Cracks, Why?

[Dion Battles]

I would like to know why I had these cracks appear. I sprayed the scratch coat with water, it is not very thick, and it is the TruPac mix. I am looking forward to hearing what you have to say and any ideas that you guys have to fix it. Is there a slurry or cream that I can mix the will fill them without affecting the texture? Thank you everyone for your responce.

[Nathan Giffin Vertical Artisans]

This is a common problem but can be avoided.

Carving mixes are generally designed to be carving mixes not "overlay" they are designed to be applied with a thickness of 1.5" to 3" and then sculpted. However, when these mixes are applied in very thin applications, there are issues with hair line cracks.

My suspicions are that the scratch coat is drawing moisture from the backside and air from the front side of the mix. This is an accelerated evaporation. Hairline cracks with occur.

There are a few ways that I deal with this issue.

Number one I don't use a carving mix for very thin applications 1/4" to 3/4" ...it wasn't designed for it.
Number two if I have to use the carving mix in a pinch, I will pre dampen the scratch coat to avoid accelerated evaporation.
Number three I will use ( Original 19 ) from Specco industries to gel the water in the mix thus stopping the evaporation even more.

To correct the problem I would just take some mix and make a puddy like constancy and rub in the hair line cracks before you stain the project.

There is more I can say but time doesn't allow it right now.

Hope this helps.

[Nathan Brownell]

I have done several jobs with tru pacs and done thin coats without any issues. Maybe in part to using a primer on the surface over the scratch coat. Keep the water content a little lower than normal. I am not the pro!! Maybe Nathan can shed more light on using primer and if this would help with the scratch coat from sucking to much moisture from the face coat. Nathan, I would like to hear more on suggestions for a thin coat texture material if you care to shed light on this. Stucco material ? I would like to avoid any issues in the future.

[Tru Pac/Walttools/Don]

Sorry Dion that you have come across this dreaded issue. The previous feedback is correct. Thin applications in any mix can be an issue at times. In those cases the scratch coat needs to be pretty wet, or as suggested, you can use a primer, though make sure the primer is not fully cured before application of the carving mix. If the primer is cured, you have basically succeeded in "sealing" your scratchcoat providing you with the more frustrating - perpetual delamination syndrome. Just check with the information about your primer to verify the cure times. Also, the scratchcoat itself can make a big difference. A very porous, super rough coat will really wick the moisture from your carvable faster than a bit smoother, less profiled coat. Keep in mind if you are going thin on top you will not need to be so aggressive with the scratchcoat. Lastly, one can also fortify the scratchcoat mix which will not only increase the integrity of the surface but will reduce the absorption rate of the moisture from the carving mix once applied. Or sometimes, no matter what, it just happens....
Sorry to be long winded.
Don

[Dion Battles]

Thank you all for your knowledge on this. I plan on doing more concrete "wood", so which is better, change the mix I use when I aam doing wood projects like this or just do what you guys sudgested above?

[Tru Pac/Walttools/Don]

The answer could be both. You may find that by tweaking your process a bit, the mix will be fine. If not, then I would suggest changing over to a "non" vertical mix if you keep it at about 5/8 or so. Working time will be cut down a bit but the woodgraining process can be fairly quick anyway so time should not be an issue. Stay in touch.

Dion Battles said:

Thank you all for your knowledge on this. I plan on doing more concrete "wood", so which is better, change the mix I use when I aam doing wood projects like this or just do what you guys sudgested above?

[Nathan Brownell]

Very good point about the scratch coat Don. Overlloked that one. I do not use a rake for the scratch coat when applying thin texture. I simply will take the edge of the trowel and create some scratch marks.

Don/Walttools said:

Sorry Dion that you have come across this dreaded issue. The previous feedback is correct. Thin applications in any mix can be an issue at times. In those cases the scratch coat needs to be pretty wet, or as suggested, you can use a primer, though make sure the primer is not fully cured before application of the carving mix. If the primer is cured, you have basically succeeded in "sealing" your scratchcoat providing you with the more frustrating - perpetual delamination syndrome. Just check with the information about your primer to verify the cure times. Also, the scratchcoat itself can make a big difference. A very porous, super rough coat will really wick the moisture from your carvable faster than a bit smoother, less profiled coat. Keep in mind if you are going thin on top you will not need to be so aggressive with the scratchcoat. Lastly, one can also fortify the scratchcoat mix which will not only increase the integrity of the surface but will reduce the absorption rate of the moisture from the carving mix once applied. Or sometimes, no matter what, it just happens....
Sorry to be long winded.
Don

[Dion Battles]

Don

What tweaking do you suggest? And couldnt a guy just use a masonary cement for wood textures like this? You are right, texturing wood is a quick process.

