Structural Foundation and Various Types of Foundations - Assignment Example

ANSWERS Question 1: 1. Describe when (strip, deep strip, raft and trench fill) foundation would be used? Structural foundation is used to distribute the weight to be carried over a sufficient surface as to prevent the subsoil from spreading. Likewise, the structural foundation avoid an unequal settlement of the structure. There are various types of foundations.1 Strip foundation would be suitable for continuous loads.2 At a low depth, it is appropriate for good load-bearing strata where the soil’s moisture content is uniform. It is also used when trees are not grown near to the shallow strip foundations. This is due to the fact that trees will decrease the moisture content in the soil, thus, making the clays to contract and the foundation to settle as the soil shrinks. A strip foundation is a strip of concrete resting in a trench. The absolute minimum thickness of this strip is 150mm. Deep strip foundation would be used where the ground does not have imported soil or a wide variation in the strength of the soil in the load area (floor area or load of the building).3 In a deep strip foundation, there should be no weak soil patches since this may cause the foundation to fail. The width of the deep strip foundation has to comply with building regulations. The use of the deep strip foundations is dependent also on the size of the wall that is being intended to construct. When deep strip foundations are in the proper place, i.e. not close to trees they usually work well. deep strip foundation is a strip of concrete laid inside a trench. Deep strip foundations usually have a minimum width of 450mm although there may be occasions where a builder recommends a different width. Once this is in then 225mm depth of concrete is needed for the conservatory's foundation. Sometimes builders will recommend that the strip is deeper for greater security. Raft foundation would be used for light buildings or where the top six hundred millimeters (600 mm) of subsoil overlies a substrata of poorer quality.4 The raft “floats” on the subsoil, like a raft on water. In making a raft foundation, a concrete bed is constructed which is at least equal to the base area of the building. It is also known as foundation mat which refers to a continuous footing that supports an entire structure like the floor. In clayey soils in which a deep excavation was necessary to achieve the design level of the foundation called a “compensated piled raft”, the behaviour of piled rafts differs. Since the soil stresses reduce due to excavation, the reloading of the soil is given attention. A raft foundation has side walls (forming a basement or crawl space) of concrete, with steel reinforcing integral to the pad, forming a raft or boat. The goal in this type of construction is to end up with the soil below the building carrying the same weight as it did before the building was there. This is done by excavating the amount of soil that weighs roughly the same as the finished building. Trench fill foundation would be used if there is a high water table, where there are trees thriving a few meters away. The trench fill foundation is also used if the soil in the area is loose.5 If there may be ground heave, then the constructor will advise that the sides of the trench should be lined with a compressible material and mesh reinforcement. Trench fill foundation is a shallow foundation built through burrowing a trench and then filling it with concrete or debris. The width for payment at all sewer trench cross sections will be based on outside diameter of the sewer pipe barrel plus the following on each side thereof like 12 inches for 10-24 inch diameter pipe, 18 inches for 27-42 inch diameter pipe or 24 inches for larger than 42 inch diameter pipe. 2. Describe English bond, Flemish bond and Garden wall bond? English bond is where the bricks are positioned in a block bond. It is where one course comprises of bricks with their ends toward the face of the wall. The next course of bricks with their lengths parallel to the face of the wall. Flemish bond is where each course comprises of headers and stretchers alternately. This is so laid as always to break joints. Garden wall bond is a method of laying bricks comprising of three stretchers between each header. 3. Describe the functional requirements of a floor and explain the difference between solid and suspended floors? The functional requirements of a floor are resistance to weather and ground moisture, strength and stability, durability and freedom from maintenance, resistance to the passage of heat, fire safety and resistance to the passage of sound. There is not much difference between solid and suspended floors up to a P/A of 0.2. But for higher P/A ratios, the solid floor with a solid perimeter wall below dpc demonstrates considerably better performance than suspended floors. When using the elemental method, solid floors require less added insulation. Suspended floors are commonly made out of quality timber boards / waterproof chipboard sheets fixed on top of joists. They can also be constructed with concrete plank or post and beam. Solid floors have a more considerable stone as well as sand sub-base, cast in concrete and with the right insulation and a damp-proof membrane. 