The answer to this question could well be both yes and no. If we assume that you are going down the no root this might not be the best way to proceed. It’s understandable why you wouldn’t want to have to bother with the removal of old Silicone Sealant as it can be a time consuming job. When faced with the prospect of being stuck in the shower or bathroom trying to hack the lumps of discoloured and unpleasant Silicone Sealant out of the gaps between the unit, the tiles and the wall. However if you just simply try and stick the new on top of the old you’re going to end up having to do it all over again some weeks later. There is also a very good chance that the new sealant won’t even stick to the old and you’ll have to remove it anyway.
If only there was an easy way to remove old Silicone Sealant to make way for the new. Well, good news, there is Silicone sealant remover on the market and it’s available for commercial and residential use. https://www.ct1.com/product-applications/how-to-remove-silicone-sealant is one to the many options that you could go for. With its application you can easily start to remove the old Silicone Sealant and begin the prep work for the new Silicone Sealant to be applied.
This might seem like a lot of hard work but it is certainly worth the effort and end result. You’ll have a nice new sparking bathroom again with no water able to leak down the sides and create mold growth.