The conclusions I have come to from my report are that without the fundamentals of the design and build stages that construction of buildings could encounter many problems. Some of these can be altered to suit but some could be detrimental on getting building approval and could also become very costly endeavour if not. There are many considerations to take in affect within the construction industry. It is not just the build concerned but the environmental impact issues and the people it effects. The construction of this small project has many points to consider before build can commence as well as during construction phase. I have only covered a few points in the early stages of construction but have liaised with architects, local authorities and suppliers of materials who all have some input regarding the build of this building.
I have been instructed by the club chairman of Bogsworth sports and leisure club to look into the possibility of building a new club house on land which the club have been offered first offer on price. I will be arranging a site investigation to see if the proposed land is viable to build on. From these results I will propose a suitable form of construction which I will outlay all the stages of substructure and my reasons why. The report will be in the way of text and diagram information illustrating professional responses and knowledge of the construction industry.
Before any design in building can be considered a site investigation has to be undertaken. This will provide information about the proposed site and land adjacent. The site investigation is in three stages. Desk Study, Walk-over survey and Ground Investigation (Physical exploration and inspection).The site investigation is a requirement of approved document C (site preparation and resistance to contaminants and moisture).
The desk study is the first stage of a site investigation; it will look into the history, geology and topographical information of the proposed site. Historical and ordnance survey maps will give insight into what the land was used previously and also future proposals. It will detail boundaries and any potential hazards such as rights of way, risks of flooding, quarry and mining issues, landfill where harmful contaminants could lay, vegetation and utility services. Speaking to the local authority, will give a more in depth insight into what the land has previously been used for and any future proposals concerning the land and adjacent land. They will be able to provide information on where existing and past utilities are situated which will help in the design and construction stage. It will give the history of previous use and of any contamination issues which have come to light in the past. Speaking to local residents may also prove beneficial because they may know of any flooding or quarry mining issues that are known. Informing the local community of your proposals would be beneficial to see if any possible objections to planning may arise.
A walk-over survey will investigate in more detail on what will be shown from the desk study. The surveyor or engineer will have the opportunity to make more detailed drawings of the land and surrounding area, such as adjacent buildings, vegetation and groundwater detail. As well as drawings, photographs will be taken to be used as information in possible design and highlighting potential hazards. The check list produced from the desk study will be observed throughout the walk-over survey to see if anything has been missed and additions will be noted for further investigation. If further investigation is needed then this will be given to specialist contractor at ground investigation stage.
The ground investigation will be trial pits being dug and bore holes drilled at different points of the concerned land. The usual procedure would be 12 trial pit holes using a hand augur to depths of 2, 4 and 6 metres. This will ascertain nature, thickness and stratum depth of subsoil, groundwater levels, and contaminants and any potential hazards. Samples will be 5 for moisture content, 3 for organic matter, 2 for particle size and 2 for California bearing. These will be sent to a laboratory for analysis and results made returned. The results will determine if a build can proceed or any design changes will have to be implicated.
All soil and water samples will be prepared in accordance of:
BS5930 1999 Code of practice for site investigation
BS1377 1990 Part one
BS10175 2001 Investigation of potentially contaminated sites – Code of Practice
Diagram 1.0 Shows at what depths of when subsoil’s and groundwater levels were found using
A hand augur.
The proposal for substructure works will be outlined in accordance with BS 8103-1 1995 Structural design of low-rise buildings. Code of practice for stability, site investigation and ground floor slabs for housing .http://www.ciob.org.uk/bsstandards/substructure. It has come to notice from the site investigation report that several small ponds were filled in over 25 years ago. The land has shown to have now settled but is still showing evidence of groundwater possibilities. For this reason I am proposing specialist contractors to come and dewater the proposed site before any construction begins. Once this is in place I propose using end bearing piles to transmit the loads of the structured build to good bearing ground. This will be in accordance with BS EN 996: 1995 + A3 2009 Piling equipment. Safety requirements. http://www.ciob.org.uk/bsstandards/piling.
Temporary Water Control
The Well Point System is my choice of method for temporary ground water control. The system uses the pressure of water to drive a well point and suction pipe into the ground to maximum depth of 5 metres. The well point contains a valve allowing jetted water to remove soil as it is lowered to its required depth. Once this is reached it is then connected to the suction pump where the jetting valve closes, allowing the groundwater to be drawn into the riser pipe through the perforated section of the well point. Here it is then pumped through a filter incorporated in the suction pump which purifies the contaminated water. This can then be pumped away into the service drain or away from site. At the same time it is lowering the water table and providing a dry working level to begin works.
Diagram 1.1 Well Point System in operation
Diagram 1.2 Well Point system dewatering
End Bearing Piles
End Bearing Piles will be used in the formation of this construction. They are used where weak subsoil such as filled ground above firm strata has been shown. The pile will transmit the imposed load to the firm strata. They will be done by a specialist contractor which may seem costly but overall it will actually save on cost by using less concrete in the ground beam construction. The End Bearing Piles will be percussion bored into the ground to the required depth removing the subsoil. In situ concrete will be poured into the exposed hole followed by a reinforced cage pushed through the concrete. When these are set they will be cropped by plant machinery to the required height for pile caps to be formed. The position of the piles will be determined by the site engineer. Voids between the end bearing piles will be filled with crushed hard-core vibrated to make compact. These will be in compliance and accordance of: Building Regulations A – Structure & C – Moisture
BS 8604 Code of Practice for Foundations
BS8110-1 Structural use of concrete code of practice for design and construction
End bearing piles
Ground Beam Floor Slab
The ground beam floor slab will be incorporated with the cropped piles to form the required support for the ground floor of the building and external brick and block walls. Trenches will be dug to the required depth normally 750mm exposing top of the piles and 450mm in width. See diagram 1.4. They will then be filled with compacted hardcore to a depth of 425mm with a 75mm sand binding on top of this. The DPM will be laid on this with 50mm insulation on top of the DPM in place for the concrete slab to be poured, with a final screed of 50mm in thickness to complete.
Preparation of concrete slab
Once the base for the concrete slab has been laid it is now time for the reinforcement to be introduced, this will be in the way of steel mesh 2400mm x 1800mm being placed on top of visqueen with spacers in between. (The spacers are normally steel caging but concrete blocks can be used). The steel mesh will be cut to size where needed and kept in place using tie wire, ensuring the spacers are also tied to the steel in case the concrete pushes them over. Once the steel mesh is secured that is the reinforcement for the base complete. Now it is the time to for the formwork to be put in place so the concrete formation is held in place. The formwork for this proposed construction will be in the way of using on site built timber shutters. There are other means of putting formwork in place; using steel pans or factory made mechano shutters but timber will be sufficient for this type of construction see diagram 1.5.
The formwork will be put around the steel keeping a 50mm space between the steel and formwork. Reason for this is so no steel is protruding when the concrete has been poured. In the likelihood of this happening it could be possible for the work to be condemned by the building inspector. The formwork will be kept in place using strutting and braces where needed. To stop any possibilities of any bursting when concrete being poured the strutting will run from the formwork to the trench embankments. Once the concrete is poured to a depth of 150mm it will be floated off with a brushed finish to incorporate the 50mm screed to bond to it. The screed will be of a dry mix of sand and cement, which will complete the ground beam slab.