If you are using wheelbarrows to ferry the cement then place planks along the edges where there is soft bedding such as fill material o prevent loose soil falling into trenches due to the weight of the wheelbarrows. When placing your concrete there are a few things to consider.Ĭlear the soil that was excavated well away from the edges of the trench to stop it falling back into the trench and contaminating the concrete. See our tables here: Concrete mixes by weight & volume Placing Always add an additional 10% to allow for wastage and unforeseen circumstances. When you have finished the excavation measure the actual depth, width and length of the trench, and calculate the actual volume of concrete that you will need. This wii require more concrete than estimated and will be a waste.
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Trim the sides of the excavation to avoid holes being filled with concrete on the side faces. Trench sides and must be as near to vertical as possible. For a double storey building reinforced foundations would require 25–30MPa. The strength of the concrete used for unreinforced strip footing must be at least 15MPa or better. The average minimum thickness of the foundation must be at least 200mm. The minimum depth of the strip foundation trench must be at least 400mm below the original ground level. Sloped trenches must not exceed 1:10 gradient. Trenches in sloping ground can be stepped with a minimum of 400mm overlap. If a reinforced concrete roof is required on the house then the minimum width is 750mm for external walls and 600mm for internal walls. THE NHBRC (National Homebuilders Association Council) requirements for house foundations:įor single storey buildings with a tiled or sheeted roof in stable soil conditions, the minimum width of strip foundations should be 500mm for external walls and 400mm for internal walls. These foundations are for external brick walls around a new house, or for extensions of an existing house. This guide will help owner builders to cast foundations. A Concrete Placing Guide Neatly dug foundation trenches with steel reinforcing in place.