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What am I doing wrong on these blocks?!

7K views 26 replies 7 participants last post by  marksson 
#1 ·
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!
 
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#3 ·
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)
 
#4 ·
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.
 
#6 ·
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:
 
#7 ·
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!
 
#11 ·
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.
 
#12 ·
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.
 
#13 ·
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.
 
#14 ·
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.
 
#15 ·
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
 
#16 ·
I don't know where anywhere in the area is where I can find reputable advice. I've got soo many projects going at once here (first home, and intentionally a fixer-upper), that I've found sourcing out help at more 'professional' places is a waste. Maybe it's because I'm down in FL, but I'm born/raised in the northeast and just got here, maybe I project something wrong. Bottom line is I get crap help / rapport no matter where I seem to go here, not at all like up north. I'm sure it's just the new area.

Anyways, as far as this goes, I'm just gonna try it out on the wall with the bonding agent. I used the pressure washer to make the back of my house 3 separate 'zones':
1) old stucco still on, primer and everything (with spalling pieces chipped off)
2) pressure washed to primer only, no more stucco
3) pressure washed all the way to clean block.


I'm going to use the lanco liquid bonding agent and attempt to do a base coat on all 3 sections, to see how they hold after a few days (thanks whoever recommended that, I know it's common sense lol, but sometimes you have so much going on at once you can't think straight to save your life). If they hold good on all 3, i'm just gonna pressure wash off the spots where the old stucco is spalling/cracking, and just go over it all with the bonding agent, then stucco.


Oh, I should add that I did call lanco, and their rep (the 'chemist' the receptionist told me :wink: ) told me it'd hold just fine, and that I could bond stucco to nearly any sound substrate with their product.

As expensive as the stuff is, I'm considering using it as an admixture directly in my stucco as well (base coat only), but unsure, as my amerimix stucco supposedly already is 'fortified', so I don't want to cause problems.
 
#17 ·
When you shop at a material supply house, as a rule, you will be expected to know what you WANT, as opposed to knowing only what you want to DO.

Do your research (like it appears you have), and then hit the supply houses. They will be able to help you a lot more if they are explaining dry times on Lanco Red Bond VS explaining what bonding agent is.

It sounds like you have it well in hand, anyway.
 
#18 ·
When you shop at a material supply house, as a rule, you will be expected to know what you WANT, as opposed to knowing only what you want to DO.

Do your research (like it appears you have), and then hit the supply houses. They will be able to help you a lot more if they are explaining dry times on Lanco Red Bond VS explaining what bonding agent is.

It sounds like you have it well in hand, anyway.
Thanks, I hope I do anyways!

Yeah that's what I did, when we got the house under contract, I had about 100 pictures of every detail of the property. During the ~1month period before closing, I was online / library for all of my renovations. I've read 'how to stucco' instructions from a minimum of 10 sources (probably closer to 20). So it's not that I don't understand the application, it's just that when I hit a little snag, I have no idea what it is or how to get around it. Like, if the blocks were new and had nothing on them, I would've been all set. I figured I could just pressure blast them back to normal, but that didn't work. So then it's trouble shooting on something that I only know how to do in general terms. I know the basics for how to do a 3 step application over lathe, I know how to do a 2 step application over block, but when I hit a snag like this, I'm goddamned clueless haha.

I'll be testing those sections tomorrow (or the day after - may have gotten a little too much sun today!). I'll post pics as it progresses, I've noticed the pictures section of this site doesn't seem to get much love. I'm planning to change that! I'll be posting all my projects (for advice, tips, etc) while doing this renovation, but when done will be posting all the pics (probably before/after style). This house was bought at a great price, but is severely outdated. Luckily, it's layout, structure, location, etc are all great, but it just needs tons of TLC. I'm devoting myself (as is my brother) to the renovation, so it should be coming along pretty quickly. When done (hopefully within a month or two), I'll have done:
- full landscaping overhaul, new palms, new turf, etc
- refinished cement slabs (garage, out back, driveway, front stoop), mostly done with tan (some will be tan overlays, uniform color), while some will be tan stains (probably on overlays, unsure so far)
- vinyl siding removed, replaced with stucco
- bedrooms totally redone (this is already complete, they were tiled, repainted, etc)
- refinished garage
- lightly remodeled bathroom


Those are the 'major' projects, and a ton of other things (like replacing every piece of old school gold in the house, I've got a box out in the garage of stainless steel knobs, hinges, etc, and new electrical plates, etc). In the end, the place will look totally different.

