Screed reinforcement is a common practice adopted to improve the strength of screed constructions, curb shrinkage and cracking and impart better impact resistance to screeds. It is the inherent nature of screeds to shrink and curl and develop micro cracks during the process of drying. Reinforcement of the screeds using wire mesh or fibres can prevent this to a great extent as they act as physical obstructions, deflecting the stress developed by micro cracks and preventing the formation of larger cracks on the screed.
PP Fibres for better efficiency
Polypropylene fibres are one of the most commonly used materials for screed reinforcement. These are especially preferred for reinforcing unbonded screeds, floating screeds and screeds laid over underfloor heating. The fibres serve to deter the micro cracking during the initial curing period. As the PP fibres act as physical hindrance, the micro cracks will deflect as it hits the polypropylene fibre and dissipate.
Mesh Reinforcement for increasing the bending moment
D49 Mesh and chicken wire are also common reinforcement materials, especially used for reinforcing traditional screeds. When mesh reinforcement is useful for increasing the bending moment, it can affect the integrity of screeds in cases where the screed depth is low. This often happens due to the formation of multiple layers at joints and corners which leads to decreased bond between the screed and the steel.
Mesh Reinforcement for Pipe Services
Mesh reinforcement is usually recommended for pipe services to reduce the risk of cracking. A 300mm wide layer of mesh over the pipes can help to bring down cracks to a great extent. However, it is important to ensure that there is 30mm screed coverage over the pipe.
Reinforcement for Day Joints
Mesh reinforcement is generally stipulated for day joints to curb lateral movement. Though D49 mesh is usually specified, we find this detail to be fairly difficult to achieve correctly. There are also health and safety issues around the use of such a product which is harmful to your eyes and skin. CSC recommends brick ties which can be easily located at the centre of the screed joint and is easy to use.