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.