proper prep for epoxy

[socal77]

The slab is a 3000 PSI mix over a 10 mil visqueen vapor barrier. It has a power steel trowel finish & was poured about three months ago. The building was recently finished & I have been shopping for an epoxy coating contractor.

A contractor's recommendation was to apply a moisture barrier coating rather than grinding, since it is new concrete. He said that the moisture barrier coating would provide good adhesion between the concrete & the epoxy. When I expressed concern about not grinding, he said it would leave noticeable swirl marks that would show through. He said that if I wanted a mechanical surface prep that shot blasting would be better than grinding, but was unnecessary.

Does anyone have any insight into these three prep methods they could share?

Thanks!

 

[Shea]

There is no reason to apply a moisture barrier coating over a slab that has a vapor barrier unless you have some other possible moisture issues you haven't shared.

Only a low solids water based epoxy system is going to show swirl marks from a grinder. Did he say what kind of epoxy it is? Plus, shot blasting the surface is going to create a concrete surface profile that is much more rough than grinding. If anything, that is the type of surface than can show through unless a high build epoxy system is used.

What are his credentials?

 

[LegacyIndustrial]

10-4 all of that. Shea is on the money.

 

[socal77]

There is no reason to apply a moisture barrier coating over a slab that has a vapor barrier unless you have some other possible moisture issues you haven't shared.

Only a low solids water based epoxy system is going to show swirl marks from a grinder. Did he say what kind of epoxy it is? Plus, shot blasting the surface is going to create a concrete surface profile that is much more rough than grinding. If anything, that is the type of surface than can show through unless a high build epoxy system is used.

What are his credentials?

There are no moisture issues that I am aware of. The taped-down plastic sheet test did not show any moisture. The moisture barrier coating was being proposed as a substitute for grinding or shot blasting to enhance adhesion, similar to primer.

It was my understanding that the epoxy was 100% solids, but was not specified on the quote.

He is a state licensed contractor.

 

[Garage Flooring]

There are no moisture issues that I am aware of. The taped-down plastic sheet test did not show any moisture. The moisture barrier coating was being proposed as a substitute for grinding or shot blasting to enhance adhesion, similar to primer.

It was my understanding that the epoxy was 100% solids, but was not specified on the quote.

He is a state licensed contractor.

Shea is right on... Just because someone is a licensed contractor does not mean they know how to apply epoxy! Grind, prime and then coat. Even if you do a moisture barrier, grind first.

 

[Lootenny]

Sorry to threadjack, but as my building project is starting, I'm also thinking about floor coatings. Why do you need to grind new concrete?

 

[benwah]

There is tons of information all over the internet about this, but to sum it up:

1. Creates a proper surface profile for the epoxy to adhere to.
2. Removes any sealers, hardeners, or curing compounds
3. Removes latience and contaminants
4. Gives you an even playing field to apply coatings, removes trowel marks and other imperfections.

...basically

 

[socal77]

Shea is right on... Just because someone is a licensed contractor does not mean they know how to apply epoxy! Grind, prime and then coat. Even if you do a moisture barrier, grind first.

Thank you all for the feedback.

Much appreciated!!