If cracks have started to appear in your render, excess water is now making its way through those cracks. Non-porous renders allow water to flow through cracks and trap the moisture behind them. The moisture builds up, causing more cracking through freeze-thaw cycles. During summer, this moisture turns into steam, accelerating masonry decay. When the masonry starts to decay, the render is no longer bonded to the wall in those areas. Further cracking can cause destabilisation, and pieces of render can fall from the building. As well as destabilising the external rendering, the erosion caused can also cause destabilisation to the masonry walls, meaning rebuilding work would be required. To repair cracks in the render, it is necessary to remove all the existing render and start again with a new render. This will ensure that cracks do not reappear in the future.