Mystery material under silicone

[SuperNoviceDIYer]

Hi

I am trying to re-grout and re-silicone my shower enclosure because there is a very slow leak to below and the grout is cracked in places. I had been advised it was likely that water was seeping through cracks in the grout.

The silicone I had already tried to replace and it was my first time doing silicone and was a mess (although the same professional said it was watertight). It had also started to go yellow/brown after only about 9 months. Hence wanting to do both the grout and the silicone.

I have now removed the silicone and the old grout but I am confused as to what is under the silicone, where the tiles meet the shower tray and wonder whether I should try and remove it to give a better finish with the silicone. Advice online seems to suggest to me that those kind of gaps should be filled with silicone to allow for movement.

It is a dark brown colour and almost looks like cement? But it has cracked a bit, is crumbling and uneven in places. It seems a lot harder a material than grout as when I try and attack it with the same multi tool blade used to remove grout it doesn’t budge.

I include a photo, the blue highlighted area is the mystery material and the green is an example of where I have removed the old grout. I welcome any thoughts on whether I should be trying to remove it or just doing a neater job of silicone-ing over the top.

 

[footprints]

Might be previous brown grout or adhesive if it is sound just silicone over it.
Remember to fill the bath at least half full before applying silicone and leave the water in overnight, so the bath will spring up to compress the seal rather than pull away once you and the water are in there.
Lots of posts on here about applying silicone have a look for some more tips.

Mine would be clean with methylated spirit, use a good masking tape like Frog tape, apply the bead smooth with the MK1 finger dipped in a container of water with a tiny drop of washing up liquid (you will find five different sized and shaped ones supplied with each hand) clean your finger off with rag after each pass. Peel the tape and chuck it in the bath water till you have time to clean up, then VERY lightly smooth along the silicone to get rid of the slight raised edge from the tape. Again wipe your finger clean and dip in the container between each light pass. You can do the first wipes with snug fitting disposable gloves but you will only get a good finish with a bare finger.
Lots of tools out there to replace fingers but I have tried most and come back to digits every time.

Once you get it 90% right quit, if you keep messing with it you will just **** it up!

I have never suffered any problems from silicone, but if you are concerned or know your skin is sensitive stick to the tools.
Big Wipes are great for cleaning hands and anything else you get gummed up with silicone!
https://www.mypaintbrush.co.uk/big-...MIru6k6_aS3wIV4inTCh2AfwUCEAYYBiABEgIsffD_BwE

 

[SuperNoviceDIYer]

Thanks so much for your response, very helpful.

When you say ‘sound’, does that include it being uneven and crumbling in places?

It is a shower tray rather than a bath but presumably I could put a couple of buckets of water to weight it down a bit?

 

[footprints]

I would scrape out any loose or crumbling stuff but you said it was harder than the grout so I assume most is firm.
A couple of buckets of water or some heavy tool boxes on some padding will help to hold down any movement in the base .

 

[foxhole]

Should not be anything other than silicon where tray meets tile, ideally tray sealed with silcon against background [wall] and then sealed again with tile.