I did a little favour for someone and raked out some cracked grout for them and quickly re-filled with some of the unibond pre mixed stuff that was kicking around. They didn't use for 48 hours but a week later they have noticed the grout is turning yellow!

Any ideas why?

I am going to go back and remove and re do and replace with something else but wondered if it was an underlying problem?

Any thoughts welcome.

Cheap Grout and maybe contamination from previous grout.

was the water clean that you washed off with?

did you completely remove the grout from the joints ?

to be honest I probably did not completely remove the existing grout but just cleaned out the lines where it had cracked and re filled. I take it the job requires complete removal of existing grout and re application? Will the whole shower cubicle need to be re-done?

A few possibilities, contamination from the substrate and or other materials, dirty water used for mixing and or cleaning, cheap grout, and maybe something other than these.

Hard to say for certain, a few more details needed.

Originally Posted by liverplum

to be honest I probably did not completely remove the existing grout but just cleaned out the lines where it had cracked and re filled. I take it the job requires complete removal of existing grout and re application? Will the whole shower cubicle need to be re-done?

You posted this as I was typing lol, obviously if the old grout was discoloured this could be the cause of the new grout discolouring, you will need to remove all of the old grout yes. How much of the shower is affected ? it will probably be best to redo the lot but what has caused it in the first place ??

have they been cleaning the grout/tiles with bleach

Why not try a grout colourant from Mapei or Aquamix ?

I've never used a grout colourant....

Quite why the grout had cracked int he first place I am not sure. It was done originally around 6 months ago and I guess maybe because the grout was already going off when applied or not mixed correctly or cheap ready mixed stuff maybe?

hi were exactly is the grout in a shower and is the grout in the corners

could be movement in the wall .
i would use flexi grout to re do it.

Originally Posted by kilty55

have they been cleaning the grout/tiles with bleach

My first thought also

ill ask re the bleach - its around the bottom of the shower cubicle possibly where the upstands of the tray are - something to do with movement why they cracked originally? Recommended flexible grouts?

the bottom of the tray should be siliconed not grouted,,if its grouted this is why its cracked,,yes a flexi grouts needed but if its also going yellow itd suggest they are cleaning with a bleach based solution

i,m sorry I didn't make that clear - where the tray meets the tiles it is siliconed but the upstands come up maybe 3 inches behind the tiles and it is that line a couple of inches above the tray where the grout has cracked.....

all internal corners and were tiles meet a different surface (shower screens vanities bathes shower bases) should not be grouted these joints should be silicon ed hope this helps

so have my teeth

Originally Posted by liverplum

i,m sorry I didn't make that clear - where the tray meets the tiles it is siliconed but the upstands come up maybe 3 inches behind the tiles and it is that line a couple of inches above the tray where the grout has cracked.....

sounds like the start of water damage does the base flex or the walls

Doesn't sound good!
It didn't move as far as I could tell - i'll need to have a more thorough investigation of that when i'm there next.

Could quite a small amount of movement in the tray would transfer up to the upstands and could move them enough to just crack the grout line along that level?

If I remember correctly some of the grout below that level had cracked as well so I think it may have just been applied once it had dried out too much towards the bottom of the shower?