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Hi,
I have read through a ton of archived postings (both here and usenet)
in regards to the forming/casting of concrete countertops, but what i
haven’t come across is people talking about integral drainboards
and what people have used as forms to create these.
once i get the hang of using concrete, i plan on attempting a kitchen counter
top in an inverted form. i have seen several pictures of cctops with the integral
drainboards, whether it be a continous slope such as this (although i prefer
a shorter slope to the sink)
http://www.chengdesign.com/images/Geo_pop4.jpg
or grooved such as
http://media.bigstep.com/shop/3/94/1050943/upload/1007513277658.jpg
I would assume for the grooved look, people might use half round trim
(desired width), cut it to the desired lengths and seal it. what would the best
way to attach the half round to the form so there wont be any seeps?
nail it? glue it? both?
as for the sloped drainboard, does anyone have any good ideas of a
wedged shape item that can be used as the form? i realize a piece
of wood could be shaped to get the desired depth, pitch and length
of the drainboard, but is this the best way.
basically i am curious to find out the creative solutions people have
come up with to create their drainboards. any thoughts would be
greatly appreciated.
thanks
oak
Replies
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I've never made one of these things but I'll bet you could attach your tapered half round strips with caulk, to the form, squish it down and wipe off the excess, let dry. If any slurry seeps out somewhere it should just scrape off.
*In precast work we used brads to fasten the half round and sealed the edges with silicone caulk smoothed with a finger. Caulk alone will hold it but it can be knocked loose if someone gets too wild with the vibrator. The silicone serves two purposes; sealing so the cement paste doesn't creep under the 1/2 round and providing a slight radius to the corners to reduce/eliminate chipping. We use MDO or HDO for formwork ....this will work fine for your wedge. You should build the wedge with a slight bevel or "draw" to the edges so you can remove it without boogerin' your concrete up. If you want perfectly straight edges, consider using oc pink or blue styrofoam for your form. You just break it up to remove the form. Foam works well for holes or openings, too.
*I'm afraid I've never formed one of these either. I have done quite a bit of concrete forming and even some decorative work and I agree with both of the suggestions you've received so far. I wonder though, what are you going to do as far as your sink? There are solid-surface material solutions out there that include one-piece sink/drainboard combo's. Gibralter and Surrel both offer these. I think Dupont does in Corian too. It's just a suggestion, but have you considered checking into them and integrating them into a formed concrete countertop? I've had this done with solid-surface and granite tops so I assume it would work with concrete. You'd have to stain your concrete to match your choice in drainboards, but since you'll probably be staining it anyway, or howeve you choose to finish it, that shouldn't be a problem. And it would make forming the concrete immensly easier.
*The issue of FHB that's at the printer as we speak has an article excerpted from Fu-Tung Cheng's forthcoming Taunton book that covers just this topic. Wait a couple of weeks and you'll have it.
*Andy, when will the book be released?
*Oak, First, I sent you the info you requested. I got a bit backed up, sorry for the delay.Personally, I think the sloped half-round grooves in an otherwise flat countertop look foolish. Most of what I've done is similar to the pic in your first link: An integrally sloped drainboard, with the drainboard either having half-round grooves, metal bars, or both. I prefer the metal bars, as they hold the pots off of the drainboard. I think they are more functional. They add a nice bit of visual texture ("visual texture?"...that may be the silliest thing I've ever written) to the countertop as well.I build an inverse image of the drainboard from wood, then cover it with gloss formica. It gets attached to the bed of the form by screwing through the bed of the form and into the drainboard assembly. The sides of the form are slightly sloped to facilitate removal after casting.For the grooves, I route half-rounds out of plastic...white plastic cutting boards, to be specific. It machines well and gives the cast concrete a nice surface. A thin bead of adhesive and a few brads to keep it from shifting while the adhesive sets will hold them in place.Metal bars can either be cast in as well...though it's too difficult to explain in words how I do that. They can also be added post-casting by cutting a slot in the drainboard with a diamond blade and epoxying the rod in the cut groove. I use stainless rods to match a stainless kitchen, as well as a few other metals depending on decor...brass, etc. Adding the metal does make the project a bit more difficult.When you make your drainboard form, slightly round over all "outside" edges. Sharp corners in the inside of the cast drainboard, while looking snappy, are stress risers. That means they are focal points for potential cracks.
*Fu-Tung's book is due out on 4/15.
*Metals bars in the bed of the slope is likely easier to keep clean and hygienic than narrow valleys. Less likely to crack and chip too. Two slight variations on the same method for installing them without using blades, etc:Instead of using half rounds attached to the casting bed, rout out the space in the form slope and drop in a sealed full size dowel-this will create the void for the metal to be glued into after you lift the cast. Alternatively, you could use the metal bar itself in the form and lift it out with the concrete cast. The first method has greater guarantee of adhesion however.HTH Jean-Paul
*I want to thank everyone for replying...as for the article in the next issue of fhb, im looking forward to it (i did like the idea of the concrete tub in this issue, but my girlfriend wasn't buying into it...)as for the book, i already pre-ordered it and i am looking forward to it.as for mongo, thanks a bunch for the document you sent (and all the previous archived posts, ive learned a ton over the past week readingover the stuff...)oak
*My 'sculptor's type approach to it would be to make a full size mock up of that area out of plaster. Use the metal bars, and anchor them in the plaster the same as you will want them anchored in the concrete.Let set up completely. Now, build a form around it. Smear everything in some sort of form release, vaseline, oil, whatever. Pour the form full, on top of the mockup.When that sets up, remove the form. Remove the last cast you poured. Turn that over, and set it in the upside-down countertop form, in the place the drainboard is to be formed.Now, break up the first casting, removing the metal pieces, and cleaning them thoroughly. Lay them into the cast that is in the countertop form, in the way that you want them to be in the final result. Don't forget to anchor those metal pieces to each other, and to the rebar mesh, so they don't get pushed around by the concrete when it is poured. It will be easy for the concrete to force it's way under the metal bars if you aren't careful. Man, I could get a real hoot out of actualy doing this.