Concrete and its reinforcement

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3.1.9Design of reinforced concrete

Reinforced concrete shall be suitable for its intended use. Issues to take into account include:

  1. compliance with appropriate standards
  2. end restraint
  3. concrete cover
  4. fire resistance
  5. carbonation.

Reinforced concrete should be designed by an engineer in accordance with Technical Requirement R5. BS 8103-1 can be used for the design of suspended ground floors in homes and garages.

Compliance with appropriate standards

The steel specification should indicate the steel type, grade and size. Drawings and bending schedules should be prepared in accordance with BS 8666 and include all necessary dimensions for completion of the sitework. Reinforcement should comply with the standards listed below.

BS EN 1992-1‘Design of concrete structures’
BS 4449‘Steel for the reinforcement of concrete’. Specification
BS 4482‘Steel wire for the reinforcement of concrete products’. Specification
BS 4483‘Steel fabric for the reinforcement of concrete’. Specification
BS 6744‘Stainless steel bars. Reinforcement of concrete’. Requirements and test methods
BS 8103-1‘Structural design of low-rise buildings’. Code of practice for stability, site investigation, foundations, precast concrete floors and ground floor slabs for housing

End restraint

Where the ends of slabs are cast monolithically with concrete members, surface cracking may develop over the supports.
Reinforcement should therefore be provided in accordance with BS EN 1992-1-1.

Concrete cover

There should be adequate cover to the reinforcement, especially where it is exposed or in contact with the ground.
Cover should be adequate for all reinforcement, including main bars and stirrups. No ties or clips should protrude into the concrete cover.

For concrete not designed by an engineer, the minimum cover for reinforcement should be in accordance with Table 8.

Figure 1: This is a sample caption

Table 8: Minimum cover for reinforcement for concrete not designed by an engineer

Position of the concreteMinimum cover (mm)
In contact with the ground75
External conditions50
Cast against a DPM on sand blinding40
Against adequate blinding concrete40
Protected or internal conditions25

Fire resistance

Concrete cover to reinforcement should be adequate to resist fire. Requirements for fire resistance are given in BS EN 1992-1-2.
Cover required by BS EN 1992-1-1 will normally provide up to one hour of fire resistance for columns, simply supported beams and floors.


Carbonation reduces the corrosion protection of the reinforcement by increasing porosity and decreasing alkalinity. Such corrosion can be reduced by providing as much concrete cover as possible, and by ensuring that the wet concrete is of good quality and properly compacted to reduce the rate of carbonation.