4. Define the terms "single lap" and "double lap" with reference to pitched roof coverings, and explain how they relate to the fixing of the various forms of the tile and slates? With reference to pitched roof coverings, the term “single lap“ is defined as that which only require fixing individually at pitches of 45’ (forty degrees) and over (at least one nail to each tile).6 The tail of each tile should also be mechanically fixed where the pitch is 55’ (fifty-five degrees) or greater. Where separate “over and under” tiles are used, every tile should be nailed (two nails to under tiles) regardless of pitch. “Double lap” tiles means fully-nailed (two nails per tile) in exposed locations, at pitches over 60’ (sixty degrees) or if nibless tiles are used. Otherwise. Twice-nail every fourth or fifth course. The “single lap“, and the “double lap” relate to the fixing of the various forms of the tile and slates. In a single lap tiling, one tile over another gives the weather tightness. Therefore these tiles are called single lap interlocking tiles. Generally there will be an overall reduction in the weight of the roof covering. The batten size is large than that used for plain tiles. The gauge or batten spacing for single lap tiling is found by subtracting the end top from the length of the tile. Double lap tiling makes use of the traditional tile covering for pitched roofs. They are available made from clay and concrete. These plain tiles have a slight camber in their length in order to make sure that the tail of the tile will bed and not ride on the tile below. There is always at least two layers of tiles covering any part of the roof. Each tile has at least two nibs on the underside of its head. This is made this way so that it can be hung on support battens nailed over the rafters. Two nail holes provide the means of fixing the tile to the batten. Usually, every fourth course of tiles is nailed unless the roof exposure is high. 5. Double glazing is now almost ubiquitous in modern house building. The positive aspects of the double glazing window are that there have been advances in the effectiveness of welding the joints, the design of the internal cross sections that house the steel reinforcement and improved glass coatings. On the other hand, the negative aspects of the double glazing window include the introduction of recycled PVC-U and cheap and nasty DIY fitting aids have meant that just about anyone even on the absence of budget or presence of meager budgets, all, can have double glazing installed. Question 2: Devise an appropriate drainage scheme for the removal of foul and surface water from the building to the nearest convenient main sewer. 1. Provide a drainage schedule identifying all major components of the system. Drainage Scheme for the Removal of Foul and Surface Water from the Building to the Nearest Convenient Main Sewer: To do the drainage scheme for the removal of foul and surface water from the building to the nearest convenient main sewer, a detailed calculations of surface water runoff from the development will be carried out. Likewise, the point of discharge of the existing drainage system will be investigated. As a result of the above two (2) studies, it is proposed to install a surface water storage tank which will store surface water and allow it to be discharged from the building to the nearest convenient main sewer at a restricted rate. Then the surface water discharge from the site will be required to be restricted to a maximum of 1.1 litres per second with a storage tank of minimum 5.34 cubic meters. In the same way, the position and details of the flow control devise manhole to be approved will be required. Lastly, the existing and proposed finished floor and ground levels will be controlled. Drainage Schedule and the Major Components of the System: Major Drainage Components of the System Some components of drainage components are listed below. The drainage materials needed are drainage pipe, geo-textile, catch-basins and manholes, pipe couplings, pipe anchors and the drainage gravel. Drainage Schedule a. Marking of the locations of utilities before construction. Utilities include power, telephone, water, gas, cable, etc. b. Excavating c. Commencing of the drainage system installation during dry weather periods (except in emergency situations). d. Checking to ensure that pipes have not been crushed by heavy equipment. e. Ensuring that connection is solid and not leaking. f. Checking that the slope of pipe runs. g. Water testing of drainage system before backfilling (covering with soil). 