Silcone sealant on top of Plumbers Mait...

15 Nov 2007
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United Kingdom
I have an old Belfast sink, sat on a stand, in the corner of my utility room.
It is tight up against the tiled wall - but there is still a fair sized gap, that water can penetrate.
The walls aren’t square, and the sink has a bevelled top, so the gap between the top of the sink and the wall is about 10mm.
This struck me as too wide for silicone - so I used Plumbers Mait instead.
I had not previously used Plumbers Mait but thought it was similar to putty, which I figured could have done the job…
I carefully filled the gap with the Plumbers Mait – and was quite pleased with the finish I got.
However, what I didn’t realise was that Plumbers Mait never sets !
I don’t expect much water to go into the gap – and I can be careful – but ultimately, I think I’ve generated an impractical solution to my problem…
I am therefore now trying to figure out how best to solve my new problem !
I could try and remove all of the Plumbers Mait – but I suspect this would be a messy job and I would still be left with a big gap to fill.
I was therefore wondering if I could just get out a small amount of the Plumbers Mait and apply a thin coat of silicone on top of it.
Would this work ? Would the silicone stick to the Plumbers Mait ?
If not, is there a better way to resolve my issue ?
Thanks in advance for any help !
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Not really…
The gap is not consistent – and its size is caused in part, by the angle of the sinks sides. The sink actually touches the wall in places – but about 20mm from the top.
I’m a bit nervous about trying to get the Plumbers Mait out. I’ve got black slate tiles on the wall and I can certainly see it messing them up a bit !
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White sprit will clean up plumbers mait, only thing that cleans your hands after useing it. It is not pants when used in the right place but this ain't it :D

Look at quadrant tiles or fill in stages with silicone, not ideal but otherwise the only answer is to skim the wall to get a straight wall and a thin bead of silicone.
I could use a mortar mix – but it doesn’t feel like the right thing to do.
The sink is likely to move a little, so if I make it too strong, the mortar will doubtless crack – whilst if it is too weak, it will eventually get washed away…

I don’t think tiles are the answer – the space is too small.

There is effectively a triangular shaped gap, 10mm wide (at the top) by 20mm deep.
I need to fill it with something – and I guess layering in silicone is an option (though it will require a lot of silicone !).
Another option would be to fill the bottom of the ‘triangle’ with something like rolled up duck tape – and put the silicone on top of that.
My thought was to use the Plumbers Mait as the ‘base’ – but I’m guessing from the lack of positive responses, that this is not considered a good idea !!
If you don't think that quadrant tiles will work, how about some of that sealant strip, that you can get for sealing along baths etc.
this kind of thing.

If you want to fill behind as well first to make a good surface to stick it down to. I'd suggest two part polyester filler - aka car body filler or two part wood filler. OK I know if sound like a bodge ;) but it is pretty useful stuff. Sets quickly, seems to have a little flexibility so doesn't crack easy, sticks to things well, easily sanded, pretty water resistant.
Galoka, that is a very good idea... (not sure why I didn't think of it myself !)
In my mind, I always think that those strips need to go on before the tiles - but I know that's not necessarily the case.
I will certainly check out the options properly and see if I could get one to work.
Thank you.

Just before I let it go, can anyone categorically confirm that putting silicone on top of the Plumbers Mait is not a clever thing to do...?
Just before I let it go, can anyone categorically confirm that putting silicone on top of the Plumbers Mait is not a clever thing to do...?

It's probably work ok to start with, but I reckon it will ust lead to earlier failure and you having to redo it, and which point you've got silicone and PM to remove.. Anyway I reckon 10mm is a big gap to fill with silicone and have it look at all decent
I guess early failure is a definite possibility. I was just hoping to avoid having to scrape out all of the Plumbers Mait (mainly because of the fear that I will get it all over the tiles).
I did some measurement last night and the gap is at least 10mm – it is 15mm in places – so I would end up with a fair wedge of silicone in there !!

I’ll check out the edging strips properly today or tomorrow. I may find one that I can apply on top of the Plumber Mait – which would be the perfect solution !
Never have done this but kind of think it worth puting out there for others to think about or.. Gripfill, then the next day, a covering of silicon ?
I could try and make a wooden quadrant to fill most of the gap - and then put the silicon on the top of that.

The trouble is, however I handle it, I'll still be left with a 10-15mm width of silicone at the top - which is a lot !!

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