Caulk or silicone for soffits and facias?

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Can anyone reccimend a good exterior caulk that will take oil based gloss paint?
Or should I do my painting first and then use silicone?

Thanks!
 
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Soffits and facia should not need any caulk or silicon.?
Mine do! Just where the ply soffit meets the back of facia.... Granted, we should probably have made a better job of the timber work but it is what it is.....
 
You can buy silicones that can be painted onto so the choice is yours.
 
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You can buy silicones that can be painted onto so the choice is yours.

I think you mean that you can buy products (that are similar to) silicones that can be painted on to.

If so you are absolutely correct. MS polymers are almost as flexible as silicones and can be over painted, generally, you have to apply water based undercoat over them if you plan to use oil based paints. Unlike caulks they won't shrink back and will remain flexible.

My go to is CT1, but there are much cheaper MS polymers out there.
 

That product calls itself "hybrid", a term often used for MS Polymers. Your link is for the US website, I am , by trade, a decorator, no silicone that I have come across is paintable, unless one uses incredibly expensive specialist primers, and when I say expensive, you are looking at about £50 for 50ml

______ edit, whilst the specialist primers are expensive, I inadvertently over estimated the cost, by quite a lot. Links to one are in my next post_________
 
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So you can still buy silicones that can be painted onto then which is what i said to the OP. Up to them how much they want to spend but it is an option.
 
no silicone that I have come across is paintable, unless one uses incredibly expensive specialist primers
Just means you are not very pro. I did it for years. Here's one done a couple of years ago. Grey is the interior side silicone - it has water paint on it indicated by the intermittent white edge. The exterior silicone bead has 10 year oil gloss on it. If I get a £ every time I catch you out, I'd be a rich man.

paint-silicone.png
 
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So you can still buy silicones that can be painted onto then which is what i said to the OP. Up to them how much they want to spend but it is an option.

But the product is not a silicone sealant, it is a different class of product that shares some similarities.

Silicones are synthetic polymers made of a combination of silicon, oxygen, carbon, and hydrogen. MS polymer sealants are made from a hybrid of silane-modified polymer and polyether. Performance wise they can be likened to a cross between silicone and polyurethanes.

Silicones fall in to two camps, Acetoxy or Neutral Cure. As they cure they release either acetic acid or alcohol. MS Polymers cure through polycondensation, they use the moisture in the air to cure.

I am not being a pedant for the sake of it. The American product that you linked to may have the word silicone in its name, but it is not a silicone sealant, it even says that it can be applied to damp surfaces. Silicone sealants are hydrophobic, that means that they repel water, you cannot apply them to damp surfaces.

I do not want DIYers to assume that silicones can be painted over- they cannot, unless you use expensive specialist primers.


the above works out at £121 per 1L (although, it is available in 100ml bottles for £12).
 
Just means you are not very pro. I did it for years. Here's one done a couple of years ago. Grey is the interior side silicone - it has water paint on it indicated by the intermittent white edge. The exterior silicone bead has 10 year oil gloss on it. If I get a £ every time I catch you out, I'd be a rich man.

View attachment 310627





The first four links I found when google searching for "paint over silicone sealant" - 2 links from sealant manufacturers, one from a paint manufacturer and one from a company that specialises in applying sealants. Funnily enough, each one of them disagrees with you. Why would that be?

Over the years, there have been times that I had to force paint over silicone. I can be done, you let the paint start to thicken, then force feed it more coats. The paint is not adhering to the surface though, it is simply skinning over the silicone. If you run your fingernail over it, it will crack off.

I have no idea if the grey sealant in your image is silicone, MS polymer or polyurethane. I suspect that you don't know either. If you apply water based paints directly over silicone, you will witness the formation of fisheyes as the silicone repels the waterbased paint.

You really are out of your depth here (again). I do not understand why you are a member of a forum that has DIYers asking tradesmen for advice when you seem to believe that all tradesmen are charlatans.
 

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