Saturday, December 27, 2008

Carved In Stone Part 1

I'm so happy that I finally just bit the bullet and poured my concrete countertop in the bathroom. It was no big deal but I just kept putting it off. Well, I did (and still do) have more pressing exterior issues to deal with but it is nice to have this done. I was actually able to beg a day off from work last week and knock it out. Sunday, Allen set the sink and hooked everything up for me so it was functional for Christmas, which was nice.
Excuse the poor quality of the photos. I almost forgot to even take any and then I was in a hurry so they didn't come out too well.
First, I determined that I wanted the top of countertop to be at 32". Standard height is 30" but that seems low to me. The countertop itself is 2" thick and I used 3/4" material to form the bottom, so I dropped down 2 3/4" to the top of the 2x4's that I attached to the walls to support the "floor" of the form. I ran 3 1/2" screws through the 2x4's into the studs so that makes for strong support and can be easily wrecked. Well, should be. As I mentioned before though, I was in a hurry and not paying attention so I ran a few screws in that could not be gotten to after the concrete was poured and so some of the form just had to be busted to be removed. Even us "pros" make mistakes if we are not thinking.

I found some kind of plastic trim (I think it was for screen doors or something) that made a perfect flexible edge. It bent lengthwise but not widthwise. After I had my 2x4's attached to the wall I scabbed two 1x12's together to make the floor and temporarily attached it in the corner so I could draw out the shape I wanted. I made this base a little oversize and square so I would have plenty of room to draw. I also made a template for my sink shape and placed that on there to help determine the shape of the countertop. I just free handed the shape I wanted for the outer edge with a pencil and then took the base down and cut it with a jigsaw. I glued together 4 small sheets of Dowboard and cut the sink template out of that. the red line you see on the back wall is my grade line. I doweled four #4 bars into the studs in the wall which protrude about 12 " into the slab. I tied a grid within the form out of #3 bars. I had to use slightly thin rebar to get it all within the 2" of mud and the #3 bars are easily bent too. I used lots of construction adhesive on the dowels where they went into the studs. I put 2 dowels in each wall and so that makes a nice perpendicular grid to support the slab once the forms are dropped out.

Here you can see the shoring underneath: the 2x4's on the wall and I cut three 2x's to shore up the outer edge of the form. Even this tiny bit of concrete will be heavy. The countertop has a slight drop to the outer edge. I think about an 1/8" from back to front. I just didn't want any water to run towards the wall and you will never see that slight of a fall. I used 100% silicone to caulk all the cracks where any concrete would be. This prevents a mess from running down the walls when the mud begins to weep and gives you a nice slick finish on the front, bottom edge. The top, front edge I'll have to grind smooth.

Now, I used a mix of one bag of Sackrete to a 1/2 bag of non-shrink grout. Non-shrink grout is mostly portland cement and will help strengthen the mix and I think it helped give it a nicer finish. This is what mud looks like right after it is floated off. I tapped the underside of the form with a hammer to "vibrate" the mud and remove as many air bubbles as possible. You always need to vibrate your concrete in some way. This helps in surround the rebar fully and become as dense as possible. Vibrating also helped the concrete flow down to grade pretty much on its own. Of course, this is such a small amount of concrete it's almost on grade as soon as you get it in the form!

When it is vibrated correctly, this is what it looks like. It gets really wet looking on top and you start seeing these little volcano-looking air pockets pop up. Now, you can vibrate too much but unless you are using the big, mechanical vibrators like we use at work, that is not going to be a problem. I then floated it off one more time to make sure it was on grade and get a little smoother finish. You then just have to let the mud sit and start curing. The more you mess with it, the longer it will take to start setting up because you need to let that water rise up to the surface and start evaporating. And remember, concrete cures, it does not dry. I will show the rest of the process in the next post and the finished product. I think it came out well. If anybody has any questions so far please ask. I know I don't always explain things well.


Anonymous said...

Can't wait to see the finished product ER!

Elizabeth said...

Excellent post. I want to make concrete counters in my house so this was very interesting. Glad you got some time off. Annie, have you heard from Ron?? His blog is no longer available.

Anonymous said...

