This arched window is a shocker.
The arch is one of the most basic structural forms being simple and exceptionally strong.
Besides the curve of the arch the basic principle is the arch springs from a solid support, like this example to the right.
The first window has the arch supported by two cantilevers from the sides of the opening. In reality a complex structural form that is much weaker than the simple arch.
I think that for a normal domestic house simple arches or straight beams are the only way to go.
For more Fails and Unusual houses go to What the………………….?