Basement cinder block fine power efflorescence like

1950 Basement cinder block foundation, Has been treated with several coats of different types of paint, but still comes back a salty powder efflorescence like.

Could any or all of your experience eyes take a shot to find an explanation? All inputs are welcome…!

Note that the outside grading is running away from foundations. All vegetation is kept over 3 feet away from the building. Current exterior stormwater management is favorable.

Very common in my area. May or may not be evidence of a larger moisture problem. Grade is not the only solution or cause of moisture issues.

Edit: I will note, the dark staining pushing thru is a bit concerning for it may indicate water intrusion.


Concrete and masonry have a lot of minerals and moisture brings them to the surface. As Brian says, lots of reason for the moisture.

That is irrelevant.
As long as there is soil contact with the wall, moisture will wick into the wall IF THERE IS AN IMPROPER MOISTURE BARRIER present to prevent it from occurring!!


Concrete block is fairly porous, a coat of paint doesn’t stop that (especially if it’s on the inside). Your pictures show a fairly minor efflorescence. something like this is a little more concerning.


Here is an upper part of a wall with a similar issue. Roof problems along the roof edge has caused CMU block saturation. Look closely at the top of the door frame, water is seeping in from the block above.


The theoretical limit of capillary rise in concrete is about 10 kilometers —and folks that is not a typo—it really is about 10 kilometers or about 6 miles. Concrete sucks big time. In wood it is about 400 feet—the height limit trees can grow to is set by the size of the capillary pores in wood.


That interior treatment will never work.
You could dry wire brushing all the paint off one CMU block, and see if that one drying out
keeps the rest of the blocks dry enough that the paint holds.


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I often consider efflorescence a possible precursor. Some can be tolerated or expected in different environments. Here is a photo of a section of wall below grade. The moisture barrier/foundation drainage has failed. I see similarities in your photo…but they just keep painting over it.



Water Repellency Tests for Concrete Masonry Units.

Evaluating the water repellent characteristics of concrete masonry units is important to ensure that the proper level of protection is provided from the weather in certain applications. NCMA TEK Note 19-7 provides specification information on the required performance of water repellent CMU, and several industry-developed tests methods are referenced. These three tests methods are:

Test Method CMU-WR1 contains standard tests methods for water stream and water droplet tests of concrete masonry units. The purpose of these tests is to visually assess the water absorbency characteristics of the exposed surfaces of a hollow or solid concrete masonry unit when subjected to either a dynamically or statically applied source of water. This test is intended to be quick field check on repellency, and if questionable results are obtained additional laboratory testing is required.

Test Method CMU-WR2 contains the spray bar test method for concrete masonry units. The purpose of this test is to visually assess the migration of water through the exposed surfaces of a hollow or solid concrete masonry unit when multiple streams of water are applied to its outer face for an extended period of time. This test is intended to be performed in a testing laboratory.

Test Method CMU-WR3 contains the test method for assessing water uptake potential of concrete masonry units. The purpose of this test is to evaluate the resistance of a concrete masonry unit to vertical moisture migration due to capillary action, a migration often referred to as wicking or water uptake. This test is intended to be performed in a testing laboratory.

Nice pic, Brain. Scotts as well.
The idea is to never paint foundations, no matter the material they are/where constructed from.

Moisture has to evaporate. Any signs of interior foundation efflorescence is a signal that the perimeter drainage field and weep tiles are under preforming. Its time for exterior foundation lot maintenance, including gutters and downspout relocation if/when applicable.


There is one very important question you must ask your foundation waterproofing contractor when hiring him to repair intrusion like this. if you want a repair that will last. “Do you own a backhoe”. If not, send him packing.


Or… “How many crew members with shovels” will I be paying for??


From a house last week. Improper flashing around the chimney was concealed with a cover flashing. Moisture was detected around the fireplace on the living room ceiling. Homeowner claims everything has been fixed there’s nothing to be concerned with. This isn’t the worst part of the foundation. This leak has been going on for a long time.


That’s an interesting photo Martin starting with the stack bond technique. Then the patches or repairs. The exposed corner illustrates a minimal footer. Finally the moisture. A lot going on there. Interestingly, it’s still standing.

I agree the CMU’s appear to be just resting on the soil. I did not see a concrete pad for any of them. The other side of the foundation exhibited signs of thick mortar patching at the base of the brick foundation. Of course I was unable to determine the condition of that portion of the brick foundation because it has been concealed.

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The other side of the house.


I’ll take #2 and #4. Yeah you don’t need a ladder to inspect roofs :rofl: