Brick Slips: The Death of Brick?

This is one of the largest brick buildings in the world, and it isn't a real brick. This is built as the tallest brick-clad building in Europe, and it isn't brick either. And those two are fake in completely different ways. And this one is built the same way as the first, which is the only reason it can look like this. A pattern like this is virtually impossible to lay by hand. So how was it built? Here's the thing. The brick on the outside of a modern building hasn't held anything for up to over a hundred years. And it has been getting thinner the whole time. It used to be almost two meters thick, then 10 centimeters, now two and a half. And as we are about to see, some modern brick-looking buildings have taken it all the way to zero. We have studied more than 20 ways of making a wall look like brick, and the best one we found had no brick in it at all. I'm Eugene Korch, I run the Façade Design and Engineering program at the Institute for architectural science and technology, and I've spent 20 years engineering walls like these. Let's find out what happened to brick. For most of history, brick was the building. Stack enough of it, and it carries everything. The floors, the roof, the people inside. But there is a limit. This is Monadnock building in Chicago. Built in 1891, 16 stories, and often called the tallest load-bearing brick building ever built. It carries its own weight, and its walls at the street level are nearly 2 meters thick. any taller, and the walls would have eaten the building. Two years later, the same owner extended it, and the new part has a steel frame, and the brick on the outside is just a thin skin. Same building, same brick, and that's the moment the brick stopped holding the building up. That skin settled into the wall we still build today. A single outer layer of brick, 10 centimeters thick, a cavity behind it, then insulation, then real structure. In frame buildings, that brick sits on the steel shelves bolted to each floor. It holds up nothing but itself. So what does it actually do? Well, two jobs. Keep the rain out and look like brick. It's wallpaper. Very heavy, very slow, very beautiful wallpaper. Around 200 kilograms per square meter of it. And it is expensive wallpaper. A brick layer lays about one square meter an hour. In the rain, work stops. And below three degrees Celsius, work stops too. That is mortar limitation. Mortar needs time to cure. If water in it freezes before it sets, it expands and breaks the bond. So the brick layers go home. Clay is fired at around 1000 degrees. A traditional brick wall on a steel frame comes about 98 kilograms of CO2 per square meter. Keep that number in mind in your head. Everything else in this video gets measured against it. So for the 20 years, the construction industry has been quietly answering one question. If brick is just wallpaper? What's the lightest, fastest, lowest carbon way to make wallpaper that looks like brick? The first answer is obvious. Use less brick. A brick slip is a real clay brick with the back sliced off. 10 centimeters becomes two and a half. And it isn't stacked anymore. It's hung. The weight drops from 200 kilograms per square meter to about 60. That changes more than the weight. A stacked wall can only be supported from underneath. A hung one can be fixed anywhere. Brick can go upside down on a soffit, it can wrap around the curve, and because it hangs off the frame, that frame doesn't have to be built on site. You can make the whole wall in factory and lift it into place. Which is how these three buildings were done. The tall one hangs its slips mechanically on rails, on factory-built curtain wall panels. Each panel arrives finished and gets craned up a floor at a time a power station is precast concrete slips go face down in the mold concrete is poured on top and the brick is locked into precast panel different methods very similar result from the street and the third one is precast too which is where it gets interesting brick bond that overlapping pattern exists for a structural reason overlapping the joints spread the load so the wall doesn't split but when the brick is cast into concrete it isn't carrying anything. The pattern stops being engineering. It becomes graphic. You can draw anything. And here's a tell you can look for yourself. A real brick wall needs vertical movement joints every six to nine meters. A soft line of ceiling so the wall can expand without cracking. Once you know, you'll see them everywhere. Now look at this building. They aren't in. Here's how. The whole facade stands on its own foundation, and it's only tied back sideways to the steel frame of the building. And at every junction between precast beams, two slips are left out in the factory and fitted on site, so the pattern runs straight across and there is no joint to see. Slips can be installed two to three times faster than bricklaying, in weather that would send bricklayer home. Thinner slips, same look, less of everything. So why isn't this the end of the story? Because the moment you stop stacking brick, you have to hold every single one of them by itself. In real brick wall, no individual brick can fall out. It's squeezed by its neighbors and pressed down from above. A brick slip is on its own, so the only question that matters is what's holding it. Across all systems we studied, there are only four answers. Hooked, cast, mortared, and glued. And they are not equal. Hooked means a groove in a slip locks onto metal rail. To get it off, you'd have to break the brick or break the rail. Cast means that the slip is locked into the concrete, with the key cut into the back of the brick that concrete flows into and grips. Neither of those needs glue to hold for 60 years. Mortared means that the slip sits between stainless steel teeth and mortar is pumped into to bond it all together. The steel holds the mortar, the mortar holds the brick. And glued means exactly what it sounds like. No rails, no key, no backup. If the glue goes, the brick goes. And glue