Help with interior & exterior sealant on living room window

[Mr. Clueless]

So earlier in the year we found that we had a leak on the main living room window. Water wasn't gushing in but it was bad enough that we needed to stick a towel down to mop it up.
Once the rain stopped & we got a dry patch I just bodged some silicone around where it was leaking (it was actually leaking at the top of the window - where the wall face juts inwards).

I know they say you're not supposed to silicone over silicone & that it wont stick ... but it stuck & improved but didn't 100% fix the situation. It still leaked a little later on but not nearly as bad.
So this was a bodge with the intention of 'doing proper' come summer.

As a DIY donkey my issue is the dashing. Removing sealant is one thing when it's in the kitchen where a nice flat worktop meets a nice flat tiled wall & you can scrape at it easily.

But this is dashing where the silicone is just embedded everywhere.
I actually think it's possibly leaking a bit on the bottom too where this photo shows but the initial leak was most certainly at the very top of the window.



So the question here is I assume to re-seal the window on the outside I need to remove ALL the sealant - both uprights & across the top? Even though the left & most of the top seem to be ok.
If so then how do I go about that with it being all over the dashing & I can't so easily cut it away?


Also while I'm asking then I may as well ask about the interior too. Obviously leaks come from the outside not inside. Would I need to remove ALL the sealant on the inside as well to redo this? Would you even bother? I mean it's not really like anyone is coming inspecting it but at the same time if it needs doing then it needs doing.


Finally - recommendations on which sealant to use? Certainly outside & if it needs doing then inside too?

 

[Wayners]

I think id put some hard thin cardboard up the frame to protect then use a multi tool with a masonry cutter coming out 5mm.
Scratch the rest off with a old screwdriver.
Just need a channel to get some silicone in tidy.
Use the correct silicone for widows.

Inside use interior window mastic not silicone.

 

[Mr. Clueless]

I think id put some hard thin cardboard up the frame to protect then use a multi tool with a masonry cutter coming out 5mm.
Scratch the rest off with a old screwdriver.
Just need a channel to get some silicone in tidy.
Use the correct silicone for widows.

Inside use interior window mastic not silicone.

Have I understood you correct - are you saying basically cut in to the render / get rid of a section of the dashing?

I can scrape off silicone in a bathroom or kitchen no problem. I can apply it no problem. But getting in to re-rendering or whatever then that's not me unfortunately. I can't do that.

I assume I can't just wash it down (get rid of the grime), dry off & then apply new?
or that I can't just peel off as best I can & then apply new?

For the interior, is that going to be a requirement in terms of leaks or just an - it'll look tidier if you do kind of thing?