Friday, May 16, 2014

I have noticed on a lot of custom homes that there seems to be a flat top on the roof, why is this?

Q:

I have noticed on a lot of custom homes that there seems to be a flat top on the roof, why is this?

A:

You are right that a growing number of custom homes being built today have a flat spot on the very top of the roof, the size and shape of it depends totally on the roof design.

.The reason that it exists is more to do with the rules and regulations of building in most area’s these days then architects wanting it there for aesthetic reasons.

The major trend in roof design is to have grander type roofs, to achieve a grander roof you need to build a larger roof; the only way to build a larger roof is to build it higher. To build a higher roof you simply increase the pitch of the roof (steepness). The problem with increasing the pitch of the roof is that the roof then rises up higher to meet at a peak in the middle of the building. If you have a two story house that has 9 foot ceilings (common for most custom homes today) then your roof would be starting at 18 feet off the first floor.
The top of the first floor is the starting point where municipalities measure the height of a home. Every building department will have different height restrictions for residential dwellings. If the height restrictions are 38 feet in your municipality and your roof is starting at 18 feet then that leaves you with only 20 feet of height to build your roof.

20 feet of height might sound like a lot but when you have a steep pitch on your roof it’s not as much as you think.

A common steep roof on custom homes is what is called a 16/12 pitch; this means that for every 16 inches the roof travels vertically it takes 12 inches of room horizontally. In this scenario if you had a 16/12 pitch and you wanted your home to come to a peak at the 38 foot height limit then the roof would have to be 30 feet wide. With a 30 foot wide roof the walls would be stepped in from the overhangs about 1.5 feet or 18 inches on each side. That means the building below would only be 27 feet wide.

The average custom home these days is at a minimum 3500 sqft spread out over two floors, that is 1750 sqft per floor. You would have to have a house that is about 65 feet long, and then add on another 25 feet for the attached garage. What you end up with is a bowling alley, in-town lots are getting hard to find for a house that wide.

To achieve the same square footage with a custom home that isn’t long and narrow you increase the width of the home from the 27 foot mark. As you increase this number (if the pitch of the roof stays unchanged) the roof gets higher and starts to exceed the height limits.

This is where placing a flat spot on the very top of the roof comes in to play. The flat spot makes it simpler for designers and architects to change the depth of the building without changing the general look and grandness of a steep roof.

Rob Abbott
Operations Manager
Village Builders Inc.  

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