection ports embedded into the concrete/mortar. All stained areas must be cleaned up or painted. The Contractor shall always make available a team of competent workers to do the Works as and when instructed by the SO Rep.
Nano-Technology Repair Method
The Nano-Technology repair method is a non-destructive and no-hacking approach for the rectification of ceiling leak. The Contractor shall either engage experience workers to carry out such repair work or follow the material instructional guide provided by the supplier. The procedures for the method is as follow:
a) Replacement of existing pedestal pan and pan collar.
b) Replacement of existing floor trap and replace it with UPVC floor trap grating with long collar, if required.
c) Wash and clean tiles surface.
d) Patching up of small gaps and minor cracks on the tile’s joints.
e) Apply Nano solution on the surface of the wall (at least 2m high from floor surface) and floor tiles.
f) Refrain from using the toilet for at least 8 hours.
Painting to Lower Floor Unit Ceiling
Before commencement of any painting, the Contractor shall lay protective sheet to prevent paint dripping/staining on to the floor, any sanitary ware or other properties in the Site. Administrative charges shall be imposed on the Contractor for non-compliance.
The Contractor shall remove any existing paint peeling, debonded / delaminated skim coat or plastering on the affected ceiling. Where necessary, the ceiling shall be smoothened by grinding and all uneven surfaces flattened out with compatible pre-packed masonry plaster material. The ceiling surfaces to be painted shall be dry, brushed, sanded down, wiped with clean damp cloth and free from blemishes. The painted surface of the completed ceiling shall look smooth, even and flat without uneven marks or traces of existing paintwork.
The lower floor unit ceiling shall be painted with one coat of water-based sealer and two coats of emulsion paint at a period as instructed by the SO Rep after Works have been completed. The Contractor should properly survey/assess the necessary painting for the lower floor unit ceiling and ensure that the Works are properly and diligently carried out.
For Works affecting the whole balcony/service balcony, Contractor shall paint the complete balcony ceiling of the lower floor unit and/or abutting affected parts as directed by the SO Rep. For localised Works at the kitchen gully / balcony’s gully, Contractor shall paint the affected respective ceiling area at the lower floor unit in segmental area across the shorter length of the kitchen / balcony.
Unless approval is obtained from SO Rep, the Contractor shall not exclude painting from the Works for situations when flat owners and/or affected parties have indicated that painting are not required and SO Rep has been notified in writing. For cases when the Contractor had excluded painting from the Works without obtaining approval from the SO Rep, the Contractor shall carry out the required painting upon subsequent request/feedback by the flat owners.
Painting Of Pipes and Conduits
The Contractor shall clean and remove stains on pipes and conduits at the lower floor flat which is caused by the leak and apply two coats of enamel paint of matching colours to the affected area to the satisfaction of the SO Rep.
Painting Covered By Paint Warranty
If painting the affected areas are covered by Paint Warranty, the Contractor shall either:
(a) Engage the repairs & redecoration contractor/paint manufacturer who have given the warranty to repaint the areas affected so as not to invalidate the warranty; or
(b) Reinstate with a colour which matches the surrounding areas and provide the warranty for the same duration as provided by the repairs & redecoration contractor/paint manufacturer.
RECTIFICATION OF SANITARY OPENING
The Contractor may be required to remove and reinstate the in-filled concrete/mortar in the slab at those locations previously designated as sanitary opening. The rectification work shall be carried out according to the following procedure:
(a) Measure the locations of all the filled-up openings on the ceiling of the lower unit and mark out their respective positions on the floor surface of the upper unit.
(b) Erect the necessary props to the lower unit as shown in Annex I. Nylon pocket shall be attached to the props for collecting debris during hacking.
(c) Remove the tiles and in-filled concrete from the filled-up opening by portable electric breaker.
(d) Enlarge the opening to expose the slab bottom reinforcement. The side surface of the enlarged opening shall be tapered such that the opening is bigger at the top as shown in Annex I.
(e) Clean the surface to be free of dust and unsound particles.
(f) Erect the formwork adequate supported with props.
(g) Lay 3 pieces of 10mm galvanised steel bars at both directions within the opening. The bars shall lapped and tied with wire to the existing exposed bars.
(h) Apply bonding agent on the 4 sides of the opening and fill up the opening with approved non-shrink cementitious mortar.
(i) Formwork and props shall be removed after the mortar has been cured for 24 hours.
