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Preparation
Articles with simple easy-to-follow instructions and explanations.
How to prepare the ground for concrete
Example: A small shed floor:
A step-by-step example of how to make a concrete slab floor for a 1800mm x 1800mm (6ft x 6ft) garden shed.
The steps for this task are:
- Making up the formwork (the frame that borders the concrete and stops it spreading).
- Positioning the formwork on prepared level ground.
- Fixing the formwork in place with pegs.
- Digging a trench around the perimeter of the project.
- Pouring the Build Mix Concrete and placing a piece of reinforcing steel rod.
- Screeding and finishing the concrete.
- Dismantling the formwork.
Materials you will need:
- Concrete Ordered from Build Mix
- Approximately 12m (40ft) of 100x25 (1x4) or 100x50 (2x4) for the formwork, brace and pegs.
- 10 meters (30 ft) #3 rebar (which is steel rod that is 10mm (3/8") thick).
- Handful of 75mm (3") nails
Tools you will need: spade or small shovel; concrete finishing trowel; hammer; level; measuring tape; pencil; carpenters square; wheelbarrow; bucket.
Instructions
Step 1. Picture above.
Make up the formwork out of 100x20 (1x4) or 100x50 (2x4) lumber. The lumber should be straight but a low quality grade will do since it will eventually be discarded. The formwork is the frame that borders the concrete and stops it from spreading.
Tip: the formwork in this example DOES NOT have to be made up in place. It can be made up anywhere on even ground and carried in place later.
Cut two pieces of formwork lumber exactly 1800mm (6ft) long and cut another two pieces approximately 2400mm (8ft) long. Nail the four pieces together so that they make up a square with inside measurements of 1800mm x 1800mm (6ft x 6ft).
Step 3. Picture above.
Lay the formwork in place. Ensure that it is level and then secure it by hammering pointed 50x50 (2x2) or 50x25 (1x2) pegs at 900mm (3ft) intervals against the outside of the formwork.
Nail the pegs to the formwork but not all the way in, as the nail will need to be pulled out later.
Step 5. Picture above.
Saw off the tops of the pegs so that they are even with the top of the formwork. The area is now ready for concrete.
Step 2. Picture above.
Ensure that the formwork frame is square. This can be done by making the diagonals equal length. Simply measure diagonally from corner to corner (see Step 1. picture) and then measure the other opposing two corners. The formwork frame is square when the distance between the opposing diagonals are equal.
When the formwork frame is square, nail a piece of lumber on top of the formwork frame from corner to corner, to make sure the formwork frame remains square until pegged in place.
The formwork is now ready to be picked up and carried into position, but first make sure that the ground has been prepared, that is, made level, with all vegetation and any soft ground removed.
Step 4. Picture above.
Dig a trench around the perimeter of the floor area about 100mm (4") deep and about the width of the spade wide or about 200mm (8"). This is like a 'footing' to give the perimeter of the concrete floor more depth and strength, as that is the part of the floor that will be supporting the shed walls.
Step 6. Picture above.
Lightly hose (dampen) the pour area with water prior to pouring the concrete. Work as quickly as possible when placing concrete in formwork.
Example Garage Base
A. Dig down till you reach a hard surface. If one can not be found within a reasonable depth prepare the ground for a base of hard core and then compound the hard core until it is as level as possible as this will help in determinating the cost of the concrete.
B Remove any precence of water and proceed to prepare the footings which should be dug proportionat to each other. If any water/damp is present we suggest laying a polythene sheeting (viscreen) over the area prior to concrete being layed.
C. Using strong wooden boarding select the area required and reinforce the boarding with strond pigs eliminating the possibility of the weight of concrete from forcing the boards outwards.
D. Once Build Mix have placed the concrete into the selected area it is now ready to be leveled
E. Levelling in this case is simply whereby a length of wood is repeatedly raised and lowered two to three inchs using the boardomg as a source of level whilst at the same time working from one end of the slab to the other. as seen in the Picture.. This should leave a nice flush surface.
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