If walls of ordinary houses were tilted inward ever-so slightly, would they be sturdier?
Just as a trapezoid is inherently sturdier than a square.
And thus as a corollary, could they be as sturdy as now, but cheaper, greener?
Why would they be? A house isnt a support structure for the roof, its a structure with a foundation first, some structural walls and a covering to keep out the elements. I dont see why your idea would make any difference. The design isnt crying out for more roof support.
Greener? You still chopping down trees to make the house and importing drywall from China. Cheaper? Im sure getting away from right angles right would make no difference or just add cost because its a differnet design than what contractors are used to.
Are you talking about all the walls, or just the exterior ones?
Are you talking about houses whose footprint is a square or rectangle, or more complex plans?
Are you speaking of single story houses or multi-story houses?
Do you figure “cheaper” on the basis of square footage of useable floor space?
I don’t think so. Vertical walls are pretty efficient, as they are designed to be loaded in one mode, compression. Shear walls or bracing are added as needed. Positioning the walls so they must take both vertical and horizontal loads is going to be less efficient.
Now I’ll wait for a structural engineer to point out that I’m wrong.
Egyptian (ancient) structures were built with sloping exterior walls. This was done to relive the outward thrust at the base f the walls.
This makes no sense.
I agree. The pyramids were not sloped until a cap stone for show was put on. I think you can use a lot less material and have more human space with a modern house.
Look to the A frame house that almost nobody constructs for a house with slanted walls. Slant the walls and lose human space by the walls, because you can’t fit there.
Which reminds me of a neat design I saw 30 years ago, give or take.
Imagine something like a mobile home, long and narrow. The cross section is squarish/rectangular.
Rather than have one flat side on the bottom, two on the sides, and one on the top, you rotate it 45 degrees, so that two of the corners are on the side, one is on the top, and one is one the bottom.
A bit odd, but one could argue that it makes better use of the volume ergonomically, particularly if the cross section is rather small in size.
I am not a structural engineer. That said: Um. A trapezoid without lateral bracing is NOT more stable than a regular rectangle, except for direct vertical loads. Skew those loads a little, and the vertical benefit goes away. Granted, this would only be important where there were any horizontal loads to be considered, such as seismic or wind loads. That is, pretty much anywhere.
The same lateral bracing would be needed, and the disadvantages would be in the added difficulty and cost of construction and loss of useable floor space.
billfish678, not sure I understand. What happens to the ceiling height? Tilted everywhere?
Right. And please let us know when you’ve designed a house made of a couple million stones weighing several tons each.
The logical result of this would be a geodesic dome structure, as patented by Buckminister Fuller 50-some years ago.
Triangles are the most sturdy form, and geodesic structures are made up entirely of triangles, so they should be much sturdier than either striaght or sloping box structures.
And when constructed as spheres or partial spheres, they enclose the largest volume with the least amount of construction materials, so they would be much greener.
But they aren’t cheaper, compared to the thousands of designers, architects, and construction workers experienced in building ordinary box structures.
When I built my own house, I canted the lower floor walls right up to the the windowsills of the upper story. It did allow for more insulation on the lower floor walls, and COULD have been structurally more resistant to lateral loads (like earthquakes, I live in California), but it was a cosmetic treatment, not structural.
The thing that makes it stronger is not a trapezoid, it’s the triangular exterior walls (the interior walls will still be vertical).
It does make the house appear to be more firmly planted and sturdier, which pleases the eye. But in my case it is fake. Still, it looks and feels great, allowing deep buttercut reveals on all the windows.
A lot of people think the roof conveys only a downward force, but it sends an outward force as well.
This is the problem Christopher Wren found when constructing his classic domes in London. He had to keep modifying the structures to add hoop stays around to keep the dome from pushing outward past the supporting walls.
Also, that outward pressure is what made designers of two story log cabins make the second story not line up directly over the first.
I was just about to mention domes. It’s a pity that Bucky’s dream hasn’t come true (yet) and domes never really took off. I find them fascinating and would like to build one some day although that seems a distant dream right now 
They’ve survived hurricanes where neighboring houses have been destroyed. I think that’s due to a combination of their strength and the fact that air goes around them. A big flat wall is not want you want when the wind is blowing. But you’re correct. The harsh reality of building a dome today is that they tend to cost more, are more work and require a higher degree of engineering skill than a conventional house.
Bucky often reminded people that there are no right angles in nature and the triangle (or tetrahedron in three dimensions) is the only structure that holds it’s shape.
Castle walls were often slanted (inward and outward) to make them more difficult to scale or to deflect projectiles. Do infidels lay siege to your neighborhood often?
ETA: They were also often slanted like the lower floor of sunacres’ house - thinning toward the top, making it harder for sappers to collapse them.
That’s what I say, man.
F the walls.
You’re right about that, but most homes are built so that the roof doesn’t exert the outward pressure on the walls. Instead, you often have cross beams that go all the way across the roof. These support the expansion force outward so that only a vertical, downward force is applied to the walls. (Much the same as the hoop stays you mention for domes, I would assume).
Ever live in an A frame? They have lots of issues with wasted space. Can’t push a chair or couch against the wall. Don’t get me started on hanging pictures or using a tall book shelf.
As far as cheaper, no way. Carpenters love 90 degree right angles. Anything at an angle takes a lot longer to fit properly.