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-   -   What am I doing wrong on these blocks?! (http://www.diychatroom.com/f19/what-am-i-doing-wrong-these-blocks-8627/)

joeyboy 05-22-2007 07:54 PM

What am I doing wrong on these blocks?!
 
Well, today I began what I thought would be a smooth stucco job (lol). The house is concrete block, which they primed and then did that 1 step stucco stuff (spray on stucco).

So, I go to home depot, rent the power washer (3500psi) to get this stuff off. I spent all day out in the yard trying to blast this stuff off my house to get clean blocks, and I literally only got maybe 30-40 sq. ft. of the primer off my house.

The one step stucco stuff flies off, even when the pressure washer is a foot away from the wall. But this white sealer/primer/whatever, it needs to have 3500psi held half an inch away for a couple seconds to come off.



There has to be another way, I'm gonna flood the neighborhood doing the whole house this way.

Can I just use my bonding agent over the existing primer (it's "lanco liquid bonding agent")?

Should I be using another kind of power tool? Sand blaster?


I can go snap some pics if needed, but it's nothing unique, it just looks like white paint, only it's adhered to teh blocks like gorilla glue!

Tscarborough 05-22-2007 09:36 PM

I don't understand. Why are you blasting off what you have already done?

joeyboy 05-23-2007 11:19 AM

I'm not, I'm preparing for my stucco by removing the previous, old stucco on the house. The original siding on the concrete blocks is this reaaaaaly thin spray on stucco stuff, but the primer they used on the blocks before applying it won't come off. I need to remove everything back to bare block before applying stucco to the blocks, to ensure my stucco adheres properly (i'm doing a 2 coat application directly onto block. I can remove their 'stucco' spray on stuff fine, but the primer they used before it is insanely hard to get off. It's almost like I need to blast 1/16" off the concrete itself)

joeyboy 05-23-2007 11:21 AM

Basically it's just a coat of primer that I'm worried about, it's been on my concrete blocks for god knows how long. Pressure washing it off is pointless, hand chiseling is also pretty futile, I don't know if I should be using another method to remove it (chemicals, sandblasting, etc), or if maybe I should just put my bonding primer ("lanco bonding agent") directly on the old bonding primer.

concretemasonry 05-23-2007 11:26 AM

If the existing coat of primer is working well and is so hard to remove why not go over it with a compatible material?

joeyboy 05-23-2007 01:47 PM

YES!!!!

That's what the guy at home depot just said to me, but I'd never go on just 1 opinion (because if i did and it was wrong, I'd do things that would have me forever banned from home depot lol).

Great, that's very good to know, wish I didn't just bring their pressure washer back now lol!

Guess I'll keep chiseling off the stucco, maybe go back and rent the damn thing again :laughing:

joeyboy 05-23-2007 01:49 PM

I had thought that, I just was afraid that when I apply my bonding agent to it, maybe the bonding agent wouldn't adhere properly to the old primer, and then my stucco would fall off.


Just to make sure I have this right:

1) power wash / chip off the old, thin 1/16'' stucco spray on stuff
2) wall is then pure white blocks, white from the old layer of primer
3) roll on my primer (lanco liquid bonding agent)
4) wait at least 2 hrs, but not more than 24 hrs, after applying the primer to start my scratch coat

Is that pretty much on point?



Thanks again for your responses!

J187 05-23-2007 01:54 PM

Quote:

Originally Posted by concretemasonry (Post 46004)
If the existing coat of primer is working well and is so hard to remove why not go over it with a compatible material?



Quote:

Originally Posted by joeyboy (Post 46014)
That's what the guy at home depot just said to me


Hmm, ConcreteMasonry, maybe you want to rethink your suggestion....:biggrin:

marksson 05-23-2007 03:21 PM

joeyboy
I would contact the manufacturer of your new primer as a first point of contact, because without their ok they will not warranty their product.

marksson 05-23-2007 03:23 PM

Having said that, if they are not ok with it and the original primer is sticking like s#*t to a shovel then I would go with it anyway.

joeyboy 05-23-2007 04:19 PM

Thanks a lot, I'm glad I've gotten confirmation because I didn't know how on earth I was gonna be able to get that stuff off. I'll call them, I'm guessing they'll be hesitant since it's not concrete, and wouldn't want to take the chance okaying something that may not work (even if it's entirely likely to). I'll call them to see what they have to say.

concretemasonry 05-23-2007 05:01 PM

J187 -

I thought before I made my suggestion based on experience. In fact, I have thought about it for 30 years or so. I also assumed he had the preparation and application instructions from the product (lanco) he planned to use.

Stucco and concrete are very similar materials with the same chemistry and only a difference in the aggregate size and the application method.

Spray stucco bonds very well (perhaps too well in some cases) to concrete/concrete block because they are compatible materials. If you cannot remove one cement based product from another with reasonable means you must assume there is a satisfactory bond.

It not like non-similar materials (paints, paint-type waterproofers) where vapor transmission is an additional factor.

joeyboy 05-23-2007 06:56 PM

Quote:

Originally Posted by concretemasonry (Post 46036)
Spray stucco bonds very well (perhaps too well in some cases) to concrete/concrete block because they are compatible materials. If you cannot remove one cement based product from another with reasonable means you must assume there is a satisfactory bond.

I do not believe it is a masonry product that I'm dealing with, I believe it's solely a primer, not unlike my 'lanco concrete bonding agent'. The spray on stucco stuff comes off just fine, it's the white primer/bonding agent that's stuck to the blocks, which I didn't think was cement based.

Tscarborough 05-23-2007 09:04 PM

As a rule, a bonding agent is very close to a bond-breaking agent. As you note from your lanco instructions, you must apply before 24 hours (too long, in my opinion, the sweet spot is 2-4 hours, depending upon weather). If you don't, then you will have applied a bondbreaker to the surface.

It is very simple to test: Mix a small amount of what you will use for stucco, apply it to the surface, wait 3 days and see how hard it is to knock off.

clasact 05-24-2007 07:06 PM

before I started my stucco project I went to my local masonry/stone place to ask a few questions( I had about the same problem) and they gave me a test kit for free to try out on a section of my brick to see if I needed to take off what the previous owner had on or not but it bonded great so I went ahead and got started.My point is if you got a place like that in your area instead of a box store I sure they can be of more help to you


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