Will movement or temperature variations cause cracking of painted/rendered Dincel surfaces?

Conventional concrete walls crack due to the brittle nature of the material and the process typically starts while the concrete is still plastic. Unlike conventional concrete, Dincel provides an impermeable permanent skin which enables an ideal curing environment and subsequently allows the concrete to achieve additional strength and crack resistance performance. In addition to this, Dincel also provides internal crack inducers at approximately 125mm centres which cracks the concrete at controlled locations in order to act as expansion joints.

The presence of Dincel crack inducers distribute the contraction movements along the length of the wall and hence minimises the surface movement for the paint/render application. The paint/render used with Dincel should possess adequate elasticity to handle the maximum movement at each Dincel panel which is typically 0.8mm [(70-12) x 10-6 x 40°C x 333mm = 0.8mm]. Each Dincel panel joint has been designed to accommodate 1.5mm of movement. Therefore, the elasticity of the paint/render needs to be 0.8mm/1.5mm = 52% at 40°C variation. Special consideration needs to be taken for dark coloured renders where the wall surface temperature may increase significantly.

It is essential to check with the selected render manufacturer:

  • The elasticity of the system and its suitability to span over panel joints.
  • If sun-ray reflectors and polystyrene balls are used within the render to reduce temperatures (particularly with dark colours)
  • Minimum render thickness required for insulation and crack control (typically 10mm)
  • Joint spacing required for render (typically maximum 5m centres)

Further to this, a high amount of moisture inside the Dincel wall may lead to vapour trying to escape the system and cause cracks at Dincel vertical panel joints. In order to prevent this:

  • Do not use a concrete mix with a water/cement ratio in excess of 0.5 or allow for water to be added to the concrete mix on site.
  • Do not block/seal the top of Dincel Wall after concrete pouring. It should be remembered that Dincel is a waterproof container particularly after receiving polymer render or paint finish. Once the concrete has set the top can be adequately blocked/sealed to prevent external moisture (such as rain) from entering the wall.