An alternative to casting a solid concrete countertop, anyone with experience?

[HSV1]

I have long been planning to test cast kitchen countertops in concrete but have realized along the way that there are alternatives that might make the process somewhat less cumbersome. What I've been drawn to is "spackling" the concrete instead of casting it completely. The approach would be something like this:

1. Saw and glue together OSB boards to the desired size and thickness.
2. Router out holes for any sink/hob.
3. Spackle fiberglass mesh on any seams, or on the entire board; this is to prevent cracks in the concrete when the wood moves.
4. Apply a primer so the concrete adheres.
5. Spackle on concrete. Repeat 1-2 times with 12h+ in between.
6. Finish it as desired. In my case, probably with Steinfix 100, without any sanding or wax.

I am thinking of making a smaller version for now. If anyone has any tips, tricks, or warnings, they are welcome!

All the best! /HSV

 

[HSV1]

I imagine that one should add a layer of plastic somewhere as well. What and where I am more unsure about. Anyone with suggestions?

 

[vectrex]

Doubtful that you can putty concrete in that way and achieve a durable result?

 

[eviljava]

For a long time, I have been planning to test cast kitchen countertops in concrete but have realized along the way that there are alternatives that might make the process somewhat less cumbersome.

Frankly, I thought your putty method seemed more cumbersome than casting in the usual way. Besides this, strength and finish are something I doubt you'll get with your method.

But it would still be fun to see the results of the "prototype," as well as some pictures from the experiment.

 

[Krille4]

Interesting setup, but is it really easier or better than casting the countertops?

/Krille

 

[JoakimJohansson]

I can imagine you save some weight this way as well!
Sounds interesting... Don't you need to reinforce it in some way with like fiberglass or something?

 

[HSV1]

Doubtful that you can spackle concrete in that way and achieve a sustainable result?

I am also doubtful; but curious. I am trying to find out how the mixture should be; because mixing fine concrete in the usual casting way is obviously not relevant here. I got the idea primarily from this guy: http://www.unt.se/blogg/blogg.aspx?blogg=485369
Scroll down to see his results.

Honestly, I thought your spackling method felt more cumbersome than casting in the usual way. Besides this, strength and finish are something I doubt you achieve with your method.

Yes, well, I am inclined to agree that this is still cumbersome. I imagine it might help in the way that you are constantly allowed to measure/correct/work with the board in place in the kitchen and on the frames; and that altogether it is a quicker process.

Interesting setup but is it really easier or better than casting the countertops?

/Krille

That remains to be seen if it is easier. It probably won't be better; but hopefully good enough.

I can imagine you save some weight this way too!
Sounds interesting... Don't you need to reinforce it somehow with something like fiberglass or something?

From what I've read, you've only reinforced the joints. But I also think it sounds reasonable to reinforce the whole thing.



But I am a bit worried about how the wood works together with the concrete. It feels like there must be a protective layer against moisture? Maybe there is some other base material to work with instead of OSB?

 

[Helioz]

You could make the board as a horizontal facade instead. Then you build the frame from EPS foam boards which you glue at the seams with polyurethane glue. Then you apply a layer of 8mm A-rated glass fiber mortar, which you also reinforce in the middle with fiberglass mesh/facade mesh. Finja has a good mortar:
http://www.finja.se/App_Resource/Product/PDF/PB/5585032-1.pdf#view=fit

The board can then be puttied with concrete filler or surface-treated directly depending on the appearance you want.

Glass fiber mortar is commonly used to make concrete slabs in the USA where it is sprayed into a mold; the method is called GFRC if you want to google it.

 

[HSV1]

Thanks for the tip, I'll take a closer look at it!

I'll update the thread when the project kicks off!

 

[jeppeknaster]

http://www.decomaterial.se/web/start

There you have the material. Look in the image gallery. No problem having wooden boards.

 

[HSV1]

Yes, that's what the guy in the blog used. However, it's not really feasible at that price! On the other hand, it shouldn't be impossible to experiment with something like kalkcement C?

 

[jeppeknaster]

I think it costs about 300kr/m2. It doesn't become too expensive if you only have a countertop. Better that it's done well and costs a bit more than being cheap and cracking

Google a bit on Perfectino or béton ciré, and you'll find quite a bit.

Here you can see how flexible Claystone is: http://www.youtube.com/watch?v=R-R2bJctNyQ

 

[Helioz]

Keep in mind that an elastic material can never be hard. These types of lime plasters are great for decoration but relatively sensitive as countertop surfaces. If you drop a heavy pot or drag a cast iron skillet slightly askew on them, the surface can both dent and scratch. The same goes if you drop sharp knives. In hardness, it is comparable to a wooden countertop.

This is somewhat confirmed by the fact that the compressive strength is not listed on either the retailer’s or the manufacturer’s websites, making it impossible to directly compare with concrete. But since it doesn't contain cement, it's probably comparable to Kalkbruk E which has a compressive strength of around 1 MPa compared to fine concrete which has 40 MPa.

It also requires that you are careful with the surface treatment and maintenance, otherwise water can penetrate the thin lime layer and cause the MDF or particle board to start swelling and ruin the countertop.

 

[jeppeknaster]

I think you can treat the surface with Osmo hard wax oil