Due to lockdown I am freshening up my kitchen. The plaster coving which has been up years has hairline cracks at the joins. In the past I've covered these with paint, caulk filler etc. It Ok for a while but the cracks eventually reappear. How can I fix for longer? I was thinking of cutting a V-shaped groove that I can fill with a flexible caulk. By making it, say 2mm wide then I can get a reasonable amount in that will flex with temperature moisture etc. Is that a reasonable approach? Thanks for your help and stay well Stephen
Would be inclined to scrape a V groove as you suggested and fill with Toupret interior filler as it claims 'wont shrink or crack' have been using it for years and find that claim to be true! Screwfix stock Toupret Interior powdered filler. Fill the groove, let dry, sand to a smooth finish and refill again if required, re-sand then paint. Keep well away from caulks.
I was doing this very thing today as above. I always seal the opened joint. I use pva but if you got any wood glue then add 3 parts water and brush in 10 mins before filling. Sand. Fill over again. Sand. Paint
On coving definitely seal. The small amount of filler wiii have the water pulled out so quickly and the soft gypsum is not a great surface for filler to stick to. I've been picked up on this point before. If there is a larger area to fill thats sound then yes, skip the sealing. Narrow cut grove will need sealing to give a chance for the filler to be worked in well and stick. I've done 100s. I also seal coving joints as I go when fitting and blob them with filler so it oozes out when butted up, then it hangs wet for a few minutes. My joints never crack..
Job is done and former cracks in the coving and wall are invisible. They will hopefully stay that way. Thanks for all the advice, much appreciated. For reference what I did was: I made the cracks much larger with a multitool, ~5mm wide. Width and depth was very variable 3mm to 8mm at a guess. Coated the crack and surrounding with PVA wood glue diluted around 5:1 with tap water. I used the Toupret filler (https://www.screwfix.com/p/toupret-powdered-interior-filler-2kg/4911h ) and left it 24 hours. I could do this as I was painting elsewhere. Sanded filler There was some shrinkage, despite me thinking that I had left the surface generously proud. I added another layer of filler where it had shrunk and waited another 24 hours to fully dry. Two coats of emulsion. Stand back and admired If the crack does not appear I will be most impressed. Thanks again and stay well. Steve