Grout that cracks

[Ankan_77]

Hello!
I've been doing some carpentry at home. Built-in closets etc., but I always encounter the same problem. The caulk cracks after a while. I suspect it's due to the building material shrinking. In the picture here, it's MDF against the ceiling, and caulk (acrylic or latex, don't remember but maybe it's the same thing?)
The closets are on a base made of regular wood beam. Built 3-4 years ago.
How can I avoid these ugly cracks?

 

[Peter2400]

The problem is mostly due to the fact that you've used latexfog. It's essentially like thick paint, and once it has completely dried, it becomes inflexible and cracks. Use a proper building sealant like tec7 instead.

 

[Ankan_77]

Oh, great! Thank you so much for the tip. I will try it next time.

 

[Mazen]

Tec7 is an MS polymer and it works great as a sealant, there's a good thread here on the forum if you search a bit.
Biltema has an MS polymer sealant that is good and much cheaper than Tec7.
https://www.biltema.se/bygg/kemikal...MIteOg_5v07wIVwQyLCh0VignIEAQYASABEgI3UvD_BwE

 

[Mazen]

Here's the thread I was buzzing about..
https://www.byggahus.se/forum/threads/perfekt-mjukfog-handledning.365348/

 

[Ankan_77]

Here is the thread I was buzzing about..
[link]

Awesome! Really detailed
Thank you so much!

 

[Ankan_77]

I am still surprised that I didn't find this earlier.
I think I got the advice to use acrylic sealant a while ago at a place like Bauhaus.
But what should latex/acrylic actually be used for then? Feels doomed to fail.

 

[Mazen]

Alcros paintable sealant/latex works well when painted in, e.g., between baseboard/cornice and wall. But as a joint between woodwork, MS polymer is the best..

 

[hapazard]

Worth knowing is that MS is much stickier than acrylic, but if you apply it and wipe with denatured alcohol it won't be sticky.

 

[Mazen]

Or buy wet wipes like Eldorados for a tenner.

 

[TechChad]

Wiser today than before! I have always used Akrylfog and have always been bothered by it cracking, but I will try MS polymer!

 

[nameloser]

Always used latex/acrylic sealant indoors. Initially, I tried various mid-range brands and they often cracked after a week or so. Then I was recommended ESSVE Flex 25% and have exclusively used it since. I probably have a couple hundred meters of sealant in the house (among other things, I have no ceiling moldings) and not a single crack. Not only does it hold up the best - it is also, in my opinion, the easiest to work with. It is in the upper price range for acrylic sealants, yet at least half the price compared to tec7 - which is also much more difficult to work with and stickier. That said, tec7 is my first choice for various outdoor situations.

 

[Ankan_77]

Since I already have you "on the line". I previously didn't have any decent cutting tools (just a handsaw and a bad jigsaw) so I always asked places like Bauhaus to cut the MDF. I've "played it safe" and preferred to cut it a bit too short rather than too long, so sometimes it ended up 1 cm too short. What's best here? Fill, sand, and paint? I initially thought it was the filler that cracked, so I used latex sealant. Well, that didn't work out so well.
What advice do you have here? (Yes, apart from measuring and cutting properly...)

 

[Mazen]

1 cm is quite a lot to fill, if it needs to be filled try using a carpentry putty or 2-component. Alternatively, cut strips to size, glue them in, and then putty/caulk.