Concrete counter-tops

April 25, 2005 4:53 PM

I'm thinking of building my own kitchen counter-tops from concrete. I have some how-to books and have talked to a friend who is doing it as well, but thought I'd put the question out to AskMefi. What has been your experience? Any tips or tricks? Any special materials or sealers? Thanks!
posted by jacobsee to home & garden (11 comments total)

I can't think of any brand names off the top of my head, but I recommend that instead of an epoxy finish, you use a penetrating sealer and then a few coats of wax.

Incidentally, if you're thinking of staining the concrete before sealing it, have someone with experience do it. (I've had a couple of inexperienced contractors royally screw up floors with their stain job.)
posted by Specklet at 4:58 PM on April 25, 2005

The Journal of Light Construction just had a large article on concrete countertops.
posted by Myself at 5:26 PM on April 25, 2005

omg, totally go for it. you will be amazed at what you can do with concrete, and how smooth of a finish you can achieve, especially if you get a variable speed grinder and some diamond resin pads.

have you come across cheng's site yet? this is a great place to start, along with his book.Cheng's concrete exchange is a great resource for looking at examples, and ordering products. get his book concrete countertops if you don't have it yet.

I don't know where you are with learning about this, so I don't know how specifc I should be with the tips I have come up with.

Simply put, make molds out of melamine, seal corners with *black* caulk (made for blacktop and asphalt - white painters caulk is harder to see against the melamine and *i think* reacts with concrete), mix concrete (i use sakrite 5000), pour, vibrate (build a platform to put the mold on and vibrate from underneath with the side of a sander), cover, and let sit.

Let me know on which sections you want me to get into more detail.

An example of what I've done in my house can be found at the end of my "project 1" flickr set.

(If you look at my "project 2" you'll see a desk (and subject of former 'ask' thead) for which 3 molds (including my first non-rectangular mold) are being made now.)
posted by ArcAm at 5:44 PM on April 25, 2005

we have a couple of coffee tables which are concrete slabs that rest on metal frames (so the legs support a kind of holder that the concrete slab sits on.

they seem to be made from a very fine cement by being cast in a mould made from a sheet of plastic (you can see the plastic folds at the corners). and the concrete has been poured in two contrasting colours, so there's an amorphous central blob.

they are amazingly cool. i have to dash for a conference dinner now, and have no ethernet in my hotel room, so email me for more details if you're curious. unfortunately, they're hand made in chile, and expensive, so i doubt you'd want to buy them.
posted by andrew cooke at 5:55 PM on April 25, 2005

I had some architect friends who did this several years ago in a house they were sharing, and it came out very, very cool. While it definitely helped that one of them had worked construction a lot for summer jobs, etc., and had become something of an expert on doing concrete, I don't think it was especially complicated to do.

One thing I do remember, though, is that they did the epoxy finish thing too, and the final color came out _totally_ different than they expected. They thought it would just form a clear resin coat over normal-looking grey concrete, but instead, it made the concrete look "wet", and the whole thing came out more of a darkish-olive-green. In the end, it still looked great, and they just made believe it was on purpose, but it was definitely a surprise.

It may have just been a timing thing, where the concrete didn't cure enough, or it may have been the specific type of epoxy they used, but you might want to experiment with the specific setup you want to use, first.

Oh, and one final thing--I know this seems kind of self-evident, but _don't_ underestimate the final weight of the thing. Make sure you've got the structural support in place up front to really handle a few hundred pounds (or more) of weight.
posted by LairBob at 5:56 PM on April 25, 2005

A friend loaned me a book on fabricating concrete counters, here's the Amazon page.

I just realized it is the above mentioned book. It really is quite information packed, well-illustrated, etc..

And my only advice:

When working on jig and/or mold based projects, hold yourself to the higest standards in all prep and setup work, panic produces poor decisions.
posted by Jack Karaoke at 6:02 PM on April 25, 2005

Amen on the high standards.. Any imperfection in the molds will show in the concrete. Molds should pretty much be furniture grade.

re: color and finishing. there are two options for sealing: penetrating and topical. topical might not be the best choice for a kitchen because it'll peel off if you set down a hot cooking tool on it. penetrating, otoh, won't, but it will take stains.

polishing or grinding will likely take the color of your concrete a few shades darkers, and topical epoxies will look plasticy or wet, yes.

with concrete you've gotta realize that it will always be a working document of sorts, changing with time, developing a patina, and recording a history.
posted by ArcAm at 6:13 PM on April 25, 2005

Don't they develop hairline cracks over time as well?
posted by LarryC at 7:43 PM on April 25, 2005

hairline cracks can develop over time, tho the seriousness of them can be abated by putting wire lathe (or rebar) in the concrete. cracks can be prevented with admixtures of things like fiberglass. if a crack got bad enough (aesthetically), a slurry* could be made out of pure portland cement, water, and dye, to patch it up. AFAIK, if the countertop is supported well enough, if cracks occur, it isn't a structural issue.

*this is also used to fill in any voids that appear in the concrete after the first time it is ground (polished). it isn't easy to vibrate the concrete to get all of the air out, so often the bubbles will leave small pock marks on the surface. if there are many such marks, a contrasting colored slurry can be made for an interesting effect.
posted by ArcAm at 8:05 PM on April 25, 2005

I am looking into concrete counter tops as well and sounds like i'm in a similar boat as jacobsee. I have read Cheng's book front to back and agree it is full of good info. A couple questions though. He recommends using type II or type III cement. I can't find this anywhere!!! I've called around and looked at home depot and lowes and couldn't find it. Any ideas where to find it?
posted by retro88 at 9:08 PM on April 25, 2005

I think a slurry of pure concrete and very finely ground graphite would make a slippery non wettable metallic like finish when polished out I have not tried it though.
posted by hortense at 9:23 PM on April 25, 2005