Yes, I know it might not be practical to do this without errors and there’s reasons like running utilities through and quality control with inexperienced workers, but technically speaking, could you make stronger structures with less materials using stronger structural shapes? Maybe it’s just more pleasing to our eyes everything being straight and square and such, but what about utility canopies and tents where you want to have your structural members as light and portable as possible? Why do we not have tetrahedron shaped tents that have 3 small, collapsible, yet rigid poles and a firing they go in at the top instead of having long flexible ones?
In: Engineering
The strength that a diagonal joist would add would be strength against racking of the structrure when viewed from above. Essentially if you had a square house, it would resist a force that was trying to move parallel walls in opposite directions, like trying to turn it into a parallelagram.
But in reality there are not really many things that are going to apply that sort of force to the structure. A wind is going to hit an entire side of the buildilng pretty evenly. Nothing is really going to be pushing on one wall with a force that is parallel to that wall.
Its more important to deal with racking on the vertical walls where you have a pivot at the bottom created by where the wall meeets the foundation. In that case, wind blowing on one wall will create a racking force in the two perpedicular walls as the leverage from the wind tries to blow the wall over.
The force a floor has to deal with is downwards force on the floor itself. A triangle laid flat isn’t going to help with that.
The reason you see decks with diagonal decking is because often times they are very far from the foundation and anchored to the house at one end. In that case, you can get a racking force because it pivots at the house and the force the foundation exerts is pretty limited because it might be on tall supports.
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