We do a little destructive testing and have a good breakfast.
August 24 is National Waffle Day in the United States, honoring the day in 1869 when Cornelius Swarthout of Troy, New York, received his patent for the waffle iron. This is distinct from Våffeldagen, or Swedish Waffle Day, celebrated on March 25. Readers often think I'm nuts, making such a big deal of waffles twice a year; it's because it's an opportunity to show all my photos of waffle slabs, a form of concrete construction that isn't done that much anymore. It's a shame, because there is a lot to learn from waffle slabs. (Also, I get to have a nice breakfast.)
A regular concrete slab is just a slab, and the longer the span, the thicker it gets, to maximize the distance between the reinforcing on the bottom and the concrete in compression on top.In a waffle slab, you take out all the concrete between the reinforcing, leaving it in ribs. So you get the depth and the long spans without nearly as much concrete. Flat slabs are also boring, so they tend to get covered up in drywall. Waffle slabs are designed to be exposed, to be seen, to say, "Look what I can do, so much with so little concrete!" Less truly is more.
This National Waffle Day, I thought I would demonstrate the principle with my breakfast. At the top of the post you see two upturned blueberry boxes and the waffle sitting there nicely with no deflection at all.
Then I started piling on plums for destructive testing. It laughs at two plums.
I got up to four plums. It is clearly on the edge of collapse with the bottom breaking, but the ribs in compression on top are still fighting back. There was no room for more plums and I couldn't wait; I was hungry.
The limp and formless pancake, on the other hand, can barely hold up its own weight and is sagging already. It's ugly too, compared to the crisp and defined waffle. To be fair, it is hard to reinforce a pancake. I was thinking of lining up some green onions in a row and making reinforced scallion pancakes and might try that next waffle day.
The pancake went and pancaked with just one plum and didn't last long enough to get a photo.
Some people say that we should just stop using concrete in buildings and pick low-carbon alternatives like wood. Others, like Paula Melton at BuildingGreen, say it's more complicated than that, that we should "consider which materials and systems make the most sense for the project, and optimize how you use them"
After a lovely breakfast of blueberry waffles (and thanks to mixer, pourer and formworker Kelly Rossiter), I will again make the case for what I learned from engineer Nick Grant and call Radical Simplicity: to start at the beginning by designing things to use as little of these materials as possible, whatever they are.
That's why I celebrate tasty waffles, even when they are made out of concrete, for those spans that go on forever using as little material as possible, and not too proud to show off about it. If you've got it, flaunt it.
My favorite waffles
Every year when I do this, people complain, "You forgot this one or that one." So this year I am cutting the rest of the post back to only those waffles I have seen and photographed myself.
My favorite waffles are at the Montreal Museum of Fine Arts' decorative art collection in the Liliane and David M. Stewart Pavilion. Unusually, the ceiling is really low so the span feels magnified, and you can get really close. I had trouble looking at the fabulous stuff in the museum because I was entranced by the ceiling, layers of the tastiest waffle slabs I had ever seen. The entire structure is there for you to see: nothing but the concrete that is holding itself up.
It's like that at the Barbican in London, where they have turned each cell of the waffle into a light fixture.
Waffles are dramatic high up as well, as shown in the Washington Metro. The trains may not be holding up so well, but the roof certainly is. I did not originally think of this as a waffle slab; I thought of it as a coffered ceiling. But others do not waffle about it, so here it is.
There are wonderful waffles at the National Theatre in London.
And really cool ones at the Confederation Centre in Charlottetown, Prince Edward Island, where in one section, they even left off the slab itself and put on great pyramidal skylights.
Nervi got nervy with concrete waffles at the FIAT Factory in Turin, way up at the top of the ramps.
On this Waffle Day, spend some time looking up at ceilings. You will see few as beautiful as those waffle slabs, few that have lasted so long. They are at once decorative, structural (though this one by Marcel Breuer at the MET Modern is totally decorative, hanging below the ceiling), and durable, all attributes of green building.
Are there waffles you love? Tell us in comments!