Silicone sealant, what’s to know?

Many of us do not think about the variety of sealants that are on the market. We tend to rely on builders and others to get the right one for the job. However there is a wide variety of options.

I was in the Builders Merchants close to me the other day and asked for a ‘good’ silicone sealant. This apparently required a inquisitive look from the person serving me. What, you want a good one? Are you sure? The basic one is £2 and the better one £6. This indicates that all the builders do not wish to part with the extra cash for the sake of having a better product. Bear in mind that the vast majority of the professionals will be ‘doing you a favour’ by saving you money. However, they might not actually be saving you money in the long run!

So, in support of this post I had a quick look on the internet and found a great wiki post at DIYFAQ that explains the difference between the different types and their attributes.

There are a few excellent suggestions / facts there, notable of which are:

  • Silicone is flexible, but not very good at tensile pressures. Most silicone will move 10% – so 1mm for every 10mm of silicone bead, but some claim to move up to 20%. This may well be better around doors and windows where movement is high. It also means that when sealing around a bath it is better to fill the bath first and then seal it so that the silicone is under compression rather than tension.
  • Sell by dates are very important with silicone and so be aware of this when using.
  • You can get ‘Neutral Cure’ silicones that do not smell of acetic acid. These tend to be the better ones.
  • The acetic acid in the silicone encourages mould growth and so use of alternatives is recommended for around showers etc.

So don’t just think of silicone as all the same, there are some very important differences that will affect how suitable each type is and how long it will do the job for. Long term solutions are really important for key areas like join between walls and windows. Get it wrong and water will get into the walls etc. So have a chat to your builder and maybe educate him / her on this and ensure that you get the right silicone for the job. Good luck.