2. Relative merits and demerits of the drainage systems considered and the reasons for your selection are explained below. Include plans and cross sections to illustrate the layout and relationship between materials and components of your selected system? Table 1. The Layout and Relationship Between Materials and Components of the Selected Drainage System Merit of the Drainage System Demerit of the Drainage System Reason for the Selection of the System Plans on the Layout and Relationship Between Materials and Components of the System Cross Sections on the Layout and Relationship Between Materials and Components of the Selected System There is a significant cost in terms of poor pavement performance to agencies that are not using edge drains. The installer must check the grade of the pipe. This is done in order to confirm that there are no reverse slopes nor low points along the length of pipe. If these will not be addressed, these may reduce the performance. The reason for choosing the system is its stability. Detailed calculations of surface water runoff from the development will be carried out. The components of the selected system should have suitability with the existing materials The point of discharge of the existing drainage system will be investigated. As a result of the above 2 studies, it is proposed to install a surface water storage tank which will store surface water and allow it to be discharged from the building to the nearest convenient main sewer at a restricted rate. Require surface water discharge from the site to be restricted to a maximum of 1.1 litres per second with a storage tank of minimum 5.34 cubic meters. Require the position and details of the flow control devise manhole to be approved. Control the existing and proposed finished floor and ground levels. Question 3: 1. Calculate the “U” value of the external wall (traditional form) to the building. Describe what causes condensation in buildings and suggest appropriate measures that can be taken to control condensation? Calculation of the “U” Value of the External Wall (Traditional Form) to the Building:7 There is not much difference between the different types of floor up to a P/A of 0.2. For higher P/A ratios, the beam and aircrete block floor with a solid aircrete perimeter wall below dpc shows relatively more efficient performance than un-insulated solid or suspended floors. It allows a combination of some elements with better and others with worse U-values than the Elemental method. Under the target U-value method this floor construction can then be used, with widows, roof, boiler etc which have better performance than assumed for the elemental method minima. This produces a satisfactory over all design to meet the regulations. The other forms of floor would require added insulation to achieve a U-value comparable with that of the beam and aircrete block floor or would otherwise require the other elements of the dwelling to provide much higher levels of insulation. Table 2. Causes of Condensation in Buildings and Appropriate Measures that can be Taken to Control Condensation Cause of Condensation in Buildings Appropriate Measures that can be Taken to Control Condensation A cause of condensation is the moisture-laden air that comes into contact with a cold surface. What happens is that the air is cooled to the point where it can no longer hold its burden of water vapour. 1. Improve Ventilation Improve ventilation will sweep away the internal moisture-laden air. Then it will replace it with drier air from the outside. Mechanical ventilation such as Humidistat Fans and the PPF9 Positive Pressure System should be considered. 2. Improve Heating Heating should be set or applied to give a low-level background heat coupled with ventilation. 3. Remove excess moisture sources Possible moisture sources are paraffin heaters, indoor drying of clothes. 4. Insulate cold surfaces. 5. Prevent possible water penetration. 6. Install a dehumidifier. 7. Use an anti-mould paint. 2. Calculation of the Building‘s Total Heat Loss8 The rate of heat loss from a building element is usually specified in terms of the thermal transmittance or U value. It is defined as the rate of heat transfer (in watts) through unit area (one square metre) of the building element for unit temperature difference (one degree Kelvin or centigrade), so that the units for U value are W/m2K or W/mm2C. Kelvin and centigrade degrees are identical, however, the Kelvin notation in which the freezing point for water is 273K, is used in the current Building Regulations, possibly to confuse engineers, architects as well as contractors who have only lately shifted from Fareinheit to centigrade degrees. For convenience, the centigrade notation will be used throughout the text as it is more widely understood. Bibliography: Bright, Norman, Beam and Aircrete Block Floors - Thermal insulation Performance Concrete, Business Network, Jun 2003, TechRepublic. Brinkley, Mark, Groundworks & Foundations, Ascent Publishing Limited, Worcestershire, 2009. Curtin, W.G., Shaw, G. Parkinson, G.I. and Golding, J.M., Structural Foundation Designers' Manual, John Wiley & Sons, Inc., 2006. Emmitt, Stephen, Gorse, Christopher A. and Barry, Robin, Barry's Introduction to Construction of Buildings, pp. 48, Blackwell Publishing, 2004. Garrand, Christopher, HAPM Guide to Defect Avoidance, Construction Audit Limited. 2001. Read More