Hello dear forum,
I have a question and hope someone can help clear things up for me.
I am currently planning my foundation slab. I understand the front edge beam, blinding layer, and formwork. I have also received the reinforcement requirements from my architect. However, the instructions for the execution are quite brief.
The slab is 8 by 8 meters and 16 cm (6 inches) thick.
The slab will be made of watertight concrete C25/30. The reinforcement is structurally specified.
The entire slab is reinforced top and bottom with Q257A mats (joints are overlapped by 2 mesh widths).
Under door openings, there are two 12 mm (1/2 inch) high tensile steel bars at the top (length = effective span + 1.0 m (3.3 feet)).
Under load-bearing walls, there are two 10 mm (3/8 inch) high tensile steel bars both at the top and bottom (ring beam).
When I asked for a detailed reinforcement plan, he replied that any concrete contractor could build the slab based on the information above. To help me anyway, he sent me a 60-page technical document on concrete design for structural engineers covering all possible scenarios.
But I only need to know the spacing requirements:
How thick should the concrete cover be to the bottom reinforcement mat?
What is the spacing between the bottom and top mats?
The top concrete cover can be deduced from that.
How far should the mats be from the formwork?
Can I attach the round steel bars for the ring beam directly to the mats?
With a 16 cm (6 inches) slab, there cannot be much leeway.
Can someone help me with this?
The house only has load-bearing exterior walls.
Thank you very much,
Norbert
I have a question and hope someone can help clear things up for me.
I am currently planning my foundation slab. I understand the front edge beam, blinding layer, and formwork. I have also received the reinforcement requirements from my architect. However, the instructions for the execution are quite brief.
The slab is 8 by 8 meters and 16 cm (6 inches) thick.
The slab will be made of watertight concrete C25/30. The reinforcement is structurally specified.
The entire slab is reinforced top and bottom with Q257A mats (joints are overlapped by 2 mesh widths).
Under door openings, there are two 12 mm (1/2 inch) high tensile steel bars at the top (length = effective span + 1.0 m (3.3 feet)).
Under load-bearing walls, there are two 10 mm (3/8 inch) high tensile steel bars both at the top and bottom (ring beam).
When I asked for a detailed reinforcement plan, he replied that any concrete contractor could build the slab based on the information above. To help me anyway, he sent me a 60-page technical document on concrete design for structural engineers covering all possible scenarios.
But I only need to know the spacing requirements:
How thick should the concrete cover be to the bottom reinforcement mat?
What is the spacing between the bottom and top mats?
The top concrete cover can be deduced from that.
How far should the mats be from the formwork?
Can I attach the round steel bars for the ring beam directly to the mats?
With a 16 cm (6 inches) slab, there cannot be much leeway.
Can someone help me with this?
The house only has load-bearing exterior walls.
Thank you very much,
Norbert
You cannot build a house like this. Either the architect’s behavior is negligent, or you have misunderstood them. Your construction project requires the complete set of execution plans from the architect plus the structural engineer. The structural calculations are part of the building permit / planning permission application: construction is not allowed to begin without these calculations. Additionally, the structural engineer should have been commissioned to prepare the formwork and reinforcement plans, as well as steel and bending schedules for the delivery of pre-bent reinforcement bars. These are the details you need and have asked for.
The whole situation is very odd and contradicts any proper construction process. A 16cm (6 inch) slab is also rather undersized. If you want to build a waterproof concrete shell (often called a "white tank"), this also requires joint sealing profiles and more detailed planning, which must be resolved before construction starts. Something is fundamentally wrong here, I’m afraid. You should not accept the architect’s statement and must insist on the structural engineer’s services as described above. Do not proceed with construction beforehand.
The whole situation is very odd and contradicts any proper construction process. A 16cm (6 inch) slab is also rather undersized. If you want to build a waterproof concrete shell (often called a "white tank"), this also requires joint sealing profiles and more detailed planning, which must be resolved before construction starts. Something is fundamentally wrong here, I’m afraid. You should not accept the architect’s statement and must insist on the structural engineer’s services as described above. Do not proceed with construction beforehand.
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