(j) Repaint the affected ceiling to match with the existing colour.
The Contractor shall comply to the technical specifications and laying method of tiles in accordance with the Standard Specifications, Section 19 and Section 20. The tiles used shall match the dimension, colour tone and evenness of the existing tiles as approved by the SO Rep.
At least eight (8) numbers of sample tiles, comprises at least two (2) numbers with darker colour, shall be provided to the flat owners and/or affected parties for selection. The Contractor shall also provide more numbers of sample tiles upon instruction by the SO Rep. All sample tiles shall be approved by the SO Rep and shall be reviewed periodically.
The Contractor shall execute the Works and not impose any additional charges on the flat owner and/or affected parties for the following situations as these costs are deemed to be included in the Contract Rates:
a) Supply and lay tiles that are of different types and sizes from the approved list of materials or
b) Laying of the tiles (not limited to ceramic tiles or homogeneous tiles only) provided by the flat owner and or affected parties.
The type of tiles provided by the Contractor shall be subjected to the approval of the SO Rep. The SO Rep shall have the absolute prerogative to select the type of tiles from the list of approved ceramic tiles and no adjustment to the Contract Rate shall be made.
Notwithstanding any approval by the SO Rep, the Contractor shall ensure that all such tiles comply with the requirements as specified in the Standard Specifications.
Treatment of Surfaces to Receive Cement/Sand Rendering
The existing tiles and mortar bed shall be fully removed using approved tools to the bare concrete, blockwall or brickwall. If the surface is smooth, keying may be produced by the application of a ‘spatterdash’ coating or bonding agent.
Pre-Packed Screed and Pre-Packed Waterproof Screed
Approved prepacked waterproof screed shall be used for the floor in the kitchen, toilet, bathroom / water closet (WC). For those floor areas, which do not require waterproofing, approved prepacked screed shall be used.
Movement joints shall extend through the tiling and its beddings and shall be a minimum of 6mm wide. The movement joints shall be provided at approximately 4.5m apart over the tiling area, upon the instruction by the SO Rep.
The joints to seal shall be capable of accommodating the anticipated amount of movement without loss of adhesion to the sides of the joints and be able to withstand the normal service conditions. The sealant shall only be applied until the joint spaces are thoroughly clean and dry.
Use of Proprietary Tile Adhesive
Where existing tiles are laid with thin-set tile adhesive, the defective tiles shall be reinstated with tile adhesive. Within 14 calendar days from the date of Letter of Acceptance issued to the Contractor, the Contractor shall submit the proposed material to the SO Rep for approval.
The tile adhesive shall be of a two-part system. No water shall be added to the mixture at site.
Installation of Glazed Wall Tiles
The wall tiles shall be white-or-pattern-colour glazed wall tiles and of size matching the existing or unless otherwise specified by SO Rep. If the repair of tile within the flat is only partially, the selected wall tiles must match or close to the existing tiles.
The pattern colour glazed tiles shall conform to the requirements of the latest version of SS57 (including colour, flatness requirements) and to be tested by recognized and approved accredited laboratory.
(a) Prepacked Mortar Bedding for Wall Tiles
The wall surface to receive new rendering shall be cleaned and free of sand, loose mortar, laitance or other substances that destroy the natural key / bond for rendering. Care shall be taken to ensure that surfaces dampened do not dry out before the rendering is applied.
Pre-packed mortar mix shall be mechanically mixed with the right amount of water in accordance with the manufacturer’s instruction.
Rendering up to a maximum of 10mm may be applied as a single coat. The following coat shall be applied after the first coat is allowed to harden and dry out.
The rendering shall be allowed to cure for one day before the laying of tiles begins. The rendering shall be true, free of hollow-sounding areas and firmly bonded to the background.
(b) Laying of Wall Tiles
The glazed wall tiles shall be unpacked and soaked thoroughly in potable PUB water for at least 12 hours and subsequently stacked verticals to allow excess water to drain off prior to laying. Spread the bedding mortar (pre-packed mortar) uniformly over the tile back with thickness of about 2mm after filling the depression on tile back. Place each tile and tap it firmly into position to ensure that each tile makes contact over its whole area. Adjust the position of any tile within 5 minute of fixing.
Clean off mortar splashes from the face of tiles 2 hours after bedding is complete, taking care not to disturb the tiles.
