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sealing a cinder block wall

I just finished sealing the cinder block wall in our basement with Baer waterproofing paint. After the first coat I noticed little orange rust colored spots in one corner of the room. Nice fresh white coat of paint, little spots the size of peas on one wall.  What is causing it?  Also there are some large creases that need to be filled. Other than cement, is there a product that I can use to simply fill the cracks?, then paint over them.

Please advise...

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Posted 2011-03-15T02:16:34+0000  by Rob13 Rob13

Good Morning Rob13,


It's a great day in the Paint Department!


I created this video to show you the products you can use to seal the cracks in your cinder block wall.




Three of the products are designed to simply fill the crack in your wall, but only the fourth will hold back hydrostatic pressure (water from outside coming through the wall).


All four are paintable, but remember to use an oil-based primer if you choose the PL Concrete Crack Sealant because it contains mineral spirits. The other simple crack fillers, DAP Concrete Caulk and Quickrete in a caulk tube, are water-based and can be primed and painted with water-based products.


Should you have hydrostatic pressure, you will need to use DryLok Fast Plug to stop the leak. Fast Plug is a Hydraulic Cement that works best if you open the seam into an inverted V-channel and then trowel it into the channel. The mixed product expands to fill the channel and seals active water flow through the wall.


The Behr Waterproofing Paint you already purchased will cover all four of these products.


Others in the Community may be pleased to learn that Behr's Waterproofing Paint is tintable into several light colors. A color chart is located next the product in the Paint Department.


Finally, I noticed that SteelToes was helping you yesterday and I am including a link to his thread.


If you have excessive moisture in that area, you will likely need to kill both mold and mildew to ensure proper adhesion of your paint. Follow up if this is one of your issues and one of us can assist you further.


I hope this helps!

Posted 2011-03-15T14:12:02+0000  by Pat_HD_ATL

I recently had a thirty year old porch replaced on my house.  The original cinder blocks had crumbled, and no longer were supporting the concrete pad adequately.  I am still not sure what cause the blocks to crumble, but I'm hoping that by applying a sealant, or some type of weather protection on the new cinder block walls will keep this from happening in the future.


Can you suggest a sealant or protection that can be applied to the cinder blocks?  I look forward to your reply.

Posted 2012-06-12T19:35:48+0000  by shoebridge

Hello ShoeBridge!


In the video and written thread above, we discussed Behr Basement and Masonry paint. Behr Basement and Masonry Paint.jpg


This product is simple to apply, will protect your new block. and can be ordered in several off-white and light colors at The Paint Pit.


If your block is exposed to active groundwater, you'll want to use a product labeled for hydrostatic pressure. Behr Basement and Masonry paint will withstand up to 10 lb. of hydrostatic pressure. Hydrostatic paint is also discussed in the video.


APPLICATION: Expect to use a stiff nylon bristle brush and a 1/2 nap or 3/4 nap roller to apply these product. Follow dry-time instructions before applying your second coat.

Posted 2012-06-14T14:49:13+0000  by Pat_HD_ATL

Hey Pat.  I was just googling and found this, big help.


I don't think I have any hydrostatic pressur in my home (although, I can't be sure of that, any way to tell?).


With that said, I was looking at one of the 3 easier solutions in a tube to fill my cracks and prevent any leaks during a hard rain.  You mention The other simple crack fillers like DAP Concrete Caulk and Quickrete in a caulk tube.


Can you describe the difference between the 3 you mention on there?  Is one better than the other for any reason?



Posted 2012-09-29T12:19:27+0000  by shackrock

Thanks for the follow-up question Shackrock!


I love it when people find my posts on Google!


Glad the video was helpful as well!


Hydraulic cement is unique because it expands as it dries and will stop active foundation leaks. It is powder you mix with water. When the word "hydraulic" appears on the product label, this is the indicator that it will stop the flow of pressurized water.


The three caulk tube concrete crack fillers are not hydraulic ... they fill cracks and will prevent the flow of passive water, but are not designed to hold back hydrostatic pressure or ground-water pushing up from beneath the foundation.


