When is best to fill hairline cracks?

Hi Andrea, Well depending on what the surface was like before you had the walls plastered if it was solid plastering and it had many hairline cracks to begin with, it can be because the original plastering could have lost its key in areas if it sounds hollow in areas when you tap the wall were the cracks are then that could be one of the reasons also as you said the climate can have a effect on the plaster if there are cracks appearing in the coving as well the best thing to do is either get a Stanley knife an cut were the cracks are and polyfill or if you are still unsure a decorator would also be able to give good advice hopefully this has helped.

Hi Andrea, I agree with the above in that the most likely cause of the cracking is a lack of preparation to the background. If the wall already had cracking before being skimmed (I'm assuming you only had a re-skim?) then the render underneath will have blown away (come loose)from the brick work - due to age; damp issues over the years, or both. Unfortunately the cost of doing this job properly is often off-putting to potential customers as there are various costs incurred in addition to the basic skimming cost: - The old plaster and render needs removing, this incurs the first labour cost - Then this (large amount of) waste needs disposing of. Additional cost. - Then the wall needs either boarding, re-rendering - or browning off. This is roughly the same cost as the skimming itself - Then you finally get to skimming In short, to do the job properly, the costs incurred are at least double when all elements are factored in. some unscrupulous builders will ommit this information in fear of scaring off the customer and/or losing the work to someone putting in a significantly lower price. As you can imagine, the current climate serves to increase the likelihood of that happening. The unfortunate thing is, the cracks will come back regardless of how much filler you put in them. The filler is only a fraction of a millimeter in thickness, whereas the render, which is not fixed, and is the source of the problem, is an inch or so thick. It is impossible to fix it with such a comparitively tiny amount of material.