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The sketch shows a trench for a strip foundation for an external wall of a dwelling house - Leaving Cert Construction Studies - Question 2 - 2006
Question 2
The sketch shows a trench for a strip foundation for an external wall of a dwelling house. The wall is a 300mm block wall and the foundation is 300mm thick throughou... show full transcript
Worked Solution & Example Answer:The sketch shows a trench for a strip foundation for an external wall of a dwelling house - Leaving Cert Construction Studies - Question 2 - 2006
Step 1
Profiles
Answer
To set out the profiles, follow these steps:
- Establish the building line by marking it clearly on the ground.
- Set the profiles at the corners of the foundation using vertical boards or stakes to ensure accurate alignment.
- Mark the line of the external walls on the profiles for clarity.
- Ensure to measure the width of the wall (300mm) and mark this on the top edge of all profile boards to assist in establishing the foundation width.
Step 2
Test for squareness
Answer
To test for squareness of the foundation layout, perform the following:
- Measure the diagonals of the rectangular layout created by the profiles using a tape measure.
- Ensure that both diagonal measurements are equal; this confirms that the layout is square.
- In modern construction, the diagonals can also be checked against the standard CAD dimensions for accuracy.
Step 3
Width of trench
Answer
The width of the trench needs to be marked accurately as follows:
- The width of the foundation trench (900mm) is marked on the top edge of each profile board as a guide.
- Saw cuts are made into the boards at these marked positions to indicate where the trench will be excavated.
- Lines are then stretched between the profiles at these width marks to visualize the dimensions of the trench.
Step 4
How to determine the level of the top surface of the foundation
Answer
To determine the level of the top surface of the foundation prior to pouring concrete, follow these steps:
- Drive wooden or steel pegs into the base of the trench at intervals.
- The top of these pegs should project 300mm above the base of the trench to account for the thickness of the concrete foundation.
- Use a straight edge and level to confirm that the top of the pegs is level with one another.
- Additionally, make use of a Dumpy level or Laser level for greater accuracy in leveling the surface.