does go. Water gets in behind the brick, it freezes and expands, it thaws, summer heat stretches the joints, winter shrinks it. There are published safety reports of slips falling off occupied buildings after 10 to 15 years. Brick slip weighs around 700 grams. Drop it from the sixth floor and hits the ground at around 70 kilometers an hour. That's enough to go through a car windshield. Then there's fire. In the UK, on residential buildings above 11 meters, everything in the external wall has to be essentially non-combustible. Glue is combustible, so are the foam-backed panels. On most blocks of flats above four stories, those options simply don't exist. And now here's the argument you hear from almost everyone who sells brick slips. You've replaced 10 centimeters of brick with two and a half, so you've got seven and a half centimeters more room for insulation. Same wall thickness, warmer building. Sounds obvious, so we've tested it. Quick explainer. A U-value measures how much heat leaks through the wall. Lower is better. A traditional brick wall with 20 centimeters of insulation 0.18 brick slips on rails same total wall thickness 26 centimeters of insulation 20 percent more 0.19 more insulation worse thermal performance the reason is the brackets to hang the rails metal brackets have to punch straight through the insulation and metal leaks heat aluminum especially so those brackets can account for up to quarter of all heat loss through the facade so the external insulation you gain by thinning the brick gets eaten by the hardware you need to hold the thin brick on. So we took more than 20 systems, built them all in the same wall thickness, and measured everything. Heat loss, weight, fire, carbon, lifespan. And the result that surprised us most was this. The wall with the best insulation performance was also the wall with the lowest carbon. Same wall, best at both, and there is no brick in it at all. It is insulated render. In the US you call it EIFS. A thick layer insulation a measuring force coat on the top and finish coat pressed with the brick pattern while it's still soft, U-value 0.15 the best in the study 73 kilograms of CO2 per square meter against 98 for real brick, the lowest in the study it's also the lightest and the cheapest and as long as the insulation is mineral wool it's not combustible and the reason is almost embarrassingly simple almost the entire wall is insulation and nothing punches through it so no brackets no rails no shelves so is that the answer not if you look up to one at two meters you can see it every brick is the same color every joint is the same depth and it cracks and it stains back again into it and you are patching not replacing and it doesn't last anywhere near as long so over the life of the building you may build it more than once but there is another way of doing this the same trick in something tougher pour colored concrete into the rubber mold shaped like brickwork and you get solid panel with the joints texture and the color cast straight into it no brick nothing to fall off in traditional precast those panels are thick heavy often up to 15 centimeters that's a lot of concrete and precast is the highest carbon system in our whole study but make it glass fiber reinforced concrete and the panel can be as thin as two and a half centimeters, a quarter of the weight. And thin, light concrete is that what makes the impossible possible. A 1960s office tower in London was extended by 13 stories on its original foundation. The new facade uses precast panels just seven and a half centimeters thick with brick slips cast into it. A brick facade like that would never have been possible in real brick. But here's what 20 years of practicing in the industry has taught me. Whatever the numbers say, people want real, natural material. Architects want it, clients want it. And everything I just showed you is, in the end, a very good imitation. It's fake. It isn't natural. With one exception. Take stone, cut it into the size of a real brick, and lay it by hand exactly like a brick. No slips, not a panel. A real stone wall stacked and bedded the old way. A real natural texture. There is one standing in Earl's Court in London right now. Stone isn't fired in a kiln. It's quarried and cut. 75 kilograms of CO2 per square meter against 98 of brick. About quarter less. The same insulation performance, non-combustible, centuries of track record. And because it's stacked, not hung, there is no glue to fail and no brackets punching through the insulation. There is nothing to fall off. It isn't perfect. It's expensive and it's slow to build as brickwork because it is brickwork. But if you want a natural wall that looks like brick and costs the planet less than brick, it doesn't have to be brick. So are the brick slips the death of brick? No and yes. Real brick is still the best option on buildings up to about 3 stories. It's workable up to about 12. It has centuries of evidence behind it and the biggest workforce that knows how to build it. Nothing else in this video can say that. Except perhaps stonemasonry. And brick slips haven't been around long enough to prove themselves. Modern slip systems are only a couple of decades old, and there is documented evidence of glued slips failing within 15 years of construction. But brick hasn't been in the building for more than a century. Two meters, ten centimeters, two and a half. And now, on some buildings, no brick at all. Brick slips didn't kill brick. Brick has been getting thinner ever since the Monadnock building, where it was as thick as it would ever get. And the best-performing wall we measured is the one where that number reaches zero. The full study is linked below, a 20-odd systems, every number and the drawings and the 3D details for each one. And if you want to learn to design these facades properly, that's exactly what our course at IST is for. Now I want to hear from you. Will the real brick survive or will brick slips replace it completely? Do you trust them? Let us know in the comments below.