Laying of Floor Tiles
The Contractor shall strictly comply with the manufacturer’s recommended installation procedures and/or the following work method:
(a) Surface Conditions
The floor tiles are to be laid on top of the existing floor screed. The Contractor shall ensure that the condition of the floor screed is suitable to receive the adhesive and the tiles. Any defective floor surface such as hollow screed, potholes etc, shall be rectified before the floor tiles may be laid. The method of rectification shall be approved by the SO Rep before Works may commence.
(b) Surface Preparation
The surface of the floor screed to receive the tile adhesive shall be clean and free of dirt, oil, grease, concrete sealers, paints, coatings and other impurities prior to laying of materials. All loose particles, paints and other debris must be removed.
The 2 components-tile adhesive shall be mechanically mixed with appropriate mixing ratio strictly according to the manufacturer’s instruction. The mixture to be used shall not exceed the pot life specified by the manufacturer.
(d) Application and Laying
The tile adhesive shall be applied onto the surface of floor screed then notch- trowelled to a finished thickness not exceeding manufacturer’s recommendation. The area of application shall not exceed 1.0m2 each time per worker. The tile adhesive shall also be spread uniformly over the back of each tile, taking care to fill deep keys and all remaining depressions. The tile shall then be placed into position within the specified open time and be tapped firmly into position to ensure that each tile is made fully contact over its whole area.
The tile joints are to be pointed with approved proprietary coloured tile grout after their final set.
Upon completion of all tiling and pointing works, all the excessive adhesive and other blemishes shall be removed from exposed surfaces using neutral cleaner recommended by the manufacturer.
(f) Mortar Bed
The floor surface to receive new screed shall be cleaned and free of sand, loose mortar, laitance or other substances that will destroy the natural key/bond for rendering. Care shall be taken to ensure that surfaces dampened do not dry out before the screed is applied.
Pre-packed waterproof screed or pre-packed screed as instructed by SO Rep shall be mechanically mixed with the right amount of water in accordance with the manufacturer’s instruction. The overall thickness of the prepacked mortar screed including the thickness of tiles shall be about 40mm.
The screed/mortar shall be laid to fall evenly towards water outlets. Unless otherwise specified by the SO Rep, the falls in the Kitchen and WC shall be 20mm and 25mm respectively. The screed shall be allowed to cure for one (1) day before the laying of tiles.
(g) Standard of the Floor Tiles
Generally, the floor tiles shall be working size for bathroom/WC unless otherwise specified by the SO Rep. The ceramic floor tiles used are to comply with Clause 19.9 of the Standard Specifications.
For area where glazed porcelain floor tiles is specified, it shall comply with Clause 19.5 of the Standard Specifications. Where the size of glazed porcelain floor tiles issued in the Works Instruction is of other sizes, all sub clauses under the heading “glazed porcelain floor tiles” shall be applicable as specified in the Standard Specifications.
The method of installation for sanitary items shall be based on the Standard Specifications, Section 36, 37, 38, and 41.
Low Capacity Squatting WC Pans
Where installation of squatting w.c. pans, it shall be of vitreous china complying with SS 379, the “Singapore Standard For WC Pans For Use With Low Capacity Flushing Cisterns” and with `P’ or `S’ traps with cleaning eye. The cleaning eye at ground floor shall be UPVC screw cap to SS 213.
Each pan shall be complete with approved high level plastic flushing cistern to SS574 “Dual flush low capacity water closet (WC) up to 4.5/3.0 litres capacity and UPVC flush pipe of minimum 32mm diameter.
Flush pipes shall be held at mid height by holderbat securely fixed to wall. Overflow from cisterns shall be drained within building.
Carry out concrete infill and floor finishes around pans. Provide foot treads where there is no floor tile finish.
Where the existing squat pan protrudes below the reinforced concrete floor, the Contractor shall hack the pan and floor to remove the pan and seal up the opening with high strength grout. Bonding agent shall be applied to the concrete interface between the old and new concrete. Provide new low capacity squatting WC pans complete with cistern, discharge pipes, UPVC pipe, fitting or low capacity WC suite.
Low Capacity WC Flushing Cisterns
All flushing cistern must comply with the SS 574 “Dual flush low capacity water closet (WC) up to 4.5/3.0 litres capacity”.
Flushing cisterns shall be approved high level flushing cistern or other approved in which metal pull chain will release not more than 4.5 litres of water.
