Good design saves you time and money. “Water finds a way” is the maxim by which we should be guided. Water finds a way in through poorly considered cheek walls positioned at the bottom of massive valleys(as in the picture below). Water finds a way in under windows positioned too closely to cheek intersections. Water finds a way in behind siding and trim when the roof has a negative overhang. Snow finds a way in ridge and gable vents facing drifts in windy areas. It finds a way to crush a roof built with too little timber and too little pitch.
The photo above is from a home which is less than a year old. The left side of the header supporting the rafters above is not even nailed to anything. On the right end, which you can plainly see, one member of the beam is a full inch shy of touching the rafter it should be nailed to. The whole structure sits atop a dormer wall plate jutting out over absolutely nothing, and if the dormer walls are bearing any weight, they are transferring that weight to OSB plywood in the middle of an open joist bay. This is a brand new home in a neighborhood of approximately 3/4 million dollar homes. I've recently hired a structural engineer to evaluate it. This is lowest bidder work. This is what you get with many builders who compete for square foot residential pricing. How will you know if your builder did it right?
At least someone appreciates it!
All these calamitous and nagging problems aside, the roof is a visually impactful aspect of the overall
design. Too many angles can look downright disturbing. Mismatched angles can create a sense of vertigo. Additions, shoehorned in to existing architecture also can be striking in an unhelpful way. Remember that your roof is number one protection against the elements, but it is equal parts art and architecture and should avoid clashing with your existing design. Beauty is often the first victim of budget cuts, but often ugliness is the most lasting contribution to a neighborhood or individual property.