Why Do Architects Insist on Using Flat Roofs?

It is a commonly held belief by non-architects (and even some architects) that gabled roofs are inherently better than flat ones. The argument typically goes that a gable demonstrates a ‘form follows function’ sensibility, easily shedding water and snow using geometry and gravity. So, flat roofs might leak. While that’s true, this video blows the roof off the topic by taking a finer look at some points that might change your mind. This includes Louis Sullivan’s original reason for writing the phrase “form ever follows function,” as well as the ability of flat roofs to offer outdoor public spaces, supporting green roofs, structural simplicity, wind considerations, among many others. There’s also another, competing functional/formal reason for why a low slope roof might be more prudent than a more aggressive slope, even in snowy areas like Chicago.

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Architecture with Stewart is a YouTube journey exploring architecture’s deep and enduring stories in all their bewildering glory. Weekly videos and occasional live events breakdown a wide range of topics related to the built environment in order to increase their general understanding and advocate their importance in shaping the world we inhabit.

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Stewart Hicks is an architectural design educator that leads studios and lecture courses as an Associate Professor in the School of Architecture at the University of Illinois at Chicago. He also serves as an Associate Dean in the College of Architecture, Design, and the Arts and is the co-founder of the practice Design With Company. His work has earned awards such as the Architecture Record Design Vanguard Award or the Young Architect’s Forum Award and has been featured in exhibitions such as the Chicago Architecture Biennial and Design Miami, as well as at the V&A Museum and Tate Modern in London. His writings can be found in the co-authored book Misguided Tactics for Propriety Calibration, published with the Graham Foundation, as well as essays in MONU magazine, the AIA Journal Manifest, Log, bracket, and the guest-edited issue of MAS Context on the topic of character architecture.

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[DUNGEONCRAFT]

I am not architect and I have no idea why the YouTube algorithm recommended this video to me, but it was fascinating. I've never paused to consider why the roofs of tall buildings are flat, but now I know. Great job!

[sparkster]

Biggest problem in my field of work. The ability of a flat roof to retain every ball that school kids get up there.

[gpower]

Ancient Egypt and Mesopotamia are famous for their lack of snow and low precipitation, similarly people mostly complain about flat roofs in places with a lot of rain and snow. I’m from MN and had a flat roof high school and after major storms they had to send the janitors up to shovel off the snow. And they were terrified to allow the flat roof to be used as a public space lest a kid fall off- it was a 1 story building.

[vulbyte]

i actually wanna add as an ex-roofer;
flat roofs are generally much easier and faster to repair/replace. and some large commercial buildings have taken the same amount of time a residential House has, dispite being 1/4 or less the commercial buildings size.

[jbaidley]

I don't know about elsewhere, but in the UK flat roofs in a domestic setting are synonymous with shoddily built extensions that are cold in winter and have persistent leakage problems ten years after they were built. I think it's this that leads people to loathe flat roofs in houses.

[ruki]

As someone living in the desert, I can understand why Egypt and mesopotamia used flat roofs: not alot of wood, not a lot of rain. I just sorta assumed those are the two conditions for using flat roofing.

[IznbranahlGoose]

I've seen examples of large buildings with sloped roofs and how areas near them have to be blocked off in the winter to prevent people from getting clobbered by falling sheets of ice and snow.

[johnbuchanan]

Additionally lots of single family neighborhoods, especially view and small lot neighborhoods, have building height limits. Having flat roofs maximizes interior space and allows building out to the height limits.
Great topic!

[SakraIgorqNomoko]

As someone who lives in an area with plenty of snow and wind, I occasionally hear about buildings with flat roofs collapsing due to snow load and shingles or entire buildings with shingled roofs being blown away, such as my old neighbor's garage. Debris comes on the wind, breaking a few shingles, then the wind catches the roof, blowing the whole thing apart. For me, it's sloped metal roofs all the way.

