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This Construction Method Statement describes the development of six houses in three identical semi-detached blocks on a plot of land. The document will suffice for the majority of works undertaken during the construction but will require alterations or additions for certain projects. This method statement is a qualified assessment based on current information and is subject to refinement as the project evolves. This method statement is prepared to discuss about all the construction process and operations and also emphasize on the health, safety and environmental concerns.
Access and Material Distribution
Constant flow of transport is needed during the construction period. Small access roads and driveways together with temporary roads are constructed to define site circulation routes and provide a suitable surface for plant movement (Chudley & Greeno, 2008, p.118). A small access road is set up nearby the storage area of the site to transport materials that are required within a short space of time. A forklift will be used for material offloading and distribution around the site. The location of the access road shows in the Figure 1 site layout plan. Moreover, the road will be subjected to light and heavy day to day traffic such as concrete delivery, steel delivery lorries, brick and block delivery lorries and delivery vehicles generally. All the deliveries will be fitted into a delivery schedule system which is controlled by site personnel under guidance of Construction Manager. (Griffith & Watson, 2004, p.392) Materials are closely phased and delivered when assembled which to achieve just-in-time management in this project. Materials that are transported with heavy goods vehicles (HGVs) are expected to take place at night and that certain works may have to be undertaken during this period so that it does not cause disruption to traffic flows, especially at peak times.
Storage on site is erected to store materials, tools and equipments, spare parts for mechanical plant, and manufactured goods for incorporation in the work. (Griffith & Watson, 2004, p.188) The distance between storage and activity areas keeps short to reduce transportation needs in terms of time. Timber and steel reinforcement will be stored in a dry safe place and special store for fuel oils needed by the requirement of legislation. (Griffith & Watson, 2004, p.189)
2.3 Site Office
A temporary site office will be provided on the site for management purposes and paperwork. These offices will be housed in modular portable units. The size of site office will be calculated based on an example below:
Office for site agent and assistant plus an allowance for 3 visitors. Assume an internal average height of 2.400. Allow 3.7m2 minimum per person and 11.5m3 minimum per person.
Minimum area = 5 x 3.7 = 18.5m2
Minimum volume = 5x 11.5 = 57.5m3
Assume office width of 3.000 then minimum length required is
= 57.5/ (3x2.4) = 57.5/7.2 = 7.986 say 8.000
Area check 3x8 = 24m2 which is > 18.5m2; satisfactory (Chudley & Greeno, 2008, p.94)
2.4 General Site Facilities
General site facilities such as toilets, changing facilities, canteen, as well as shelter from inclement weather will be provided on site. Adequate heating, lighting and ventilation are required in all toilet, washing, changing, and accommodation. The requirements of each facilities are specified the Health and Safety Executive (HSE) legislation (Griffith & Watson, 2004, p.192). The location of all the facilities must be close together for easy access. The site accommodation will be located in the north corner of the site so to suit site access strategy. A row of single storey accommodation will be needed in the project. All the facilities buildings build in portable.
2.5 Site Enclosure - Fencing and Hoarding
A minimum height of 2.4m hoarding and fencing will be erected around the perimeter of the site for protection (Griffith & Howarth, 2001, p.252). Safety measures outlined by the Albert Building Code (ABC) must be followed. An external signposting will be installed around the hoarding to enable the site to be more visible. Caution signs will also be displayed on fences and gates so that people will be aware when passing through the site. There will be a principle gate to the site along with pedestrian gates for access.
