Clean a Concrete Basement (Before Painting)

The basement walls and floors were pretty dirty when we started.

I spent some time searching online and listening to what others suggested:

• What is the best homemade wall cleaning solution?
• How do you clean cement properly?

If you’ve read some of my other posts, you’ll know we had to evict packrats that had taken over. So this wasn’t just a quick clean—I wanted everything properly cleaned and disinfected before even thinking about paint.

Even though I didn’t see visible mold, I kept thinking:

“What if there is mold in the concrete?”

So I made sure everything I used would fully clean and disinfect the space.

These walls were pretty dirty as you can see by the pictures, and if you have read any of my other post you will know that we have had to evict the packrats that wanted to take over.

Cleaning Concrete Walls before Painting

The first thing I did was use TSP (trisodium phosphate) dissolved in warm water and scrubbed the walls with a stiff scrub brush.  A TSP cleaner for pre-paint wall prep works really well for cutting through grease, dirt, and old residue.

I let the walls dry and then scrubbed them again with the same solution.

After that, I rinsed everything down with plain water using a sponge.

At this point, the walls still looked dirty—and honestly, I just couldn’t bring myself to paint over them yet.

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Deep Cleaning and Mold Prevention

Next, I started looking into deeper cleaning methods, especially anything that would help prevent mold.

The method I chose used laundry detergent and bleach—not mixed together, but used in separate steps.

What is required for this procedure is:

• Tide laundry detergent
• Clorox Bleach
• A hard bristle brush with  a handle
• Water
• Two buckets
• Sponge or rags
• Gloves
• Mask
• Old work clothes

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Step 1: Laundry Detergent Wash

We mixed about 1/4 cup of laundry detergent into a bucket of water.

Scott scrubbed the walls with the solution while I followed behind with a sponge, rinsing and wiping everything down.

Then we rinsed the walls again with clean water.

The walls were starting to look better at this point, but I still wanted to try one last thing.

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Step 2: Bleach Treatment

I mixed a bleach solution (about 2 ounces of bleach in a 16-ounce spray bottle) and sprayed it onto the walls.

We let it sit for about 30 minutes before washing it off with clean water.

At this point, the walls were finally starting to look better—but I still wasn’t done.

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Step 3: Final Disinfecting Clean

This might sound a bit surprising, but I used Pine-Sol as a final step.

Pine-Sol is known for killing 99.9% of bacteria, so I sprayed it directly onto the walls and left it overnight.

The next morning, I washed everything down using a sponge mop and clean water, then dried the walls with a rag.

 

Now I finally felt comfortable moving on to paint.

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Cleaning a concrete floor

Cleaning the concrete floor was a little easier than doing the walls.   The first thing we did was clean it with Muriatic Acid.
Ro-Tyme Muriatic Acid, 4-L

Using Muriatic Acid Safely

This step helps:

• Remove old flaking paint
• Clean deep into the concrete
• Etch the surface so new paint adheres better

We applied a mixture of 1 part muriatic acid to 3 parts water using a mop.

⚠️ Important:  Always wear gloves and a mask and work in a well-ventilated area

Be sure to read all instructions carefully before using.

We used a slightly more diluted mix just to be safe.

After applying it, we left the floor to dry overnight.

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Final Floor Cleaning

The next morning:

• I rinsed the floor thoroughly
• Washed it again with water and Pine-Sol
• Repeated this process two more times
• Finished with a final rinse using clean water

Once everything dried completely, I painted the floor with an oil-based concrete paint.

✔️ Final Thoughts

All in all, I may have gone a bit overboard with the cleaning—but I wanted it done right.

Now the basement feels cleaner, smells better, and I know it’s ready for paint that will actually last.

If you’re working on an older cabin or off-grid space, taking the extra time to properly clean concrete before painting is absolutely worth it.

👉 If you’re fixing up a cabin like we are, you might also like my guide on off-grid cabin projects and upgrades that make daily life easier.

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Disclaimer:
Always use caution when working with cleaning chemicals. Follow product instructions, wear protective gear, and ensure proper ventilation.

updated March 2026

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