Describe how a fall of concrete flat roof is achieved??

A fall in a concrete flat roof is achieved by sloping the surface of the roof slightly to allow for proper drainage of water. This is typically done by adding a slight gradient to the roof structure during construction, or by installing a layer of tapered insulation boards on top of the concrete surface.

The slope of the roof is usually designed to direct water towards drainage points, such as gutters or scuppers, to prevent water from pooling and causing damage to the roof structure. The amount of fall required will depend on the size of the roof and the local climate conditions.

Proper installation and maintenance of the roof drainage system is essential to ensure that water is effectively directed away from the building and prevent leaks or structural damage. Regular inspections and repairs may be necessary to maintain the integrity of the roof and prevent water infiltration.

Preparation:

1. Structural Assessment: Ensure the existing structure is capable of supporting the removal of the concrete roof and the installation of a new lightweight roof system.
2. Safety Measures: Establish safety zones, set up perimeter fencing, and provide fall protection equipment for workers.
3. Demolition Plan: Determine the sequence of roof removal, including the location of strategic cuts and the method of support for the remaining roof segments.

Removal Process:

1. Interior Support: Install temporary supports inside the building to transfer the roof load to the lower levels. This includes shoring towers and beams.
2. Peripheral Cut: Cut around the perimeter of the roof at the connection point with the walls. This creates a free-standing section of concrete.
3. Strategic Internal Cuts: Move inward from the perimeter cuts, making strategically placed cuts to create smaller sections of concrete that are manageable for removal.
4. Concrete Removal: Use heavy machinery, such as excavators or skid-steers, to break up and remove the concrete sections. The concrete is typically hauled away in dump trucks.
5. Structural Modifications: Reinforce the perimeter walls or install additional supports as necessary to accommodate the new lightweight roof system.

Lightweight Roof Installation:

1. Vapor Barrier: Install a vapor barrier over the renovated deck to prevent moisture penetration.
2. Insulation: Install thermal insulation to provide energy efficiency and comfort.
3. Roofing Membrane: Apply a waterproof roofing membrane, such as modified bitumen or single-ply, to protect the roof from the elements.
4. Flashings and Accessories: Install flashings around chimneys, pipes, and other roof penetrations to prevent leaks.

Additional Considerations:

- Dust Control: Address dust generation during demolition and construction to minimize impact on the surrounding environment.
- Noise Mitigation: Use noise-dampening measures to reduce noise levels during construction.
- Waste Management: Plan for proper disposal of concrete debris according to local regulations.
- Weather Conditions: Monitor weather conditions and plan for delays due to rain or snow.