Grout failed, replace grout or mastic it?

[bionicnemonic]

Hello
We had a slow leak from the grout in our shower...until I bashed the skirting board with the vacuum cleaner and it crumbled I didn’t know. Unfortunately the insurance wouldn’t cover it as it comes under ‘maintenance’ (unfortunately I don’t regularly check the grout for invisible permeability!) Anyway! I need to repair this (and the door frame skirting board) Can anyone advise, do I scrape out the grout and put more grout in or should I lay a bead of water proof mastic down (it’s in a false wall corner)? It’s truly dry now (not used the shower for months) thank you!

Bumping!

Grout is not suitable for corners where movement may be present especially if there's no waterproof layer behind. Ideally the substrate would be tanked before and the tiles would just be a screen, but if not it would be better silicone.

I used glue/grout (used to adhere tiles as well as grout) for flat areas and then silicone in corners and at bottom where joins the shower tray. You can get tools to get the grout out provided there is a wide enough gap between tiles (often reason grout goes is that this isn't a big enough gap so too little grout in there) I just used a stanley knife though as my gap was too narrow - just wear eye protection either way due to dust and grit and if the blade breaks. I have had to do it twice in 10 years (went in different places) but it is too big a job to replace all tiles (for me anyway).

Originally I actually took out bottom layer of very large tiles on one wall of shower in lower section - scraped off useless non waterproof adhesive/grout, cleaned off tiles and re did it all with better quality materials. But at the end of the day its on wooden floor boards so movement and cracking is inevitable.

There is a definite knack to sealant so if you haven't used before practice if you can.

Yes agree, the knack to silicone came in the form of the"Cramer" sealant tools! About 20 quid from Amazon

Fantastic help-thank you! Yes the tiles in the corner don’t meet up very well. Have ordered the Cramer tool-which is obviously something I should have found decades ago-the number of spoons I’ve used! 😁 Many thanks!