2.6 Safety and Security
For both security and safety reasons, site-bases security presence will be provided during normal working hours with a visiting patrol covering nights and weekends to protect against theft and vandals of storage. Site-based security presence with a full 24 hours will be in place during the later stages of the construction works and fit out prior to occupation (Griffith & Watson, 2004, p.391). All entry points will be clearly signed with appropriate warning notice. Flood lightings with 500 watts in 7.50m high are installed as a measure of night security. (Chudley & Greeno, 2008, p.91)
Main Construction Work
Concrete strip foundation will be used as the foundation of the houses. Foundation works include excavating, earthwork support, concreting and bricklaying of the strip foundation. Trenches are excavated under the line of the walls and the soil at the bottom of the trenches is compacted. Rough sawn timber as strutting will be temporary support for the sides of excavation for strip foundation. At least 150mm of concrete is placed at the foot of the trench with a concrete pump and brick walls are then built up to the damp proof course (DPC) which will be at least 150mm above ground level. The DPC is bedded on a layer of mortar on each leaf of brick or block cavity foundation wall. (Osbourn & Greeno, 1997, p.199) The depth of the strip foundation of 1m - 1.2m is adequate to ensure the soil acting as the natural foundation cannot be affected by the weather and stake will be used to determine depth of concrete foundation (Osbourn & Greeno, 1997, p.181 &186). The strip foundation made of a continuous strip of concrete with 1:3:6 mix. Hardcore will be compacted using a vibrating plate or roller and the top of the hardcore is kept below the substructure block work so that the slab can be cast inside the walls. Concrete is protected with a sheet of hessian or sand in cold weather and sheet of polythene in hot weather. (Marshall& Worthing, 2000, p.57) The provision of damp proof membrane (DPM) for the entire area on top is between the over site concrete slab and it will be done on a bed of sand or ash of 12mm thickness.
3.2.1 External Wall
Cavity wall will be used in this project as it has good thermal insulation and weather resistance properties. Cement-lime mortar mixes is used to ensure adequate bond of ties to wall. An adequate size of vertical spacing will be required for door and windows opening.
In Mitchell's Intro to Building (Osbourn & Greeno, 1997, p.207) states that, "As the work progress beyond a height where it is unreasonable for the bricklayer to lift materials from ground level, it will be necessary to erect scaffolding to support raised working platform."
The scaffolding with aluminum alloy which connected by special fitting or couplings will be used to lay the upper floor wall.
3.2.3 Doors and Windows
Temporary props will be erected until lintel construction has been complete. To connect the opening frames with the wall, rigid-angled galvanized mild steel lugs screwed to their side edges as the work proceeds. (Osbourn & Greeno, 1997, p.203) DPC will be bedded when the work is carried out.
3.2.4 Internal Wall
Work sequence will be similar to external wall but the internal wall is in single leaf. The partition wall will be positioned and used to separate spaces within the building into rooms. Insulated plasterboard will be installed through the wall to gain thermal for the building. (EDP Energy, 2010)
Pitch roof which erected by timber trussed rafters space about 600mm at close centres to provide direct support for roof cladding and ceiling. (Osbourn & Greeno, 1997, p.221) Install the ridge board on 2 end posts with temporary bracing and set it straight and level. Each rafters is nailed to the wall-plate which ready placed on a mortar bed on top of cavity block wall. (Osbourn & Greeno, 1997, p.221) Prefabricated ladder fixed to the end trussed rafter. Fascia board fixed to the feet of rafter and barge board to the outer face of gable ladder. (Marshall& Worthing, 2006 p.94) Install collar ties, purlin and bracing as needed for the rafters and ridge to prevent sagging over time. Timber trusses with bracing are manufactured off-site. Clay tiles will be laid in continuously on the timber battens on sarking felt with 45 degree sloping of pitched roof.
