After several design team meetings between client and contractor, a new-build scheme has been arranged and agreed to go ahead. The design proposal is a 4-storey commercial building that is situated within existing 'live' buildings. Subsequently, the southeast and northeast sides of the proposed building are to become party walls. This factor has the potential to create possible hitches within the construction phase of the project with regards to time constraints and cost.
The challenge is to successfully plan and execute a site layout strategy that is capable of maximum production with minimal complications. In order to carry this out, all parties involved must advise and communicate efficiently, whilst regularly informing one another of changes to the scheme.
From the outset, details of site layout must be thoroughly analysed in order to gather accurate information regarding the needs for the construction phase works. This includes; cost, materials, plant, security, storage, temporary accommodation and SWMP (Site Waste Management Proposal). All of this information is cost calculated and negotiated in what is known as the 'Pre-Contract Stage' of the project. At the pre-contract stage a contractor is already aware that he has a successful tender bid which in turn, increases the investment in time and planning of the project.
Furthermore, pre-construction agreements must be made by the client and contractor with the existing residents/tenants occupying near-by buildings of the proposed site. Access routes, shift patterns, noise pollution and a host of other obstacles must be established with the existing offices to minimize any possible confrontation during construction phase. In this particular case, the proposed 4-storey building is to have two party wall agreements. Consideration must be given to the southeast party wall, where a new basement could have the potential to pose minor issues. This could impact the existing buildings foundations and furthermore tanking of the wall will have to be granted due to the party wall agreement.
The single largest factor when planning site layout is temporary works. Illingworth, J.R (2000, pg. 35) defines temporary work as 'any temporary construction necessary to assist the execution of the permanent works and which will be removed from site on completion'. Producing a general scope of temporary works on site is advantageous, as it allows the contractor to work out what items he needs, how long he needs them for, and how much it will cost to the project.
Primarily, temporary site access must be established, ensuring public safety and also determining the most strategically suitable route for the chosen site. Safety is imperious when discussing preferred access routes. By looking at the proposed site, it is clear that there is not much room to work with, and extending the site boundary onto the public footpath should be considered. Although this interrupts public access, this strategy is safer for all around the site. By not extending the site, there is very little to work with, which could have implications on cabin locations and material storage. The proposed concept is to extend the site boundary onto the public footpath and a little beyond around the perimeter of the site. By doing this, a delivery/plant route has been created allowing more work space, easing site work congestion. "Safe Access and good visibility for plant and vehicles entering and leaving the site must be ensured. Where possible, pedestrians should be excluded from vehicle access ways. Trained banksmen should be used on busy highways near public footpaths and elsewhere if reversing is necessary." CITE IT RITE
Following on from this, plant must be negotiated. Weekly running costs as well as fixed charges must be calculated prior to plant delivery on-site. Thought must be given to the duration of plant use especially when thinking about cost. Availability of plant is also an important factor when planning site works. Positioning of the proposed static base tower crane is vital. By using a crane with a shortened jib, this will reduce the risk to surrounding buildings, transport and close-by public. Plant will heavily impact pre construction costs, so it is imperative plant duration has been thought out well; any over-hiring of plant could be classed as additional cost.
In terms of temporary on-site storage, straightforward access is principal. Not only does the storage have importance on the safekeeping of materials, but also of plant. Incorrect positioning of storage can result in a slower workforce which, ultimately, falls onto the programme, affecting several other tasks. Storage must be positioned so that it is accessible by crane. As mentioned by Tunstall, G (2006, pg.118), 'Location of stores and storage areas will be determined by the availability of space, the nature of the materials and any statutory requirements e.g. in relation to highly flammable materials or explosives. Consideration must be given to suitable off-loading areas and lifting equipment.'
Due to the restrictive nature of the site, planning the layout of the site accommodation will need to be well-thought. Determining the site accommodation will depend on the number of staff involved in the project. The space on site to store temporary cabins/storage etc. is very restrictive. If the area on site becomes too restrictive, the contractor may have no option but to rent accommodation adjacent to the site. Cooke & Williams (2009, p.279) comments that 'The space available on site may be at a premium and on restricted sites; consideration may be given to site accommodation on top of each other or locating the offices on a gantry over the pavement'.
One other main factor when executing a site layout strategy is an implementation of a site waste management system. Whether it is waste from excess material, temporary work, canteen waste or any of the many other causes, a SWMP (site waste management plan) must be implemented at tender stage. This will define the responsibilities amongst the design team, and what responsibilities they will have themselves. "When construction work commences onsite, it is the responsibility of the principal contractor to implement the SWMP. The principal contractor may have to develop and use SWMPs already created by other parties involved in the construction project. Also, information from trade contractors may be required, such as estimated waste arising's". CITE IT RITE
After thorough research in to the reasons behind a successful site set-up plan, the following summary has been produced along with supporting site set-up proposal drawings.
As shown in Appendix, Drawing 1.0, there will be an extension to the site boundary. To the south, the boundary extends over the pavement, to the east; the boundary will extend halfway on the road. The bounded road will act as the main delivery route, easing delivery and reducing driving time on site, minimizing risk. Because of this, a temporary traffic light system will be put in place.
Following on from this, temporary works related with plant use must be considered. Plants to be considered for a 4 storey new-build are;
Hydraulic backhoe excavator
Ready mixed concrete truck
Static based tower crane (with shortened Jib)
General purpose transport
The initial idea is to locate the Static based tower crane where the proposed lift shaft is to be installed. By doing this, the lift shaft can be built up around the crane.
On a site so restricted, using the JIT (Just in Time) method of construction would massively reduce the area on site given to storage, maximising work space. However if this method is not of preference, for the safekeeping of materials and storage, areas have been in shown in Drawing 1.1, Appendix 1 for adequate for the installation of temporary site cabins.
Similarly, for site accommodation & amenities (toilets, canteen, dry room), temporary cabins will be implemented. Because of the short distance between the site and contractors main office, site accommodation can be kept at a minimum, saving valuable floor area on site. Furthermore, these cabins will be stacked.