Thanks

Dion

Don/Walttools said:

The answer could be both. You may find that by tweaking your process a bit, the mix will be fine. If not, then I would suggest changing over to a "non" vertical mix if you keep it at about 5/8 or so. Working time will be cut down a bit but the woodgraining process can be fairly quick anyway so time should not be an issue. Stay in touch.

Dion Battles said:

Thank you all for your knowledge on this. I plan on doing more concrete "wood", so which is better, change the mix I use when I aam doing wood projects like this or just do what you guys sudgested above?

[Tru Pac/Walttools/Don]

The tweaking refers to making sure the scatchcoat is proper for what you are doing, in this case the wood graining.in order to prevent as a rapid a dryout as you have had. A light prime will help with the moisture retention. Masonry cement as an overlayment will not be so good. It may end up like a dry river bed when you are through. Really, the best choice if you are purely graining would be to use an standard overlayment mix and Nate had mentioned. It is made for thin applications, many are designed to take texture, will actually offer a finer finish and structurally will offer more integrity. Jody may be able to chime in on this as well.

[Jody Smith]

Dion on the thin areas like the wood graining of a door I would use nothing but an overlay mix. When facing a door I would remove it to create the wood grain horizontal only if you are stamping or texture rolling it though. If you are going to carve the texture then I would leave it hanging so that the carve debris fall to the floor and out of your way. The overlays dry quicker so once you trowel be ready to apply your textures. I have created many fountains with the wood grain spillways. I went through board after board and mix after mix to fight the cracking it wasn’t the mix it was the process and material I was using. I went to a concrete overlay mix and the problem stopped, I have to stress that everything needs to be in place so that you get the timing right for the texturing. Most overlays have retarders and accelerators as well to customize your dry times. The overlays have more flexibility and a door needs that, I trowel it to ¼”. I use the overlays in all of the water areas on the standup fountains due to the non-porous properties that most overlays have. Trust me it will stick I once painted glass with mastic and applied the overlay and it locked on solid. The Tru-Pac was great for me and I applied it at around 1.5” to 2” and I had no cracking. I look forward to carving more with it in the future. Please let me know how the overlay mix works for you I think this will help you out. Good luck with the wood graining and I can’t wait to see some new pictures of your work. Don great job on staying with this issue and helping Dion find the perfect mix for his application. This is why I love this forum the artisans knowledge is endless. I owe so much to this forum and the first class artisans that inspire me everyday.



Don/Walttools said:

The tweaking refers to making sure the scatchcoat is proper for what you are doing, in this case the wood graining.in order to prevent as a rapid a dryout as you have had. A light prime will help with the moisture retention. Masonry cement as an overlayment will not be so good. It may end up like a dry river bed when you are through. Really, the best choice if you are purely graining would be to use an standard overlayment mix and Nate had mentioned. It is made for thin applications, many are designed to take texture, will actually offer a finer finish and structurally will offer more integrity. Jody may be able to chime in on this as well.

[Dion Battles]

Wow, I cannot believe the indepth answers I get here. Thank you all for treating me and my questions, like yjey mean something. I really do respect you all for that. Thanks again!

I will try the overlayment mix for "vertical wood", I have used it for floors, I guess I just need to use my brain and think outside the box a lttle bit. Thanks for opening my eyes.

Dion

[Paul]

So would an overlay be recommend for a shower surround? Is there an available overlay mix in white?

-Paul

[Lee Woolsey]

Concrete Coatings Inc makes a stampable overlay in both white and gray mixes (http://concretecoatingsinc.com/stamp_tek_stampable_overlay.html). It has fiber in the mix and feels kind of granular, but it holds texture well and works pretty well in shower applications. We made a great barn-wood sample for our last home show display with it. (You have to use a VAE primer or it'll delaminate -- http://concretecoatingsinc.com/duraset-vae.html )

 

All the other showers I do, have either used their G-100 grout & modifier or Tru-Pak.