Monday, December 13, 2010

Lay It Down

I mentioned in a previous post that I had finally poured the countertop in the pantry this past week. It went fairly well but with one minor problem I will get into later. I had the cabinet made with the face plate 3/4" higher than the walls of the cabinet so that I could lay in a 3/4" piece of plywood and have everything the same height. Then, I simply clamped the front edge form to the cabinet, with a 1" spacer between it and the cabinet. This gives me the standard 1" overhang of countertop. I then caulked every single crack within the area that would receive concrete with silicone caulk. This would keep the wet concrete from weeping water down into my cabinet. I also ran a good thick bead in the front bottom crack of the form (what would be the front bottom edge of the concrete counter.). Silicone gives the concrete a nice smooth finish and will release it easily.

I also transferred my finish elevation to the back wall and installed a wood strip (which you can see here) at that height to serve as a screeding line. It stays in and will be covered by the backsplash. Then I simply mixed the concrete and shoveled it onto the counter form, making sure to pull the wire up to about the middle of the concrete. The countertop is about 2 inches thick.

Now, if you look closely in that last photo, you can see my mix was just a little wet, so when I poured out that water started to rise to the surface, as it should. Now, you don't want to keep working that water back into the surface of the concrete, as it will weaken it, so I opted to place pieces of clothe on the surface to expedite it's removal. Normally, a little water is always going to come up and you just float the concrete down once and leave it alone. It will evaporate on it's on. This had a good bit of water coming up, so soaking it up did help but it caused me to have to float (or smooth) the concrete down several times, which in turn, worked some of that water back into the surface. So, today I noticed a few places in the counter where the cement is getting powdery and flaking off, exposing the sand and lower surface of the counter. I believe there are several things I can do to remedy this but it's a pain.

This is the counter right after I floated it off and got it on grade. I had to mix the whole thing in two batches so the right hand half of the counter is very hard, because I got the water right.
As I said, once the concrete is floated down just leave it and check on it every once in a while. You can tell when the water starts to evaporate and the surface will start to look slightly dry. After this point you can run afloat over it a couple of times and then you switch to a trowel.

What I have in my hand here is a trowel; a float has a much thicker blade. They are NOT interchangeable if you want a truly slick finish. With the trowel you are in effect, burnishing a slick finish on the concrete. A fair amount of pressure must be applied as you do your sweeps. And, if you look closely, you can see one edge of the trowel is held up, so that only the back, or trailing edge touches the concrete. You use this technique with the float also. If you let either lay flat as you make your pass it will 'grab' the concrete and simply gouge trenches in the surface. As the concrete hardens you can see the trowel begin to burnish it and the pinholes close up. However, don't work it too much at one time. Make one pass and stop. Come back 30 minutes later and do another. I started pouring this counter at about 10:00 a.m and probably made my last pass about 9:00 p.m. so it is not a quick process unless you are in a very hot environment. But then, I did get mine a little wet.
Other than the few small spots I mentioned it came out real nice I think. I will show ya'll finish pictures soon and I even installed the hardware on the cabinet. Now, I just need to pour the backsplash and install that.


ezrablu said...

I LOVE IT! I've been planning on putting a cement counter in my little cabin when I build it. Great photos and thanks for the details and explainations. AWESOME POST!

Ed said...

This post and your last posts on this subject have left me wanting to do something similar when I build my house. The only difference being that since I am wanting to build a thin shelled concrete monolithic dome where the interior wall is concrete, I am planning on cantilevering my counter tops to the wall in places where no cabinetry underneath will exist.

edifice rex said...

Hey Ezra! thanks! if you have never poured concrete before you might want to pour a little step stone or two first just to see how concrete reacts before you do your counter. It takes some practice to get the hand of finishing.

Hey Ed! Yeah, that would be great; you know, I suspended the vanity top in the bath and it's not so hard to do. I'm sure you would have a great design.

Floridacracker said...

Neat! Looking forward to seeing the final product.
I really appreciate the tips on finishing. I always mess with my concrete products too much and never get the finish I was after.

I have this outdoor kitchen plan floating around in my head and I think concrete countertops in the prep area would be just the thing.

Beatrice P. Boyd said...

Hi ANnie, looking forward to seeing the finished counter in a future post - very descriptive post here to explain the process. Did Capt Jack take the step-by-step photos for ya?

edifice rex said...

Hey FC! thanks; yeah, most people have a tendency to want to work the concrete too much but this just delays it's setting.
Yeah, concrete countertops for outdoors would probably be wonderful.

Hey Beatrice! yeah, Jack took the photos; he's good about that.
Hopefully I'll have the thing finished soon.