Fixing Low And High Level Cisterns To Wall
New support brackets and spacer shall be provided for back fixing of the cistern. All stainless steel support brackets used for installing cisterns (high or low level type) shall be of suitable design and comply with SS 574. The stainless steel shall be of grade 304.
The spacer shall be of non-corrosive material and shall firmly adhere to the back of the cistern shell and the wall. The support brackets shall be installed at the base of the cistern.
Fix flush pipe support bracket to the wall for every 600mm run of pipe. When installed, the cistern shall be free from any movement while the operating lever arm is pulled down for flushing operation.
PLANT AND EQUIPMENT
The Contractor shall provide all required protective sheet with adequate thickness for the proper protection and execution of the Works. Mechanical mixer shall be used for mixing cement-sand mortar on site.
The Contractor shall provide and maintain all scaffolding required for the Works.
The scaffolding shall be erected in accordance with the relevant By-Laws and to the satisfaction of the Inspectorate of Factories. Scaffolding shall only be removed when directed by the SO Rep.
PROPPING AND STRUTTING
The Contractor shall provide and maintain during the execution of the Works all necessary propping, strutting and other supports to support adequately the structural members to be repaired and any adjacent structures, and shall take all necessary precautions or adopt such other approved measures as may be necessary to prevent damage to the unaffected parts of the structure. The Contractor shall note and take all responsibility for the satisfactory performance of the propping and all other supports for the purpose for which they are erected. In the event of any damage occurring due to the inefficiency of the supports, all the damage resulting thereof shall be made good by the Contractor at his own expenses. Any approval given by the SO Rep in respect of the propping and strutting shall not relieve the Contractor of his responsibility in the safety of the structure under repair.
Timber plank of minimum size 400mm x 200mm x 50mm must be permanently fixed to the top end of each vertical prop to distribute the load of the floor slab. In addition, timber joists of minimum cross-section size 50mm x 75mm must be used to brace each hacked area which is larger than 1.5m2.
These timber joists and planks shall be available on site before the commencement of hacking works. These timber joists and planks shall be removed from the Site at the end of each working day.
The Contractor shall also provide timber plywood at the upper unit over the areas to be repaired. The timber plywood shall act as a “bridging” over the hacked area and shall be framed at the underside all along its perimeter.
All parts disturbed or damaged during the execution of the Works shall be repaired or replaced to match existing. All floors shall be thoroughly washed, marks of paint work shall be removed and the works minor touched up.
All debris and Contractor’s tools, materials and equipment shall be removed on completion of the Works and the Site shall be clean and tidy to the satisfaction of the SO Rep.
GRINDING OF CONCRETE SURFACE
Where grinding of concrete surface is required, the Contractor shall use vacuum blasting machine for the grinding to minimise the dust generated. Other alternative methods proposed by the Contractor shall be approved by SO Rep.
The Contractor shall adopt the relevant safety measures when carrying out the Works. The Contractor shall provide and maintain safety nets to trap debris from falling to the ground. Those affected areas in the vicinity of the ground floor shall be strategically barricaded, complying to the approval of the HDB’s Safety Unit. The Contractor shall also provide overhead shelter at lift lobby and letter boxes areas while the Works are in progress. The Contractor is deemed to have allowed for all costs of the safety provisions in compliance with the Workplace Safety and Health Act including the Regulations and any other subsequent changes to the Act and/or Regulations.
The Contractor shall provide suspended mechanical cradles at any time for carrying out Works at those areas not accessible by metal scaffolds. These mechanical cradles shall be in good and serviceable condition and shall not be more than three years old. The Contractor shall provide all necessary submission of structural drawings and calculations by their Professional Engineers to the HDB’s Safety Unit for approval. The cost for the hiring of mechanical suspended cradles shall be paid by the SO Rep in accordance to the Schedule of Rates. The Contractor shall not be paid for additional costs that may arise from amendments to the Regulations and changes in the requirements from Ministry of Labour and HDB.
FACILITIES FOR SUPERVISION
Contractor shall provide all facilities, instruments, proper access necessary for inspecting the progress of the Works as and when directed by SO Rep at no extra cost to HDB.
TAKING OF PHOTOGRAPHS AND VIDEOS
The Contractor shall take reasonably sharp photograph and/or video before, during, and completion of the Works, and produce these evidence as and when required by SO Rep. The photograph/video shall be taken with location tags enabled mode and no editing of this geographical information is allowed. The image resolution shall be at least 1024 by 768 pixel and video at least HD 720p.