3.3.1 Internal Wall Finishes
Plaster board will be applied to internal wall as finishes with wet plaster method. Half-hour fire resistance will be provided when 5mm coat of wet plaster and 9.5mm thickness wet plaster applied on both sides of partition wall. A gap which is used to provide additional air passage is left between the back of plaster board and the face of the wall. Then the gap will be connected to the cavity to the internal environment to allow air leakage. (Emmitt & Gorse, 2005, p.535) Emulsion paint with Water Based Paints Timber will be painted through the wall using the roller method. (Chudley & Greeno, 2008, p.669)Skirting board with 19mm thickness will be nailed to the concrete fixing blocks at the base of walls after plastering is completed. (Emmitt & Gorse, 2005, p.548-549)
3.3.2 Floor Finishes
Skim coats with mix of cement and water applied with a steel float to make smooth finish on screed to allow carpet laid on it as floor finishes. Tackless strip placed around the entire perimeter rooms and shoot masonry screws into the strip and cut the strip by tin snip. Underlayment will be pour to hold the carpet padding. (Beach,1999-2010)
3.3.3 Ceiling Finishes
Plasterboard ceiling made with a core of gypsum sandwiched between face sheets of strong durable paper with 2.4 x 1.2 x 9.5 mm thick at centres and it fixed to joist by nailing. Then, 5mm single coat board finish plaster over bonding grade undercoat. (Chudley & Greeno, 2008, p.664)
3.4 Existing Services
Existing services drawings will be obtained for the site area, which are applicable to the complete development and must be referred to at all times. Prior to any mechanical excavation commencing, each suspect area will be hand dug to confirm the depth and location of any service and clearly marked on the surface. Extreme care will be taken when planning to work in these vicinities i.e. double check with CAT and Genny and follow above procedures. (Marriott 2009)
4.0 Health and Safety
4.1 Significant Hazard
Moving plant or vehicles
Operative have to be trained and competent to operate the plant or equipment. They should understand the emergency and evacuation procedures. ( Prifysgol Bangor University, 2001-2010)
Isolating workers or pedestrians from the moving plant. (Department of Labour, 2007)
Maintenance and servicing of plant. (Department of Labour, 2007)
Operator must follow all the directions in the hazard management. (Department of Labour, 2007)
Falls of materials
Materials fall as bricks or steel through hole or gap will cause injury people working below.
Keeping working platforms clear of loose materials.
Provide a way of preventing materials or other objects rolling, or being kicked, off the edges of platforms by with toe boards, solid barriers, brick guards etc at open edges. ( Prifysgol Bangor University, 2001-2010)
Safe working platform
Free of openings and traps through which people's feet could get caught, causing them to trip, fall or be injured. ( Prifysgol Bangor University, 2001-2010)
Risk of fire may be occurred.
Good housekeeping with keeping the workplace cleans all the time. ( Prifysgol Bangor University, 2001-2010)
Work at height
Accident as falling from height during laying brick or block at height level and also cladding and roofing.
Temporary scaffolding will be used during the height risk works.
Assess weather condition before working at high take place.
4.2 Personal Protective Equipment
Personal Protective Equipment (PPE) is an effective method of controlling occupational hazard. Operatives have to wear safety helmet at all times on site. Besides, suitable safety footwear such as steel-toe-capped boots will be worn by all company personnel. Casual shoes and trainers will not be permitted. All personnel are required to wear high visibility jacket or clothing at all times. This clothing must be suitable for the working environment and prevailing weather conditions. Eye goggles, hearing and respiratory protection and protective clothing will be made available for use where required and according to on site conditions. Furthermore, gloves have to be worn all the time can trap hazardous chemical against skin.
5.0 Potential Environment Impact
A review of the potential environment impacts associated with construction works are being considered. Below is a table of the different environment Impacts:
Run-off from plant or vehicle washing.
Material spill to drains and watercourses.
Discharge of contaminated water.
Disturbing contaminated ground.
Wind blow contamination.
Existing contamination of site.
Spillage and leakage of hazardous substances.
Noise and vibration contamination
Increased road noise levels from vehicles.
Particular methods of construction or use of heavy plant, equipment and haulage.
Traffic congestion caused by site.
Increased vehicle movements mainly consisting of heavy goods vehicles.
Transfer materials from vehicles into public road as main road.
Disruption from abnormal or hazardous loads.
Exhaust emissions cause air pollution.
Plant and wildlife contamination
Habitat disruption or destruction
Disruption to wildlife activity
Changes to natural environments ( noise, dust, light )
Disruption to food or water sources.
Disruption or destruction of natural features
Disruption by temporary works like access road
Table 1: Potential Environment Impact