Mastic where wall meets shower tray. How often to replace/repair?

[Chap sur le velo]

So before my recent holiday noticed evidence of leak on ceiling below bathroom. Sorry for long winded here, but as often with water leaks its hard to be 100% you've nailed the source.

Obvious candidate is Shower tray, inspect and see some loose 'frilly' mastic, so taped shower doors closed.
Hoowever once on holiday, Duaghter contacts to say the hand basin tap is leaking. With the help of Whatsapp from India I got her to isolate the tap.
No more visible water. Ceiling below, discoloured but dry on our return.


THIS IS FINALLY MY QUESTION...What to do about the mastic in the shower? (Which is now totally dry as we've yet to put the shower back in to operation.)
About 4 years ago I had a leak here and spent some time sorting out the mastic where the tiles meet the tray in a Victorian house. Note its a stone tray on a wooden floor in an old house so movement is possible. Checked youTube and after scraping out old and allowing to fully dry.
I applied in two stages. Frist run, fine nib to get mastic right into the gap. Then before that's dry apply a second course with a larger nib and smoothed over. Now in a couple of places the top edge is 'fraying'. Naturally due to the history of the house I assumed this was where the water was leaking.
Now I'm not sure it is leaking but wondering if I should apply a 3rd course of mastic over the top? Will it stick? Do i need to scrape out old and start agian to be sure?
Hoping it will give another 5 years before it leaks. What is a reasonable lifetime for shower mastic?
Thoughts welcome, thanks

 

[fossyant]

Be better to remove that second layer and re-apply.

 

[newts]

Clean off all the old sealant, make sure it's clean & dry before applying a quality sanitary grade sealant (Dow 785 is the go to silicone sealant). Mildew on the sealant is inevitable. If mildew reappears quickly it would indicate insufficient ventilation/high humidity & /or substrate issue, damp behind the tiles.

 

[Chap sur le velo]

Be better to remove that second layer and re-apply.

YEEEEEES but there's so much I want to get on with now!!!!!!!!!!

You of course are 100% correct. And it will save time in the long run....drat!

 

[fossyant]

Leaks are a pain. We've had some mainly from the 'top hat' nuts under the taps breaking, allowing water through, then one holiday, a tap wasn't quite switched off, so there was enough of a drip for it to track back along the tap, onto the bath top, on the floor and through the ceiling over two weeks.

 

[raleighnut]

A 2nd vote for using good quality silicone, that cheap stuff just doesn't last so is a false economy

 

[sheddy]

What’s the fastest way of removing old sealant ?

 

[raleighnut]

What’s the fastest way of removing old sealant ?

Silicone eater, just paint it on and wait 10 minutes comes off easy-peasy

EDIT some is available in tube form, others in Liquid

 

[Dadam]

Silicone eater, just paint it on and wait 10 minutes comes off easy-peasy

EDIT some is available in tube form, others in Liquid

Damn, would have saved me an hour or two of swearing and sore fingers last Saturday resealing my mum's shower tray.

 

[newts]

We use single edge scraper razor blades (carefully!) to remove most of the sealant, then soudal sealant remover for the rest. Final clean with isopropyl alcahol before reapplying sealant.

 

[Beebo]

You have to remove the easy bits by hand then as above use silicone remover which will break down the final bits. Which can then be scraped off.
I do this probably once ever 5 years just to keep the shower looking good and stopping problems before they arise.

I am still rubbish at applying the mastic even after watching loads of YouTube videos. I can’t get a consistent bead.

 

[presta]

My bath is sealed to the tiles with silicone rubber, not mastic, and it's still watertight after ~45 years.

 

[neil_merseyside]

Silicone only has a relatively small movement tolerance so the bead needs to be scaled so that the amount of movement can be accommodated - so small beads are generally out! Sealant best applied between 2 strips of masking tape with gun pushing as a plough forcing sealant down into gap, then peel tape carefully (damn messy!) then spray bead well with water (with a dash of detergent) then smooth the tape edges with a wet thumb or a proper beading tool.

 

[slowmotion]

I wouldn't apply a bead of silicone over existing silicone. Aim to get one bead on of sufficient size to allow for movement.

 

[fossyant]

Beading tools are great provided there is nothing in the way, like raised edges and taps.