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DebbieG 09-02-2010 08:37 PM

Staining cinderblock sides of raised concrete slab patio
2 Attachment(s)
Hi all...Need a professional opinion....I recently had sagging slab removed from existing raised concrete patio built on cinderblock. (See attached photos)..It was replaced w/a colored/stamped concrete slab. The top course of cinderblocks was replaced but the lower old ones were left in place to save $$.
The old top used to sag toward house and rain would puddle outside of doorwall so we would sweep it off onto the driveway and it would stay against the block until it dried for awhile. (That part of the driveway has also been replaced to drain away).
Problem now is we would like to stain the cinderblock to match the stamped top but the side where we used to sweep the water off has some blackened blocks (see photo)..There are a few other areas where the blocks are darker also. We had talked to the contractor who did the new work about staining the cinderblock to match the new slab and he recommended we go to Sherwin Williams. I asked the Sherwin Williams guy what the best type would be and if we should use a type that seals the block, or one that allows it to still breathe since water can still come up though the ground and will try to escape through the block...(I'm thinking that sealing it may hold all moisture and water in and that might not be a good thing)....He just said "thats a good question... I don't know the answer to that one". ??
I can't seem to find anything about it online either.
He recommended starting out scrubbing it with Dawn dish detergent and powerwasing to get the black off no matter what we used after. I did that but it hardly removed anything. I also tied a 50/50 mixture of bleach/water on the black parts but that did nothing either. Im afraid to use anything more powerful because it will be rinsing down onto new ground level slab and I don't want to risk it ruining the sealer on that.
Im now to the point in thinking that, if I can't get the black off, I'm going to have to go with a very dark brown instead of a matching color just to hide it.
I'm hoping to get a professional opinion on:
A. Do we need to use a special type of stain so that concrete can still breathe and release moisture or is it ok to seal it?
B. Is there something I can use to remove the black without worrying about it ruining the sealer on the lower part as it runs down or when I rinse it off?
(While I'm at it....I will be building a Pergola over the top soon too. Any advice on the best brackets to use the keep moisture from wicking up into the post? Home Depots weren't raised to prevent this)?
Thanks !

mudmixer 09-02-2010 09:21 PM

You are going to have to cover up the mistake of using two different products in a visually critical situation.

You use the term "cinder block" when they are probably not those and were just two different concrete block of different ages that were purchased at much different times and sources and subjected to different condition due to the different properties and exposures.


DebbieG 09-05-2010 06:39 AM bad?....That being said I still have the same questions? Should I use a sealing type concrete stain that will trap moisture within or find one that allows the block to breathe so moisture can escape? there something I can use to clean the black off of the blocks without worrying about it being rinsed onto the lower part of patio and ruining the sheen of the sealer?

CSmith 09-05-2010 10:59 AM

Hi Debbie you want a breathable stain.

After pressure washing and scrubbing unfortunately no, your bottom course is stained. To lighten that up would take some heavy duty chemicals which is not an option at this point, it would kill your new patio. If it were, you probably would never get them looking the same anyway for the reasons that Dick stated.

If your dead set on a lighter, semi transparent stain there is another option but probably out side of most DIYers wheelhouse but worth mentioning is a portland stucco plaster. The materials are cheap and you can create any texture you want, after it cures you can stain it. You could also use color dye in the mix but thats much harder and takes some experience to color match.


erndog 09-05-2010 04:02 PM

stucco it
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Hi I am just an amateur( so take my advice with a grain) but I feel if you just stain the block you will still see the grid pattern of the blocks. I put up a retaining wall and slapped a product called quikwall on it. I put in a stain that also came from HD. I think mine came out nice, so it might be an option for you. Good luck and the stamped concrete looks great.

DebbieG 09-06-2010 10:04 AM

Thanks guys! I have been considering the stucco from day 1 and may just go back to that because I too wasn't sure if I really wanted to see the mortar lines of the block anymore or not so we waited to see the finished top to decide.
Also, we were thinking that if we didn't like how it turned out after staining, we could go this route to cover it and start over. (not sure if you can stucco over a stained surface yet though).

CSmith - I don't think the Portland stucco plaster is outside of my abilities and I guess as far as color matching...I can show the colors that were chosen for the patio for some help on that and if it doesn't turn out well, I can just darken more for contrast. Do I have to find a concrete supplier for this product or is it at HD or Lowes?
(ps..Do u do this for a living?)

Also, if I was right in thinking that the block still needs to breathe, which is the better material for the job...the Portland Stucco or the Quickwall that "erndog" mentioned? Also, will these products just adhere to the block or do I have to put up some mesh first?
Thanks again!

erndog 09-06-2010 11:22 AM

quikwall info
Hi the quikwall is from home depot. It is designed to adhere directly on block. It's made to be the only support for wall, you just drystack the block and apply this over the top. But it will work for you, there are fibers in it which some stick out when you're done but they wear off after a while. I just used the concrete stain that HD sells, I believe it was "buff".

CSmith 09-06-2010 04:44 PM

Yes I do, I specialize in brick/ block construction and restoration.

QuickWall is a type of portland stucco which would work fine. However I’ve never used QW I batch my own and can't comment on how the fibers would affect the finish, might be a little hairy. The fibers added to QW are for flexural strength needed for drystack mortarless walls like erndog built. The plus side of QW or something similar in a bag it will save you the trouble of having to batch your own stucco and buying all the components separately. You just pair it with there fortifier admixture

If you give QW a go do a test spot in an inconspicious area or on a leftover block to make sure you like the texture it may or may not bother you if it is a little hairy

Lastly read the directions and follow there recommendations for things like coat depth. You don’t want apply a coat to thick at one time or it will promote cracking. The walls must be clean and you want to apply your stucco to a dampened wall(not wet). This prevents the block from sucking to much moisture out of the stucco insuring a proper cure.


DebbieG 09-10-2010 06:19 PM

Thanks to both of you. Erndog, your wall looks great...I guess the fibers shouldn't be that noticeable unless you get up close so I'd be ok with that...especially if they wear off.
CSmith...thanks for your if I use this quickwall, it will still allow the patio to breath as long as I can find a stain that doesn't seal?
Glad I even asked that because the guy at Sherwin Williams was ready to sell me a sealer and I try to make sure to bow to the experts on things like this.

DebbieG 09-10-2010 06:22 PM

Oops....forgot to ask one more thing....if we were to go ahead and stain it as is, and still didn't like still being able to see the outlines of the block, could we use this stuff over top of that?
Thanks again

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