Whether you're building your home from
cob, cordwood, papercrete or
wood it is advisable to give your home a substantial roof overhang to protect the walls from moisture and to keep unwanted mid day sun off the Windows. Yet many homes are built with very short, inadequate overhangs.
Sometimes ignorance or style considerations have been the
root cause of this common problem but in many situations the choice is made in order to satisfy economics and government regulation. In any
city which counts the overhang in setback requirements you'll find that in order to build to a given distance from property lines builders find it necessary to reduce the overhang. If you must stay back 20 feet and you're on a small lot, chopping back the roof line is usually the only way that the property can be maximized. I've seen this most commonly on small lots in areas where
land is very expensive.
Another issue which drives people to create an inadequate roof is taxation. If the roof overhang is considered part of the building
footprint and counted in the square footage then these overhangs tend to raise the tax burden for that home.
So in order to prevent homes from being built with inadequate overhangs, the square footage and setback requirements need to be changed so that builders and homeowners are not penalized for good practice. If overhangs were no longer considered in setback requirements and they did not add to the tax burden we would see a general improvement in home durability and
energy usage without changing one other thing about the house.
On the West Coast there has been billions of dollars worth of property damage due to the leaky condo issue. Although house wraps, vapor barriers, vinyl stucco, inadequate
drip edges and gutters and builder ineptitude were huge contributors to this problem, had these buildings been given substantial overhangs much of the water infiltration problems would have never happened. I'm fond of saying that if you build a large
enough overhang you can build your house from talc powder.
This may be a slight exaggeration but I preach this to my customers constantly.
I've recycled houses built in the 1880s which contained no rot. They have had adequate roof slope, substantial overhangs and breathable walls with old-fashioned tarpaper under the siding. I've also demolished rotten homes from the 1990s which had short overhangs, not enough roof slope, and vinyl stucco over Tyvek house wrap. Those selling these products preach the value of each one on their own even though it's self-evident that their combined use has
led to billions of dollars worth of property damage.
Overhangs are nothing new and no one can patent them. Therefore you won't see any fancy ads promoting them. But they are the most important part of your house envelope since they keep the water off your walls, unwanted sun from the Windows and provide a great spot to pile crap against your house
.
With inadequate overhangs any little construction error can lead to water infiltration. Large overhangs cover a multitude of sins and allow for a wide variety of wall materials to be used safely.