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Yes, I am bringing this topic up again. Sorry to feel like it keeps getting rehashed, but I need the full skinny on the subject. Every archive keeps me hanging like a This Old House article. One post mentioned using a mold to form the countertops upside down. What do you use for the forms so the surface is smooth? As far as sanding concrete, I am a little crazy but not sadistic, so this is out of the question. Forming the tops in place creates a need to trowel like a man possessed, yes or no? Does this create a smooth surface that is acceptable? I still have yet to find a formula for the concrete mix. Is a ready mix product such as fiber reinforced or a sand mix, possibly with an acrylic fortifier going to give acceptable results in a mold or formed in place? I am a contractor myself, and am familiar with concrete but only in footings and foundations. Help me out please, I want to do this in my house.
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The cheapest thing I've used for mold material is the polished surface plastic laminate. I bought some from the supplier that was discontinued and really ugly, it was cheap. You CAN sand the surface to make it extra smooth. Use a random orbit sander with wet/dry paper. Use it wet, of course. This means using an air-sander, and you'll probably have to cut your own sandpaper sheets and use the goop that sticks them on. Troweling is possible, smoothness depends on your ability and how many square feet you need to do at one time. My suggestion: make samples in your shop, see if you are satisfied. You'll find out how hard it is to trowel and how many air bubbles are in the surface (formally the bottom) of cast tops. Use a 6 sack mix, pea gravel. Again, experiment, don't take my word that it will work. I don't think fiber reinforced will be very nice, but I don't want hairy counter-tops. I also think that if you use an acrylic fortifier you will have a difficult time sanding and I'm sure it will color the mix. Think ahead in any case and decide how you will fill the air bubbles that will occur.
*Why would anyone who has experience with concrete want it in the kitchen too or want to eat off it.Have you figured out HOW you're going to seal it and with what. Most sealers are toxic.Experiments are best left to the labs.
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Gabe
Let me guess your about 90 years old.
You still use a ringer washing machine.. wait a minute.. your wife still uses a ringer washing machine and a plastisizer is some one who drinks too much.
Every thing I see posted by you is negitive. Lighten up and enjoy what can be created by natural and enviormental friendly products.
checkout this web site for what can be done concrete
http://www.decrorative-concrete.net
To Tim
AEC info web site under concrete forum has quite a bit on concrete countertops
Rather than sand paper grind it, you can get it as smoothe as you want.
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Dearest Rob;
I hope your estimates are better at the jobsite.
You missed by 40 years, my wife uses state of the art, I love my profession and enjoy helping others in my free time.
Have you ever seen those harvest gold or olive green discarded washing machines by the roadside, waiting to be picked up, that's what I'm trying to prevent.
Things sometimes look good at the time, but 5 years done the road it could look pretty sad. AND IT COST A LOT OF MONEY TO REPLACE THEM. If the concrete countertop fails, will you volunteer to pay for a new one.
Don't be like those ducks that we're always having to rescue from the oil ponds. They fly by, take one look and decide that the shiny surface is water and dive right in.
Someone should at least post a warning sign.
*Tim, this is not a slam and is not mean to be mean, but pouring footers and slabs is not a background for pouring and finishing a concrete counter top. Concrete is unforgiving. you have to start planning before you think about starting. Personally I think that pouring in place is the way to go. This allows for a no seam look that will surpass the"soild surface" stuff out there. In order to get this look you will have to trowel and grind and sand. As far as sealers you can use the FDA approved finishes that woodturners are using or contact any of the major concrete chemical companies for info. This is not a quick or easy job. The best thing to do is practice first. This allows you to chose colors and your finishBest of luck on your top
*I recently saw a TOH rerun of the Arizona project that included a poured-in-place concrete countertop. For a 2.5" slab, they used styrofoam forms for the edges, which were removed when the concrete had cured sufficiently to hold its own. All exposed surfaces were screeded, floated, tamped, troweled, and finish troweled, and troweled some more. The job seemed to take about 16 hours of intermittent work. The result appeared worth the effort.
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Tim, here is a link to a Mongo post detailing how he did his own counters. I've saved it for the time I have less than 6 projects going so I can make a sample. Hope to get to it this summer to see what I can do with it. http://www.taunton.com/breaktimearch/messages/8158.htm Waiting for longer days, Joe H
*Definetly pour in place. One detail that looks really hot is using crown moulding for forms. Make some samples to test stains and finishes on. Abuse these samples to test durability also. Good luck.
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My only word here would be if you want something that looks like solid surface use solid surface. don't try to make one product look and feel like another. It will always be an imitation. If you and the people who will be using the counters like the look and feel of concrete, go for it. Like anything in building there are lots of different ways of doing it and lots of ways to screw it up. So research, practice then do it or hire the work of someone whose work you like.
*Tim, here are a couple pic showing the inverted mold method.The first is of the form. Gloss laminate bed and edges, rims are 2x2 stock. Clamps are holding edge-molding in place during fabrication. This is during the pour. The finished slab is 2" thick, this shows about 3/4" concrete down with hardware cloth and rebar in place. This was for an island, you can see the cooktop cutout, sink blocking, and dowels set behind the sink for the faucet and soap dispenser. Size was about 46" deep by 78" long.Here is one of the finished items, a small desktop. About 36" wide and 20" deep, let into a wall pantry. It was placed right after unmolding, the final color is slightly lighter. You can see the reflection of the beadboard on the desktop. I've been able to get very nice surfaces using formica in the mold.
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Hey Mongo!
