Roofs 101

The roof on your house performs a few different tasks, the main one being to shed rainwater effectively (at least in New Zealand, where it can rain a lot). Given a simple rectangular floor plan, there are two basic roof forms, the hip and the gable, both of which are present at our place:

Hipped roof on our house

Gable on the end of our garage

Other less common roof forms are the gablet, the gambrel, the Dutch gable and the mansard amongst others.  Unfortunately, there are so many different opinions about the definition of each of these that it is difficult do decipher what is 'correct' and what is just common usage (abusage?).

The New Zealand Period House (Arden & Bowman, Random House, 2004) describes a gambrel roof the way a gablet roof is defined in the UK and elsewhere.  I prefer the more descriptive 'hip and gable' which is used in Asia to denote a temple style roof, although the term Dutch gable is often used here, despite it looking nothing like the gable on a Dutch house.

Gablet or is that Gambrel? Or Dutch Gable? Photo: Bill Bradley

A gambrel roof in the US (think hay barn) would be described as a mansard roof in NZ, and possibly the UK, although mansard applies more correctly to a hipped or four sided version, not the one below:

Gambrel or is it Mansard? Photo: Steel Frame Concepts

Back to my copy of The New Zealand Period House, they describe a Dutch gable roof the way a half hip or Dutch hip is described elsewhere:

Half Hip or is it Dutch Hip? Or Dutch Gable? From Houseplans24.com

So you can see that there are very clearly defined definitions for the various basic roof styles.

Well, I'm glad I cleared that one up!  And this is just a roof on a rectangular box.  Introduce a non-rectangular floor plan with bays, lean-to's, valleys, clerestoreys etc, perhaps a flat or skillion roof, then we can look at framed roofs versus the trussed variety, purlins, battens, chords and webs, rafters, stringers, barges, soffits....