Builder caulked over grout

Discuss Builder caulked over grout in the Tiling Forum area at

Ian Barrow

Active Member
Tiler used by builder to tile bathroom grouted all corners and some developed hairline cracks. Builder has now caulked over the grout in all corners with Mapei colour match caulk. Are there any issues with caulking over grout - mould etc?


Professional Tiler
Hi, I think it has been advised previously that the grout needs to be removed from the corners then the colour matched silicone applied.
This will also be the case for where the tiles meet a bath or shower tray.
Caulk is completely different and should not be used, silicone is what is required.


Unregistered (Please Register)
I assume silicone was meant instead of caulk because Mapei colour matched was described.

Lots of tilers will silicone directly over grout. The main issue with doing this is in showers, if the grout is covered then it takes longer to dry which can cause mould.

Ian Barrow

Active Member
Your right Boggs I have posted before but builder came yesterday to replace clear silicone and I believed the grout underneath. Came home last night and he had just replaced clear silicone with colour match so cracks can't be seen.

Plan Tec Tiling

Staff member
Subscribed Member
Trusted Advisor
Professional Tiler
JOTM Winner
1- To allow movement to occur without cracking.
2- To allow full & correct adhesion of the silicone into the corner.
3- Because it is the correct, approved, tried and tested way of dealing with this situation (British Standards).


Professional Tiler
Oh yeah, sorry it’s early!

It will depend on how big a gap has been grouted in the corners.

Grout can crack with fluctuations in tempature etc within the bathroom so if the silicone is stuck to the grout you run the risk of the silicone coming away and not doing it’s job.

I leave a continuous 2mm gap on the edges and corners, when you apply the silicone this edge can be filled up giving a much better seal as the silicone is filling and covering the joint instead of just covering the joint.
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