I recently rendered a client's house and there has a hairline crack appeared close to the join with the old render. The client said that his house is prone to slight movement, and, has had a survey done to say it is fine. The option the client wants is to chase between the two renders and fill with a sealant/silicone (product with elastic qualities) to avoid further hairline cracks. The client assures us that the crack will not develop any further. What product would you recommend to fill the chase effectively joining the two renders. Or any advice on the situation would be greatly appreciated.
PS Great informative advice on plastering in Harrogate on Saturday, brightest bit of a very dull trade fair.