Please don't leave us hanging! Nice pix you provided, great work...what type of a mold release did you use if any, what cement ratio do you recommend, what colorant and what sealant are you using?
Have you considered dropping in some (flat) limestone chunks or similar here and there on the primary surface to break up the absolute uniformity (sterile/contemporary) of the final finished top a bit? The possibilities seem to be endless.
I'm ready to do a "test" as soon as you point me in the right direction.
Thanks in advance!
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Espanto,
I didn't use any mold release. The formica is so glossy there really isn't much for the cured concrete to hang on to. I did put gloss urethane on the molding to get the smoothest possible finish on that, though.
I discussed the mix, colorant and sealer on the archived post. Write again if you need more specific info then what is contained there.
I don't much go for the "embedded objects" idea. I'm sure some interesting effects are possible, but I wasn't interested. The pea gravel gives a nice mottled coloring to the surface, many variations of gray/charcoal/black. Color options are fairly wide open if you consider using white portland cement with various pigments.
Did you check out the archived post that Joe referenced in his response? Here's the link.
Good luck
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Thanks a ton Mongo!
There's a lot of rich people put here in the L.A. area that want truly unique "custom stuff" that their neighbors and friends don't have...and they're willing to pay for it! I understand that they'll even request you sign a "confidentiality agreement" to not divulge details about what they have nor how you did their counter tops, etc! Amazing eh?
*Mongo, >As a ready-mix producer I am very interested in any project for my home that uses such a wonderful and versitile product. Did you look into using a light weight aggregate such as expanded shale. I would research some of the new fiber products on the market, some early fiber got a bad rap "hairy concrete". Has anyone tried any acid stains to acheive different color effects? > Thanks Dave
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Due to the smalll size of the samples I've done in this area, I used perlite (Bagged from the garden center)in some samples. Worked out great in terms of reducing weight...dropped it by about 40% if I recall. I've got a slew of samples that have been outside now for a few years. Perlite has held up as well as the rest. I thought I might have run into problems from freeze/thaw, but none to date.
The only problem area I had with perlite was that there were a few voids in the perlite samples. More entrained air, I suppose. Nothing drastic, as they can be filled with either a slurry or epoxy.
I've avoided the acid stains so far. I haven't had the practical need to go down that path, so I'm not
up to speed on the possibilities. Sounds interesting, though.
If you have any info, I'd certainly be interested.
Thanks, and welcome to the discussion...
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Mongo, '>' You might look at the "L.M. Scofield" brand of concrete colors. They produce intergal, shake, and acid stains as well as sealers and release agents. I've used the acid stain on a couple of floors (both residential and com.) with good results. From what I've sen they make about the best products out there. One note - If you do use any light weight aggregate, be sure to soak it in water for at least 24 hours prior to use!! This comes from experience. Thanks, Dave
*TimWe just finished a concrete countertop and are happy with the results. We poured in place, using walnut nosings as forms. Using the extra concrete we made practice blocks (1'x1') to try out stains and finish. Our finish did not come out as smooth as wanted, so some sanding was required. Touched up some areas with a diamond file which worked very well (diamond sand paper would be great). also found out that epoxy mixed with fine sand worked well for patching a crack. We colored with an acid stain. Tried a lot of different methods to apply the acid; brushing, dribbling, scrubing, tried mixing colors together,layering, the list goes on... Got lots of neat effects; we were trying to get "something" like our rock chimney. The only problem was that it was very hard to come up with the same color twice. The acid reacts slightly differently with the concrete each time. We settled on a range of color that we liked. To get the mottled effect of our stone, we used 2 colors, brown and green, and applied it with a spray bottle. The spray bottle assured a random pattern, also applying one color lightly over the other.As for finish, Conrad Solvig sells a "USDA approved for food contact" acrylic sealer that looks great. Hard to brush on though, works better sprayed.
*TimWe just finished a concrete countertop and are happy with the results. We poured in place, using walnut nosings as forms. Using the extra concrete we made practice blocks (1'x1') to try out stains and finish. Our finish did not come out as smooth as wanted, so some sanding was required. Touched up some areas with a diamond file which worked very well (diamond sand paper would be great). also found out that epoxy mixed with fine sand worked well for patching a crack. We colored with an acid stain. Tried a lot of different methods to apply the acid; brushing, dribbling, scrubing, tried mixing colors together,layering, the list goes on... Got lots of neat effects; we were trying to get "something" like our rock chimney. The only problem was that it was very hard to come up with the same color twice. The acid reacts slightly differently with the concrete each time. We settled on a range of color that we liked. To get the mottled effect of our stone, we used 2 colors, brown and green, and applied it with a spray bottle. The spray bottle assured a random pattern, also applying one color lightly over the other.As for finish, Conrad Solvig sells a "USDA approved for food contact" acrylic sealer that looks great. Hard to brush on though, works better sprayed.
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Yes, I am bringing this topic up again. Sorry to feel like it keeps getting rehashed, but I need the full skinny on the subject. Every archive keeps me hanging like a This Old House article. One post mentioned using a mold to form the countertops upside down. What do you use for the forms so the surface is smooth? As far as sanding concrete, I am a little crazy but not sadistic, so this is out of the question. Forming the tops in place creates a need to trowel like a man possessed, yes or no? Does this create a smooth surface that is acceptable? I still have yet to find a formula for the concrete mix. Is a ready mix product such as fiber reinforced or a sand mix, possibly with an acrylic fortifier going to give acceptable results in a mold or formed in place? I am a contractor myself, and am familiar with concrete but only in footings and foundations. Help me out please, I want to do this in my house.