From this video, I better understand the reasons for having flat roofs, besides just cost. One point that was not brought up, however, was the time of year they need maintenance. Sloped roofs need gutter care in the spring and fall, but flat roofs need shoveling in the dead of winter, which where I live is wind season. I ain't gettin' on a flat roof to shovel 3 feet of snow in 70 mph winds at -20 F, that's for sure.

There's definitely people around that'll do the job for the big bucks, 'cause I've seen 'em work on flat-roofed businesses, but I don't get paid "have someone else risk their life" kind of money.

[Abornarazine]

The biggest problem I saw in property managent is that building with "Low sloap" roofs, didnt have a slope at all. It is critical that the roof actually have a sloap. The one building i had the pleasure of helping managing/maintain that had a 6° sloap never had problems. The roof was in fantastic shape, and you could tell by stepping foot on it.

Sure did it feel a bit weird if you stood on it? Yeah, bit it shed water and snow like a champ, while still giving the high rise a place to store unsightly machinery.

[ulexite-tv]

I bought a two-story Victorian farmhouse that had a flat root extension on one end. It leaked. We had it reroofed twice, and it still leaked. Then we built a gable roof over the flat roof. We now use the resultant triangular space for storage and the gable roof doesn't leak.

[kentrichardson]

Glad you addressed this subject. I’m a small time retired contractor who mostly did small renovations and repairs. There is a huge disconnect between designer and product years after the build. I live in the Pacific Northwest in what’s described as a temperate rain forrest. I’ve seen many “fails” due to form before function. On large buildings, flat roofs with steel truss systems make sense. On residential buildings in my climate, flat is a poor choice. Any flat roof I’ve ever been on will always have pockets of standing water on it which shortens the life of the roofing material. They are also highly dependent on maintenance. Built in gutters, drains, scuppers, all need cleaning and MOST homeowners neglect regular maintenance. These transitions also are “ week spots” at the time of build, relying on proper installation techniques and skill. The disconnect is 20-30 years down the road when that flashing has failed and rotted out the wall, and siding, the designer will never know that a part of his or her system failed and is now a costly repair. With building as well as roads and outdoor structures, channel that water away from the buildings as fast as you can. Don’t rely on materials and caulking, they will fail. Choose building materials and design suitable for the climate.

[Shipx]

Imagine an ice build up on a sloped roof breaking off and falling 10+ stories. I think flat roofs for big buildings makes sense.

[selanryn]

My high school in Texas had a flat roof that collapsed after 20 years due to water accumulation. It was a small district and there was nowhere else to send kids while repairs were made, so we just had to attend classes while the school got re-roofed. Good times.

[Throwaway]

I'm a home inspector, recently graduated from a class. That class pretty much took a giant shit on flat roofs. I sincerely appreciate you putting together this video and explaining the benefits and the trade-offs that both types of roofs have. Thanks so much.

[jonachs]

As someone who designs very large warehouses, a flat roof is really the only option as you say. That said, scuppers are awful, and I much prefer dedicated secondary drains down to grade. I appreciate your simple explanation of the systems.

EDIT: also, these designs in large warehouses are typically dictated by the structural engineers and G.C.s to keep costs down.

[monwell]

Your channel is slowly reinventing my passion for architecture. Was my major in college, but lost my way once working, and have since moved to another industry. Maybe it’s time for a second look. I could only imagine what it would be like to have a passionate prof in class. All of ours tore us down and never helped shape design.

[MTips]

As a commercial roofer, this is one of the best videos explaining their purpose. You really didn't miss a thing.

[widehotep]

My experience is that the shingles on a gabled roof usually show obvious wear before they leak, giving the owner a visual warning that the shingles should be replaced BEFORE the home is damaged by water. But flat roofs are hidden from view and don't show obvious clues before leaking. Water just starts dripping in one day. The leaks are tricky to fix because the source of the leak can be twenty feet or more away from where the water drips in.

[gabrielvilela]

In Brasil, flat roofs are also a afordable solution for limited access to land in most major cities. On the top of the houses, it became a space for gathering and leisure, making itself very present in the emotional and cultural landscape of working classes throughout the country.