Materials used: Melamine board ( leftover scrap in this demonstration) | (3) 2×4 boards – (2) to support slab mold – (1) for screeding concrete | Mailbox numbers of your address (hardware store) | Concrete (quikrete for this example) | Silicone |
Tools: Table saw | Kreg Pocket Jig | Impact Driver | Counter sink drill bit | Tap screws | Clamps | Concrete mixer ( not necessary ) | Concrete Vibrator (not necessary ) | Float |
This is what my old Trash can slab area looked like. Obviously, didnt like it and wanted more of a personal touch. I decided to inset the address numbers into the concrete. I removed the old slab and dug up close to a 2 inch rectangular area approx 2′ x 4′.
I had some left over Melamine boards from a previous project so decided to re-use some of that material. I set my depth to 1-1\2″ and cut the four sides (walls). I precut a 2′ x 4′ piece to place on the bottom of the mold ( top of the slab).
I used a counter sink drill bit around the perimeter. I did 4 holes for the 4′ side and 3 holes for the 2′ side.
I used a 1-1/2 ” board as a spacer to align the numbers. I mocked them up at the bottom of the mold. **NOTE** take in mind that you are molding backwards ( top is on the bottom ).
I relocated the spacer to the top and flipped the numbers so they will be right side up when the slab is removed from the mold. I used silicone on the edges ( not pictured well here because its white ) to prevent the concrete from leaking out the seams. Be sure to use 100% silicone. I grabbed a 30 minute quick set tube.
I used a mixer to speed things up but it is not required. you can definitely mix by hand. If youre using a premix bag, follow the instructions or just gauge as you go forward making water adjustments. If your doing it OLD SCHOOL, 2 parts sand/aggregate for ever portland cement add.
The first batch was a little runny. Im not too concerned as its just a trash can slab. But you are looking for a thicker consitency (almost peanut butter like )
I had some left over wire mesh from a previous counter project so I decided to use it instead of using small rebar reinforcement. (again, its an outdoor , low resistance slab ). I have a handheld concrete vibrator that I used to make sure the concrete got into every crevice and reduce air bubbles. Alternatively, you can use an electric sander and press against the side walls or use a mallot and just tap the sides to work the air bubbles out.
I used s scrap piece of 2 x 4 material to screed the excess and even it out. I have a video of another project, ill link here soon.
Here is a video sample of screeding the mold.
I used a float to smooth out the surface ( which is the bottom) so dont spend too much time on it. But if youre like me, you still want it as close to accurate as possible.
4 Days later, started removing the mold. I unscrewed the sides and started prying out the edges. **NOTE: Do not pry againt the concrete, it is still curing and in a brittle state, I used a putty knife to create a small enough gap that I can grab and pull back on it. Remember, there is silicone on the edges so it may have a bit of resistance, depending on how much you used. You’ll need another set of hands to help flip the slab once its out of the mold.
Details, Details. The letters that I used had screw holes in them and I completely forgot to silicone te holes in so some of the concrete bled in through the holes. Not a BIG deal, just a little more labor. My wife helped me scrape off some of the excess cement.
Once the numbers were exposed, this is the final product. Waiting a few more weeks until it completely cures and I will seal this bad boy.
Pretty nifty cheap little project if you like working with concrete. Get creative, add custom aggregates, dye or stain the concrete. Have fun! If you have questions, feel free to post a comment.