Stain your concrete with Fertilizer?
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Have you ever read the label on your lawn fertilizer with the stern warning against getting it on concrete? Have you ever wondered why such a warning is issued or what would happen if you fertilize your concrete? Keeping in the DIY spirit with Hales Homestead, I’m going to reveal the mystery about what happens when you intentionally fertilize your concrete in a controlled way resulting in flooring character you’ll want in your home and garage spaces.
As I perused the interwebs during the 2020 COVID pandemic, I happened upon videos on simple living solutions by a youtuber, Kirsten Dirksen. She produced a video of Tuscon based, Brad Lancaster, which had a very brief segment (see 14:20) where he used Ferrous Sulfate to stain his concrete floor producing a nice brown natural tone to his kitchen floor. What caught my attention is that he was able to easily stain his floor for about $2 using water and lawn fertilizer. Ferrous Sulfate AKA Iron Sulfate or simply Iron is a component in many fertilizers available at your local hardware store for $5-$10 a bag.
About 5 months after hearing of such a concept, Caryl and I were trying to think through the type of finish we wanted on our 11’ x 18’ concrete floor in our new studio project. We leaned toward some form of staining the floor due to all its imperfections, cracks, and uneven pitch. The backyard studio project was already taking on a natural shabby look with barnwood on the ceiling and exposed 4”x 6” beams running through the middle of the ceiling. After some digging around Youtube for a while, I was finally able to recall the exact video and 10 second clip. We then decided that staining our floor with iron was worth a try!
Preparation
Our floor had a significant crack running the entire 18’ length of the room. Another crack lined the outer edge of the floor. Paint and oil stained the entire floor and it was also covered with drywall dust. We had a huge task ahead of us to get the floor ready to receive some stain. My first step was to use a grinder and masonry wheel to soften the edges of the cracks to prepare them to be patched. I had to deepen grooves in some spots to ensure the patch would take hold. For filling cracks, we decided to go with the DAP Gray Patch and Resurfacer which may be picked up at your local hardware store. I attempted to apply the mixed up patch like I was icing a cupcake using a plastic bag and cutting one of the corners. This failed! I’d say I probably had the wrong consistency so I ended up using a small concrete tool to stuff it into the crack and smooth it. I used a 4.5” grinder flap disk to grind the patch once it was dried to smooth it out and to remove the paint and other blemishes from the concrete.
Cleaning
Once the patch was set and hardened, I used a TSP mixture in water to get the hard to remove oil spots and left over paint stains. I’m still scratching my head on where the paint stains came from. There was no evidence of any paint on the walls in that building. The drywall dust seemed to be the most difficult to completely mop out. It seemed like I went through 5-10 buckets of mop water just to get it clean enough to get to the point of applying the fertilizer.
Application
Once the floor is free of stains and dust, it’s now time to mop on the fertilizer and water mixture. We used a 5 gallon bucket, a 4 lb bag of Hi Yield Iron Sulfate, and some water for the application. Mix in 1lb of Iron sulfate with 1 gallon of water into the bucket mixing well to ensure the pellets are all dissolved. Mop the solution generously onto the floor getting coverage over the whole surface. Be careful to avoid splashing it on onto dry wall and trim boards as they will be stained. As the warning label warns, will stain concrete and surfaces! If the walls and trim are painted, it may be worth your time to put up plastic or something to keep the solution off the walls. We were fine getting the stain on the baseboard as it was already dark. We went with 2 rounds of stain to get an even richer earth tone on the concrete. Some people go with an even darker stain by brewing a strong batch of coffee and mixing it into the iron and water mixture. Once you’ve made your first application, take a break and let it soak into the concrete. You’re gonna think I’m full of it after you mop on your first application. Come back after an hour or so and you’ll notice the stain beginning to take effect. This will be the point to decide whether to apply more stain or not. After a couple applications, you’ll notice dusty streaks on the floor. I took a wet sponge and softened the lines of the streaks so the coloring looked more uniform.
Sealing
Once you have your desired color and darkness, it’s now time to seal the floor to lock in the stain. We used a gallon of Drylok Natural Look Sealer for the purpose of sealing the floor protecting the stain we’d just applied. After 2 coats, we got the desired sheen and uniformity we were looking for. The smooth surface also allows for easy cleaning wiping up spills of most kinds.
This project turned out better than we’d hoped for. I hemmed and hawed about practicing on a section of concrete in my garage but then just decided to let it rip and I’m glad I did. Having seen the ease of application and how cost effective and safe it is, the garage is looking like the next prime candidate for an iron stained floor makeover.