I am pretty much decided on concrete counters for our next kitchen. Thanks for posting your process, it is always nice to see someone who knows what they are doing give it a shot first!
I second your decision on the taller than average counter height too. We went with 42" counters in our kitchen and it was the best decision we ever made. I am 6'2" so that explains my pleasure working at the taller height, but even Gary likes them more now.

Maya said...

Hmm, not sure why my comment above came up as anonymous?

Floridacracker said...

Excellent Annie! I feel inspired now to give this a try in an outdoor kitchen area I've been thinking about.

Keep the pics and info coming!

edifice rex said...

Hey Molly! Well, hopefully I'll have that soon!

Hey Elizabeth! thanks! I plan to do concrete in the kitchen and pantry also and I'll show that because they will be done a little differently. I have not heard from Ron; apparently he has kinda dropped out of sight. Don't know what is going on.

Hey Maya! Maybe we are all getting taller because a lot of people seem to be going to taller countertops! At 6'2" can see why you would really like them. I think I wil stick with the 36" kitchen height but I'm only 5'6"!

Hey FC! thanks! I will try to provide plenty of info on this and the pantry countertops which will be poured over cabinets. You can handle such a project fine. The hardest part is getting a hard, slick finish on the concrete. If I don't explain something fully just tell me.

Rich said...

I stained a concrete floor a number of years ago and the store where I bought my supplies had a stained concrete counter top display that really interested me. Some of the counters I saw in the display looked almost like polished natural stone or polished wood. I've been itching to try my hand at pouring some of my own counters and your post has revived my interest.

I do have some questions, why did you use the no-shrink grout mix instead of just portland cement?

Is your counter going to be self supporting, or are you planning on building something like an under counter support bracket?

Are you planning to stain your counters?

When I was initially interested in pouring some concrete counters, it seems like there were things available like edge molds (for a rock or a sculptured edge effect), and a product that was supposed to "slick" up the surfaces of the counters.

If I remember it right, after the forms were removed, the concrete would be stained a base color, the portland cement based "slickening" agent would be applied, and then the whole counter would be stained again (once or twice) followed with a sealer. It seems like small imperfections in the first pour actually enhanced the appearance of the final counter because the "slicking" process acted like a grout to create veining that would be present in natural stone.

It seems like the possibilities would be endless with concrete counters; I could stain and re-stain them, sandblast or grind patterns or designs with or without grouting or staining, inlay copper or brass designs into the initial pour then sand it flush, etc.

Thanks for reviving my interest and starting the creative process.

karl said...

i am anxious to see your next post...

i want to use concrete for all the counters and sink in our summer kitchen. that project is on a far off queue.

i guess your sink contains the faucet? i would have expected to see little blue foam holes in the concrete for them?

exciting, i like to see things that i have never done before and plan to try one day.

congratulations annie.


edifice rex said...

Hello Rich! Nice to hear from you.

I used non-shrink grout just because I happen to have a bag! That's what determines about half of what I do.

This countertop is going to be self-supporting. Because the slab is in a corner and able to be doweled on 2 sides I feel this is OK. The slab is only 40" long also. If it were much bigger I would probably put brackets under it.

I do not plan to stain them but might put a coloring agent (black iron oxide) in the mix when I do the kitchen countertops because I want them a little darker. I like the natural color of concrete.

Yes, there are lots of things you can make yourself to give the edge a different shape. and yes, you are right, the options with concrete are almost endless. You can add materials, colors, shapes, all kinds of things. You can etch patterns in it, inlay glass, copper, whatever. It works a lot like clay, which I guess, is one reason I like it so.

As far as 'slicking' up the surface, I'm not so sure about that. I'm sure they make something and I do know there are topping mixes you can make but I just try to get the finish I want on it when I finish the concrete. Now, I know this takes a lot of practice and most DIYers have not finished concrete enough to even know how to get a real slick surface. There are also a variety of diamond sanding discs, blades etc. for use on mini-grinders that work extremely well.

Thanks so much for your questions and comments. Hopefully the rest of the post will help you some.

Hey karl! thanks! Yes, you are correct, the sink does contain the faucet or elso you would have to block out for the pipes. Hopefully the rest of this post will help you also with your project.