How much steel required for 400 sq ft slab at 4″ & 5″ thickness | how to calculate steel required for 400 sq ft slab | how much steel do i need for 400 sq ft rcc flat roof slab | calculate the quantity of steel required for 400 sq ft roof | how much steel needed for 400 sq ft roof slab.

Rebar is short form of reinforcing bar, it is steel bar or Steel wire provided as tension bar, used in reinforced concrete structure like column, beam and slab of house construction and it also used in reinforced masonry structure. It is used to increase the strength of concrete structure.

Actual Steel calculation is based on as per design but if design is not given then Steel calculation is based on Thumb Rule on experience basis.

In roof slab reinforcement we provide there is a two types of Steel bar used main bar and cross bar.

1) Main bar:- main bar is also called as shortist span bar usually used at bottom of slab having spacing 4 inch between the two bar. Main bar is also called tension Steel because it is provided in tension zone of roof slab in bottom having tensile strength of steel is enough yield strength and ultimate tensile strength.

We should use higher tensile steel in main bar Fe550D. sufficient amount of main bar used in shorter direction having 10 mm or 12 mm dia of Steel bar according to roof slab reinforcement.

2) Cross bar:- cross bar is also called as longer span bar or distribution bar or cross bar mainly used at top of the main bar in compression zone of slab, cross bar usually dia of 8mm or 10 mm bar Steel bar used in longer direction according to roof slab reinforcement.

Actual Steel calculation is based on as per design but if design is not given then Steel calculation is based on Thumb Rule on experience basis. In this article you know about how much steel required for 400 sq ft slab at 4″ & 5″ thickness

**How much steel required for 400 sq ft slab at 4″ & 5″ thickness**

According to Indian standard rcc concrete roof slab thickness in residential building construction is 4 inches (100mm). Use of 5″ to 6″ (125mm to 150mm) is recommended if the concrete will receive occasional heavy loads.

Thumb Rule for Steel in RCC slab :-

Generally Thumb Rule for Steel in RCC slab construction is ranging between between 80 kg to 90 kg per cubic metre per wet volume of concrete of RCC slab.

**How to calculate steel required for 500 square feet slab**

1. Convert thickness in feet

2. Calculate wet volume of concrete = square footage × thickness in feet

3. Convert cubic feet into cubic metres

4. Taking steel quantity 80 kg to 90 kg per cubic meter volume of concrete

Assuming it a normal residential building with light loading conditions, thickness of slab will be 4 inch thick. For example if your plan area = 20 × 20 = 400 sq ft, so for the plan area of 400 sq ft total volume of concrete required = 400×0.33 ÷ 35.3147 = 3.74 m3, as per thumb rule 80 kg to 90 kg of steel are required per cubic meter volume of concrete, so as 80 kg × 3.74 = 300 kg or 90 kg × 3.74 = 337 kg, thus, you will need 300 kg to 337 kg of steel required for 400 sq ft of rcc roof slab at 4 inch thickness.

**Conclusions**:-

As per thumb rules and generals guide line, for a 400 sq ft rcc roof slab at 4 inch thickness, generally you will need 300 kg to 337 kg of steel quantity. Thus 300 kg to 337 kg of steel quantity are required for 400 square feet slab at 4″ thickness of normal residential building with light loading conditions.

For office, school building, steel may increase marginally due to live load condition,thickness of slab will be 5 inch thick, so for the plan area of 400 sq ft total volume of concrete required = 400 × 0.416 ÷ 35.3147 = 4.72 m3, as per thumb rule 80 kg to 90 kg of steel are required per cubic meter volume of concrete, so as 80 kg × 4.72 = 378 kg or 90 kg × 4.72 = 425 kg, thus, you will need 378 kg to 425 kg of steel required for 400 sq ft of rcc roof slab at 5 inch thickness.

**Conclusions**:-

As per thumb rules and generals guide line, for a 400 sq ft rcc roof slab at 5 inch thickness, generally you will need 378 kg to 425 kg of steel quantity. Thus 378 kg to 425 kg of steel quantity are required for 400 square feet slab at 5″ thickness of normal commercial building, office, school building. Steel may increase marginally due to live load condition.

For office, school building, steel may increase marginally due to live load condition. For multistorey buildings, steel will increase further. With increase in span and load, thickness of slab will also increase.

But as a thumb rule, for normal slab, it is 80–90kg per cubic metre volume. More simple formula for residential flat, steel required in kg = area of slab in sft. This will give maximum limit. You can take 85% of it for normal residential building with 3 meter span.

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**Final conclusions:**–

As per thumb rules and generals guide line, for a 400 sq ft rcc roof slab at 4 inch thickness, generally you will need 300 kg to 337 kg of steel quantity and at 5 inch thickness of slab, 378 kg to 425 kg of steel quantity are required.