Greenbrae Chair Design

Time: 01:19

A video transcript featuring Fu-Tung Cheng, Cheng Concrete

This project demonstrates the design possibilities of CHENG D-FRC lightweight concrete. Here you can see how thin and how stable and how tactile this concrete can feel, and yet it has the properties of steel in that its tensile strength allows something as thin as this to be made.

As you can see by this project, this 1-inch profile, we didn't have to pour some massive block to get the same structural strength you would with ordinary concrete. That gives limitless possibility for all other projects that you may have in mind, such as benches, or a fire pit, or stools. All these products can be made out of the D-FRC. CHENG D-FRC is available in a whole palette of colors, and the plans are available online (

Greenbrae Chair Forming and Mixing

Time: 08:00

A video transcript featuring Mike Heidebrink, Cheng Concrete

What we have here is the Greenbrae chair mold. We've already assembled the project, but I want to go over some of the details before we actually begin casting it. First off, it's upside down. These are the front and back legs. This is the top, and this is the seat. We're going to be casting it upside down, starting by spraying into the mold, and then the final stage is where we'll actually be laying material up.

Greenbrae Chair Spraying and Casting

Time: 05:24

A video transcript featuring Mike Heidebrink, Cheng Concrete

What Clay is doing is actually starting on the wall, spraying into the corners. The reason for spraying into the corners like this is to make sure that we get wet material back in those corners, and not dry sand. There's a little bit of sand that's being kicked up in the spraying process, and we need to make sure that we don't get that sand trapped into those corners.

Greenbrae Chair Mixing and Casting

Time: 06:12

A video transcript featuring Mike Heidebrink, Cheng Concrete

We've finished spraying the mold with the casting blend and we've let it sit for about 15 to 20 minutes. At this point, we're ready to get going with the backing blend. The backing blend has a much, much, stiffer consistency than the casting blend. The casting blend, if you remember, was thin enough and watery enough that it could actually be sprayed through a gun. Unlike this material, the D-FRC backing blend has got a lot more fiber so when we blend it, it's going to have a consistency almost like clay, which makes it easier for us to actually lay it up the wall in consistent layers were it won't slump down off the wall.

Greenbrae Chair Demolding

Time: 02:23

A video transcript featuring Mike Heidebrink, Cheng Concrete

Our chair has now cured overnight and we're getting ready to demold it. But before I get into the actual demolding of this, I want to talk a little bit about some things that I've done to this before now.