How to seal the metal shed to the base

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Croolis

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Hello. Sorry it's another metal shed question. This time it's about sealant or other options. Took this image in the dark, apologies. Ignore the crappy corner trim thing, that's going to be covered over with a corner piece and sealed in place. That bit I'm not worried about.

What you're looking at is a corner of my metal shed that's sat on a frame of 2x4 that is itself covered by some angled white trim. There are bolts inside the shed fastening it to teh wooden frame.

Question is - you see the horizontal silver metal flashing that is coming off the metal wall base plate? I need to seal that against the white plastic trim beneath, as I'm getting water ingress through that bit, unsurprisingly. Lifting the shed in any way will be problematic now, also, the white plastic trim only goes a couple of centimetres further under the metal base plate and then there is exposed wood, so there's no sealing it inside, the wood would be constantly wetted from ingress, which I don't want. Need to seal it outside here.

I have some marine RTV that I use for my boat which is adhesive. But if using that, how to apply? I guess I could just do a big triangular bead that goes ~45 degrees from the white plastic to contact vertical part of the silver metal trim (not worried about how much to use, this tube will go off before I use it all). That way water will never get trapped behind the bead. Like a bathtub.

But I'm also considering tape, but I know nothing about it. Like a roofing tape or something, just lay tape across the seam. Would it be appropriate? I don't mind if it needs to be replaced every year or two, as long as it'll come off, wouldn't be too much effort.

As always, thanks for replies. I've had leaks through the roof screws, but am having success sealing those with roofing and gutter sealant, horrible black tarry stuff that never completely goes off (wear gloves!). Won't be using that down here. Hopefully this final problem is the end of the issues and I can actually start using the thing.


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The only lasting solution afaik is to bring the inside floor up above the level that water may enter.
 
I'll make it a bit easier - can anyone recommend me a proper outdoor waterproof sealant tape that doesn't cost an absolute fortune for 11 meters? I like the look of 3M Extreme Sealant tape but that is way too pricey. Need something that will do the same job for less money. Some sort of exterior weatherproof ducting tape?
 
Have you ruled out ingress from the red arrow areas?
The ingress can only be from under the silver galvanised steel, between it and the white trim. Below the green wall panel, at the bottom, is an air gap, but behind the green wall panel the same silver galvanised steel piece rises to form a barrier a couple of centimetres high. So any water running down the wall can only go out and not in. So your middle arrow might have ingress there where one metal base plate meets another at the corner (I'll put sealant around that area), around the rest of the shed floor it can only be water coming under the steel.

I mean, the steel is just sat on the white trim and I don't expect it to be watertight. I think I'll use tape, it's just a case of deciding which tape. I see there are bitumen based ones, but my concern is that, if in a year or two the tape fails and I have to replace, which is fine, I might have to get rid of a load of horrible left behind tack after peeling off, which is not fine. Maybe unavoidable when using any tape fit for the purpose, dunno, hence question.
 
What about something like Everbuild Black Jack or EvoStik Flashband? Looks like a 10m x 100mm roll can be had for around £12. Not sure on what it's made of, though - it might be butile -based which is the horrid black stuff that never goes off you mentioned above?
 
Is there a reason you don't want to go for the big thick bead of silicone option? That sounds the simplest option.
 
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