I'm glad this forum is here, because this is my first attempt at this kind of thing, but it's something I want to learn and keep doing, and you guys are great for helping wiht problems encountered such as this one. When it's done, this place should be night/day compared to when we bought it.
 
#19 ·
Began today, I did this wall (see pic). I did it because it had some spots all bare down to concrete, some spots that were just the old primer, and some spots that were primer + spray-on-stucco. I figured I'll wait a few days, check it out, and see if the thing held up nicely.

I applied the lanco, waited 2 hrs, then applied. I misted it several times since, and now have it tarped for the night to keep it from drying out.

Any ideas on how to tell if it is good? My guess is that none will fall off the wall. Surely if I try, I could get it all off, because I'm strong lol. How do I know if it's a satisfactory bond? wait a few days and give it a firm bang, maybe something like that? I guess that, since I've never been around this stuff, I don't know how it *should* feel after a few days, so I won't know if it's too strong or too weak of a bond.
 

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#22 ·
premixed. It's 'amerimix stucco', supposedly is fortified, but I've been adding ~1liter of lanco liquid bonding agent to the mud, in addition to coating the wall with the lanco first.

This morning, the wall was still there behind its tent. I misted it again, keeping it strong through the cure.


How long should I be keeping this moist? How long before final coat goes on (no brown coat here, this will be a 2 step application)? I've read everything between 48 hours, 78 hours if hot outside, up to 2 weeks.
 
#25 ·
could you please elaborate, I'm all for doing things the right way the first time. I want to learn to be good at what I'm doing, as I'm planning to do this forever (remodeling, not from a contracting perspective, more from owning properties that I just remodel myself). So far I've got a couple walls up, just base coats, and they seem rock solid. I'm kicking them, trying to pull them off, they seem like they're on there thick and strong.

If you see any flaws, please let me know before I continue along the wrong path. I'm basically just:

- applying lanco liquid bonding agent to the wall (that's been cleaned first)
- letting dry for at least 2 hours, as per instructions (although by then it doesn't even feel tacky any more, but I don't want to go against their instructions
- after 2 hours, I'm mixing up 2 bags of stucco in a wheel barrow, mixing very thoroughly, I'm almost positive i've got my slump where it needs to be, and am adding in some of the bonding agent to the mud as well
- applying this to 1 wall section at a time
- lightly misting the wall about 2 or 3 times daily
(oh, should've mentioned that the wall gets tarped pretty tightly right after application, I pull the tarp back to mist it daily. I do that for about 3 days after original application).


If you see somethign wrong with my approach, please let me know. I can post some pics of the sections I've done if it would help in the least
 
#26 ·
Some bonding agents will re-emulsify once only. That means they dry out, then when when wetted become soft again. Some bonding agents will re-emulsify until the reaction is complete (several wet/dry cycles). Those are generally fine for most wall applications and flatwork, but are not suitable for water submersion.

FYI.
 
#27 ·
Joeboy
I was kind of joking.
Although I would point out that you just need to follow the manufacturers instructions to the letter and not add your own thoughts/ideas/improvements to their instructions.
If you do, you may affect their product liability.
letting dry for at least 2 hours, as per instructions (although by then it doesn't even feel tacky any more, but I don't want to go against their instructions
at least 2hours
If it's not tacky then leave it a little longer.
Otherwise sounds like it is to the letter.
:thumbup:
 
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