Question on Effervescence on basement walls
 

I'm looking at a potential rental property. It has a basement and the concrete walls are very sound with no evidence of any water damage. However, there is some light effervescence on the walls. I'm wondering if this can be sealed, painted, or what is the best course of action as I will use this space for storage but want to clean it up and paint first.

*Efflorescence.

It means some water was penetrating at some point. If the source of water has been addressed (and it sounds like it has) - a muriatic acid scrub should clean it up and then you can paint or do whatever you plan to do with the space.

Lay off the Alka Seltzer.

It could be a single case of short downspouts and too much rain.
Or there might be a natural spring nearby. Should be a record of it with the city.

You can cut out a section of floor, dig a hole, liner and rocks, etc, install a sump pump if the water table every gets too high. That will help.

Grading and a surface water diversion barrier will also help.
I recently took a look at a beautiful wide property right at the end of long steep hill and turn-around. There was literally nowhere for water to continue downhill around the house. Everything funneled right into it. Yikes. A major flood would knock it right on down the hill.

The preferable way to seal it is from the outside and wrapped underneath....as a a giant reverse bathtub.
Most modern building practices do not address this basic flaw in foundation design.

Mom's former basement had continuous water dripping through a stairwell wall on the uphill side...even after weeks without rain. It trashed her new finished basement a couple times and left mold which probably shortened her husband's life. No problems at all from the decades before. There was either a natural spring or a major city pipe break uphill which the city didn't find or want to find. I was hollering and wanted to help. I was told to shut up and butt out. The house finally sold for a few hundred grand less than it was worth imo. It was a tiny little thing but otherwise in very good shape and located in the most expensive/highest-income area in the city. I would have hung onto it. Then my sister starts looking at properties here and they are all twice or quadruple that price. "Oh that's not a problem". Fffffffffffff. All the moldy cheese I was forced to eat growing up because mom wanted to save money.

We had our basement looked at when we started to build it in. We used a company called basement systems, the options were dig around the outside a refinish the walls properly, or do it on the inside. Basically they said water will get in travel down the walls then into a slotted trough that goes around the basement and is channeled to the sump. They also drilled through the walls at the window wells (below the ground surface) and put a pipe in that goes inside the house then in vertically troughed to the channel in the floor.

Framing in moved out an inched and plyed on both sides. We put in a suspended floor.

Our basement is guaranteed not to leak for the life of the house.

My parents' basement (in the hardest "sandrock") was arid dry for decades... built correctly. The 2011 'quake that damaged the Wash. Monument further breached the barrier... light moisture became an issue on mebbe 50' of walls in one corner.... basement became "musky". Cleaning (scraping) the bubbling walls (painted concrete blocks) and painting with Drylok a few times was futile. Did the complete "seal from the inside" walls with plastic type barrier, sealing a few cracks, and the trench lining the inside walls with holes drilled every few feet, sump, etc). Not one drop has entered that trench or the sump... ever. The basement is again bone dry with no issues .... a small dehumidifier does fine in the humid summer.

I'm happy .... the trench, sump, holes, etc. was $10K overkill in hindsight ... simply lining the concrete block walks with a barrier was sufficient. Been a few years now.... :)

My .02 worth of opinion and $15K worth of experience, and after ME painting that dang corner with Drylok at least 5-6 coats ... over several years :(.

Good luck!

Oh yeah .... mitigating the moisture breach from the exterior would have probably been 50K+ ... ea$y.

If nothing has been done to seal that wall, at a minimum it is wet on the outside with some moisture leaching through the concrete. It may be dry on the floor, you may not see water, but it is there. I would investigate further with a quality moisture meter and take some humidity readings over a few days, hopefully with some rain falling outside. I just noticed the Seattle in your signature. The rain part is easy. I owned maybe 10 personal and rental properties in the greater Seattle area over 30 years, several in Seattle proper and built in the early 1900's. It is really hard to have a true dry basement in an old house in Seattle. My 40s era house in West Seattle was the dryest and was a walkout in the back. If just storage, use something that doesn't hold moisture to keep things off of the floor and seal stored things appropriately. Should be fine. If you are wanting to build out the space into living space, more work may be needed.

Thanks for pointing that out - I'm in relatively dry Fresno, CA. I don't know how Seattle got in my signature.

The whiteish spots on the basement walls is very minor. There was no evidence of any water damage or cracks in the foundation and there wasn't any sump pump so I am assuming that the basement is mostly sound. I will rely on the home inspection and ask the inspector about this. There are two windows in this basement with dugouts on the outside of the windows and it's possible that water has gotten in thru there. A lot of cleanup will help this situation as well as grading the dirt around the house as most of the vents are right at ground level and I think the dirt should be a couple of inches below the vents, if not more.

My concern was mostly about how to clean this up so that I can paint or seal to make this basement look a little better and add some storage. It's a decent size room but not suitable for any kind of living quarters but would make a great storage area.

Of course, the property is not mine - yet. I made an offer, and they have until tomorrow to accept or counter.

In my experience (hundreds of home inspections) the typical home inspectors point out what they (and you) can see, then the rest of the report is a disclaimer to cover their butt.

There are better products for sealing block and preventing further efflorescence.

If you have time, tape a large square of plastic on the wall then seeing if moisture builds up on the back will tell you if the problem is continuing. Best to figure out where the water is coming from. I've found it's usually grading and settlement near the house.

After it is removed (chemically) we used to use redguard (yes, for showers) and then paint over to seal. I have seen a product although made for radon, it soaks in and seals the pores for moisture also. Think it was called "radonseal plus"

The box-store products like drylock don't seem to be effective in the long run.

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