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Anything Better than Caulk Against Upvc Windows/Doors?

Evening all.

Have become fairly adept at applying decorating caulk were needed but even where the application has been good and subsequent paint lines good, I find that after 2-3 years, the caulk starts to crack (or more accurately speaking lift) from the edge were the plaster meets the Upvc fitting. … e.g external windows & doors…don’t have the problem anywhere else.

It’s a fairly neat lift…virtually a straight line…and where the lift is pronounced, you can tear it back in a straight line. In other areas it just shows as a hairline.

I’m guessing its to do with differing expansion rates between the plaster and Upvc?

Question is…how to fix that properly and as permanently as possible?

Whilst I’ve upgraded my filters, primers and paints and tools the last year, I’ve never been in the slightest bit selective with caulk.

Is there a difference between differing types of caulk?..

…Is there one that’s ‘THE’ one to use? …

…Or indeed is there a special format one for this specific application?

…Is there a prep technique that can head off this lifting / cracking … or at least minimise it?

Wading through our kitchen refurbishment and want to head off this sort of stuff for future.

As always your help and input towards OCD hell is appreciated. :wink:

You could give Everbuild exterior, overpaintable frame sealant a try. I use it for all caulking jobs. I think all caulk, and even the above sealant loose their flex over time, Good luck


This the one you mean Zen?

Yeah I had a feeling it might be a bit of a live with thing in a way…it seems way more pronounced were plaster meets Upvc fittings.

Also just seen and read the TP article on emulsion paint and caulk which has some useful pointers in although it seems more about issues with paint application…I don’t really have any issues with the paint strangely, just the actual caulk itself lifting at the joint line over time.

And just looking again, the lift is not actually on the Upvc window, it’s at the plaster edge…which I’m thinking does make some sense as the plastic window would likely expand more than the brick & plaster…pauses to mentally index HND Mechanical engineering from 1981…and finds???..not much to substantiate that!! :grin:

In the article it mentions some products I’ve tried for look for…some successfully, a couple not. Products it mentions are as follows:

Soudal Acryrub Decorators Caulk Acrylic…easy to find

Repair Care Dry Seal can see a web site but not 100% sure which is the right product…

Den Braven Anti-Crack Sealant…

I’m keen spend a little time getting the choice refined to the best for my problem as I’m Presonett Joint fillering the entire walls/ceiling x 2 and Eico’ing the lot…so would prefer avoid any rework later…as far as that might be possible as Zen mentioned earlier.

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The Repair Care products are belt and braces, recommended.

The Soudal acryrub flexes about 15% which is mad. The site UK Sealants is a reliable source. The guy who runs it, Alistair, knows his stuff about all and every permutation of caulk and sealant, and his Soudal product is the trade formulation. I say trade formulation, because B&Q sell “the same” which may well be a retail version, (it has been known for manufacturers to sell lesser product to the sector of the market that really could do with the best products!). Either way, what was used in our case studies didn’t come from B&Q.

Does the cracked caulk of which you speak break away from the paint, or has the paint lifted with the caulk? I am sure you can see where I am coming from, when redecorating, make sure you aren’t caulking onto a dodgy painted plaster substrate.

Did you see this article on caulk. it is a cracker, excuse the pun.

Thanks in general for your indepth input.


Hi Andy, yes I read the article…it was that that pointed me towards those products.

No the paint/caulk relationship was perfect…in fact I’ve never had that on any of my paint work. It was the caulk lifting entirely from the plaster edge. When I say entirely it was a fraction of a millimeter but visible…in a bad way. The plaster was well laid by a pro about 10 years back. It could be I didn’t clean it as well as I’d like to remember I did :smirk:

On the repair care range…which item specifically should I use for the Upvc / plaster edge caulking? Was struggling discern the range elements…like their video but the range was confusing.


It this the product folks are using as alternative (or upograded) caulk Andy?

Can see they have a comprehensive range of ‘stuff’…working out what ‘stuff’ to order is a little easier said than done for us aspiring amateurs :smile:

Hi for the anti crack sealant you can buy from decorating direct, we use it all the time found it excellent.

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Is that the Den Bevan one Jason?

Yes ,I buy a box ,give it a try and see what you think.cheers

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Definitely will…thanks Jason…can see myself ordering 3 or 4 and trying the lot during this week :grin:

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@charliebudd has a lot of insightful info re the use of Repair Care Dry Seal for caulking between glazing bars and glass, bridging two different surfaces

Repair Care Dry Seal is a bit trickier to use than caulk – it’s a lot
thicker – so a geared gun helps massively, and it’s harder to spread.
But once you get the hang of it, it’s brilliant. I now use it to seal
between glass and glazing bars on interiors – I know it’ll dry within 2
hours, it’ll stick really well, it’s a sealant so even when the paint
fails it seals – no brainer really, even at £12 a tube!
A quick tip – using a silicone spreader helps spreading it and
getting really neat profiles. I have a Yato set which is getting a bit
ragged now, I’ll order another set tonight while I think of it!

It is a bit messy and time consuming, but practice helps a lot!
I use Dry Seal for interior and exterior glazing gaps and beads. I just know I can trust it.
In the summer when doing exteriors I often have two tubes on the go
with different nozzle hole sizes – one for doing large beads when I’m
replacing putty, and one for smaller gap filling jobs. I find the nozzle
sizes fine.

(Taken from these comments)

(Judicious use of masking tape would help if you are concerned about free hand application.)


Hi Andy yes I read Charlie’s comment on the Repair Care stuff a few times in the past but had lost them again. Thanks for the links.

Sorry yet more questions if I may at the risk of taking more of your time:

I don’t mind the tape up or time…is the result that counts for me so happy to buy and do. In fact I think I’m going to take all three of the suggestions and give them all a go at the risk of sounding a bit over the top. it can be a ‘caulk face off’ :smile:

An example of a geared gun with the strength to push sluggish material out

I’m out of bullets now on this one and maybe time for @amateurhour64 to release the test dogs!

Dry Seal MP is flexible and adhesive; the acryrub is in a similar ballpark for flexibility as the repair Care range and dead easy to apply (in that it is a standard consistency caulk) ; trying to get some more feedback on the Hippo 3

The more I think about the “best” product for this scenario, though, the more I am inclined to wonder, why haven’t we mentioned Toupret Fibacryl (formerly they had Elafib)? Rake out the crack, apply the flexing filler, bed the Toupret scrim in vinyl matt emulsion tight up to the joint and over skim, and away you go?


Ok now I got more options than I know what to do with! :grin:

But have to say the Toupret solution strikes me as a solid way forward if more time consuming. I used the scrim and paint formula stolen from your flat walls article very successfully. And I notice that Toupret also do Fibracryl in a 310ml cartridge as well.

In my case I think some masking will be required to achieve the clean line against the Upvc but otherwise it seems a great way to go to prevent the expansion crack/flex at the plaster edge.

Scrim got…Fibacryl about to be ordered…let you know how I get on.

Is a great way of looking at the problem through the other end of the telescope. Cheers Andy

Re the Hippo, had this feedback

stopped using Hippo a while back as I had a few occasions where it yellowed through the paint film - I spoke with their technical department a few times and they were not that helpful so switched to Repaircare MP and Dunlop Acrylic sealant.

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Hi Andy and thanks for following up on this one.