For convenience of viewing by SO Rep, the photograph/video shall be uploaded instantly to “Cloud” subscription service, such as Google Drive, OneDrive or equivalent. These evidence shall be kept in folders organised by the road name, block number, and unit number, and the web link to be shared to the SO Rep.
The photograph/video shall to be made available throughout the Contract Term, Defect Liability Period, or the extension of Contract Term, whichever is later.
The cost and all other related charges for this provision shall be fully borne by the Contractor.
The Contractor shall engage a licensed plumber to supervise and to be fully responsible for sanitary and water installations so as to comply with the current codes of practice, Bye-laws, and requirements of the relevant authorities. The licensed plumber shall liaise with the relevant authorities on all matters relating to the installations.
The Contractor shall engage a licensed electrician to supervise and to be fully responsible for electrical installations so as to comply with the current codes of practice, Bye-laws, and requirements of the relevant authorities, where necessary. The licensed electrician shall liaise with the relevant authorities on all matters relating to the installations, where necessary.
As and when requested by the SO Rep, the Contractor shall carry out water test for a minimum period of 4 hours and at a height of minimum 25mm after the waterproof screed has been laid and cured in the units at no additional cost. The water test shall be conducted with the inflation ball and water tightness must be ensured.
PORTABLE BATHROOM/TOILET INSIDE FLAT
The Contractor shall provide, install and maintain a portable bathroom/toilet, complete with water supply and equipped with shower and tap points, inside the flat during the execution of the Works. The portable bathroom/toilet may be installed in the kitchen or other locations within the flat identified by the SO Rep and shall be made functional at all times including during the execution of the Works inside the flat. The portable bathroom/toilet shall be connected to the existing main soil stack for the discharge of waste.
Where the SO Rep is of the opinion that the portable bathroom/toilet cannot be made functional during the working hours without severely obstructing the Works, the Contractor shall be required to make the portable bathroom/toilet functional at the end of each working day.
Unless otherwise approved by the SO Rep, the portable bathroom/toilet shall remain inside the flat for the duration of the Works inside the existing bathroom/toilet. Upon completion of the Works, the Contractor shall wash and clean the portable bathroom/toilet thoroughly before dismantling it and reassembling it in another flat.
In the event that the portable bathroom/toilet cannot be placed inside the flat without, in the opinion of the SO Rep, severely obstructing the flat owner’s and/or affected parties’ daily routine, the Contractor shall render the existing bathroom/toilet undergoing repairs suitable for use including
the provision of a temporary PVC or other approved pedestal pan. The temporary pedestal pan shall be connected to the existing or newly installed main soil stack for the discharge of waste at the end of each working day. The Works completed during the day shall be properly protected against possible damage due to usage of the existing bathroom/toilet. The Contractor shall be responsible for the rectification of all damages to the Works resulting from the existing bathroom/toilet undergoing repair being subject to usage.
REPAIR PROCEDURES TO SPALLING CONCRETE (PATCH REPAIR METHOD)
(a) For widespread spalling concrete and/or spalling concrete on structural member, the Superintending Officer’s Representative shall consult the engineer whether there is a need to prop the defective structural member and the adjacent structural members prior to the commencement of repair works. The propping method and materials shall be approved by Superintending Officer’s Representative.
(b) Remove the defective concrete (or spalling concrete) area with hammer and chisel or other approved pneumatic/electric tool (impact energy not greater than 4Nm) to a depth not exceeding 25 mm unless directed otherwise by the Superintending Officer’s representative.
(c) Remove rust from rebar using wire brush or other approved means. If the cross-sectional area of rebar is reduced by more than 15%, additional rebar with proper lapping must be added.
(d) All sagged rebars shall be bent upward and tied up at every 250 mm interval in order to provide adequate concrete cover.
(e) Prime all exposed rebars thoroughly with approved rust inhibitor.
(f) Apply the exposed rebars and concrete surface with 1 coat of approved ‘bonding aid’ to ensure good adhesion with the repair material.
(g) Apply the repair mortar (approved polymer modified cementitious mortar or epoxy mortar) in layer of no more than 20mm each and allow 4 hours between layers. The ‘bonding aid’ is required between successive layers.
(h) Apply an approved protective coating to the patched surface area as specified by the Superintending Officer’s Representative.
(i) Paint the patched surface to match the adjacent surface.