DAP Concrete Caulk: water-based


PL Concrete Crack and Masonry Sealant: solvent-based


Quikrete Mortar Repair: ready-mix Quikrete concrete in a caulk tube


Click the hyperlinks for product specifications.

Posted 2012-10-02T14:29:07+0000  by Pat_HD_ATL



I have a downstairs room that has been leaking for a while. I tore out the original drywall and removed the damaged furring strips. I tried to paint the wall with the UGL sealer. I guess the walls were way to wet because the sealer just ran right off the walls. I am trying to dry out the walls and try again. I placed a small heater with a blower against the wall and it seams to be getting worse. I thought about getting some of the masonary waterproofing cement from Home Depot to help seal it. I am at a loss of really what to do. Any ideas?

Posted 2012-11-19T14:52:31+0000  by Nick106

Hello Nick106!


Every room in your home has relatively higher or lower humidity depending upon temperature, air flow, moisture sources, and a variety of other factors.


Based upon your description, I suspect the relative humidity in your basement is very high.


My guess is there is very little air flow and the moisture you evaporate with your heater is simply re-condensing on the cool surface of the basement wall.


I would suggest several steps:

1) Add additional heat sources to increase the rate of evaporation;

2) Add one or more fans that cross-ventilate the basement and pulls the humidity out of your home as it draws fresh air inside; or

3) Add a de-humidifier that will reduce the relative humidity in the basement below forty-five percent.


Of these options, the most rapid will be the combination of numbers 1 and 2.


The de-humidifier will be effective in both the short-run and long-run, but will require a longer time to initially reduce the humidity in your basement. You will also need to regularly drain the de-humidifier or place the gravity-feed drain tube into an existing drain in your basement floor.


NOTE: Even though both products suggest they can be applied over slightly damp surfaces, your best bet is to remove the moisture from the room before proceeding. This will give your water-based coating a chance to dry properly and ultimately seal the wall.

Posted 2012-11-20T15:47:07+0000  by Pat_HD_ATL

Hello, am enjoying this conversation because I have a very old block building that when it rains water leaks inside.  I discovered that long time ago the windows were blocked with a poor job done and they have a lip at the bottom.  Someone tried to seal the seam between the lip and the now blocked window with cement mix but when it rains water permeates and leak inside.  I already painted the outer wall but would like to seal these old blocked windows.  Another option will be to re-open some windows and leave others blocked for security reasons.  I still need something to help seal the ones I will leave blocked, and I can re-paint them afterwards.  This is needed on the outer wall.  

Posted 2013-06-11T16:58:36+0000  by salsacola

Thanks for picking up the thread salsacola!


Your Old House is just a step away from a solid seal that will not leak.


If a gap exists or if you can create a gap, the hydraulic cement can be mixed and troweled into the seam. Once dry, you could paint with Behr Concrete Waterproofing.





You could tape the existing seams and windows and use one of the new spray sealants.


Leak Stop and NeverWet from Rust-Oleum are both great products to waterproof existing materials with only a small amount of effort.


You might try the simple approach and if you still see a leak, then apply the next level of effort.

Posted 2013-06-11T17:47:53+0000  by Pat_HD_ATL



Our bulkhead sits on a row of cinderblocks atop a concrete foundation, and this fall we brought in some loam to level and reseed the back yard.  When we did that, the seam went from being above grade to level with the grade, and after a snow-turned-to-rain storm yesterday and last night, I had a minor flood in the basement.  What do you think my best course of action is? It woldn't take much to dig around the bulkhead foundation to apply something on the outside, but we're on Cape Cod, and in addition to snow, rain and puddling, temperatures this time of year seem to average anywhere from 20's to 40's, so I'd need something I can use in those temps.  Time is also of the essence because my wife and I have twins on the way any day now, and I'm in the middle of a pretty big bathroom floor repair...What do you think?  Thank you

Posted 2013-12-16T03:35:22+0000  by mmccar
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