Custom concrete pavers III

Maybe you're wondering how the concrete pavers that I wrote about earlier turned out. Here's what the bottom (now the top) looks like.



I didn't wait long enough for the caulking to dry and consequently it stuck at the edges of the leaves. Experience has shown that it's not too hard to remove.

I think I'll add some red to the color mix.

Custom concrete pavers II

Here's something I did back on the 23rd.

In Forms for custom concrete pavers I showed how I make the forms for the pavers that I use in my yard. Here's a bit more detail on the moments before a pour.

I assembled the paver form the night before, and it took about 16 H for the silicone caulking to dry to a state where I thought it was OK to pour. I wasn't 100% right on that - it could have gone longer. I used white, because that's what I had on hand, but my preference is for black since it's easier to see against the white of the form. My goal was to make a water tight tub for the concrete to set up in and then add a few artistic touches that make this a truly custom job.

I've added plenty of leaves before, mostly from the Magnolia in my back yard. Normally I'll press a leaf down into carpenter's wood glue with a board and a brick. This time I used Western Redbud leaves which are more flexible than the Magnolia and also, because it's a native tree, more meaningful to me. I set them in a bed of the same silicone adhesive that I used on all corners, but didn't press them down other than with my fingers to bed them in. I don't know if this feature will turn out. We'll see.

I also added a hole in the paver to let me grow a small plant or maybe just to break it up visually. I could always just put polished rocks in it. The form for the hole was cut down from a large PVC coupling using a hacksaw, then slit up the side. The side slit is intended to let it compress and come out easily, but I filled the slit with caulking because I was out of packing tape. What I really needed was a wider side slit with tape over it. I anchored it into the pouring table with a piece of wood and two screws and gave it the same waterproofing treatment that the rest of the from received.

Here's the completed form with some tools of the trade. On the right side of the form, I've aligned the edge with the edge of the fluorescent light cover which will give me the surface texture. At left, the little triangular braces hang out over it a bit. The braces are Maple, a hardwood.

The Christmas box in the picture holds my drill bits. The bottom of the mold is fragile - I suggest drilling first before trying to insert screws.

The top of the form edges received a layer of clear packing tape, until I ran out. This prevents water intrusion which can really degrade the form. Cheng seems a bit anal about this, but that's why he makes beautiful pieces. My previous experience says that it's not critical, particularly for garden pavers. Still, the form will keep its life a bit longer if I use it.

I level out the form in both axes using some left over shims and spacers placed under the table.

I add color (this time I was a bit bolder than previous attempts and added about half of the colorant). I also add about a fist full of polypropylene fibers (at left below) to strengthen the concrete.


Below, the concrete, mixed and ready to shovel into the form. Those Atlas gloves are invaluable. I also use a NEMA-approved dust mask when pouring the concrete out of the sacks - the dust is mighty fine and quite alkaline. I use a special hoe with some holes in it made for mixing concrete, but I'm sure a plain old hoe would be fine.

The volume of concrete shown comes from two 60 pound sacks of Quickcrete 5000 and it fills the form nearly to the top. If I were pouring a countertop I might be a bit more anal about getting right up to the top of the form.

I have always found that the concrete takes nearly twice as much water as the bags say you need. I used about 1.8 gallons for this batch, and the bags say that 0.5 per bag is sufficient. They also say not to exceed twice the recommended amount, so I'm OK. Add some of that water to the empty mix container before you add the dry concrete so that the bottom gets wet. Mixing ~130 pounds of concrete with that hoe is a work out!

Forms for custom concrete pavers

Because it was so windy Sunday, I stopped my exterior painting and prep and used my table saw to make parts of the paver forms that I'll soon need. I cast my own concrete pavers and I'll need more outside my new bedroom door - at least 4 and likely 6+. I've grown to really like the advantages of using stacked or ground-set pavers and bricks for garden hardscape - the ability to move and reset the pieces is a huge advantage over poured-in-place or mortared-in-place pieces is huge.

However, it's also fair amount of work to cast pavers using the methods that I'll tell you about. For one, the paver size I call for here is probably 120+ pounds when its done so you need to think about whether you can even heft that around your yard and the sweat you'll build up mixing that volume of concrete. Nonetheless, the payoff is something that's completely custom and potentially wildly different than your typical poured-in-place or purchased paver.

The sides of my paver forms are 2.5" x ~19" x ~32". I cut them from melamine-coated particle board. The 2' x 4' melamine sheet that I purchased from Home Depot gave me the pieces that you see here - enough to make three forms and have three long pieces left over for spares. An efficient use of material is to cut the six short pieces from the 2' side of the melamine board first, then the 9 longer ones from the long side of the remaining board. You'll eventually cut the boards to their final length, but the cut off portion is minimized using this method.



The exact size of the pavers I've already made was 19-3/4" x 32" which is very close to the Golden Ratio. The 32" dimension was set by the largest width I could accomodate in my side yard. I'll keep those dimensions with the new forms in order to emphasize continuity and repitition across the yard.

From past experience, I know that it's difficult enough to make two pavers at the same time, both from an available space standpoint and from a labor standpoint. All that concrete mixing and hauling is hard work! I have materials enough for three, so that third one will be an option if I can make it work.

When the forms are assembled, I place them on a textured piece of plastic like this. The plastic is on my "pouring table", a 5/8" piece of plywood with 1x4 stringers underneath to keep it flat under heavy load.

The textured plastic is from a fluorescent light and available at Home Depot for 5 or 6 bucks. I used a pebbled pattern, but grid patterns are also available. These form bottoms are actually pretty expensive since it's only reusable a couple times before it degrades too much.

The forms are then sealed along all the corners. I use a black silicone-modified latex (gotta check this) . Black has a nice contrast against the white melamine, so it's easy to see. Cheaper non-silicone caulking forms a much tighter bond to the paver and creates a problem when I disassemble the mold. Smooth the seal down with a wet fingertip and you have a nice chamfer on the edge of your paver.

Decorate the bottom of the form with things that you like. I've had good success with Magnolia leaves and garage ephemera. I weight the leaves down with bricks and glue them to the form bottom with carpenter's wood glue. They eventually come out of the concrete, leaving a pleasant impression behind. I've also used pieces from my old Alfa Romeo, bicycle parts, and coins. Flat, thin, pieces like coins that are to be embedded in the concrete are harder to work with- they can pop loose. One way to address this is to epoxy a wood screw on to the back of the object to give it some grip into the concrete.

Then it's all about mixing and pouring the concrete. More on that later....


The basis for my concrete knowledge comes from having done this before. But prior to that, I read Fu-Tung Cheng's marvelous book, Concrete Countertops. Eventually I will have a concrete countertop as well, but that's a story for another day.

If this information is useful, try the concrete paver tag link at the bottom.