Sunday, November 18, 2012

Alhambra Granada Ad Quadratum Ground Plan Part 2

Geometry has been passed down through the centuries.So, my best guest is the Islamic Moors used regulating lines of geometry to develop the roof plan and the hip rafter head cuts for the roof at Alhambra, Granada Spain over the Hall of  Abencerrajes. The Islamic Moors most likely used a Hexadecagon King Post, Ad Quadratum King Post 4 - Squares Rotated in Circle. 16 sided polygon king post for the 8 hip rafters and 8 valley rafters.

Using mitered- beveled  hip rafter and valley rafter head cut, would have never work structurally.

Using an purlin structural ring might have worked, but the purlin would have to an V in the middle of the purlin to follow the roof planes of the valley rafters. 

Plan view for developing the square butt head cuts of the hip rafters without a king post.

Roof surface development for the Ad Quadratum ground plan with the hip rafters developed from a 4 sided polygon and the valley rafters developed from am 8 sided polygon. The jack rafter side cut angles are developed on the real roof surface. As well as the roof sheathing angles. I wonder if they called the roof sheathing angles hopper cuts, like the English carpenters did/do? Did they use roof sheathing angles developed from geometry to cut their roof sheathing material? Or did they scribe and cut the roof sheathing material? 

The Alhambra Granada Ad Quadratum Ground Plan is now a calculator in Rafter Tools.

Rafter Tools help file link for the Alhambra Granada Ad Quadratum Ground Plan Roof Rafters.


  1. I could not get the exact point of your post. can you explain the point of your postings?
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    1. The roof over the Hall of Abencerrajes at Alhambra, Granada Spain is based on Ad Quadratum. In this post I was explaining the different types of head cuts at the peak of the roof. A Hexadecagon King Post,is one option and I was showing how my Rafter tools app now supports the geometry - trigonometry of the roof over the Hall of Abencerrajes at Alhambra, Granada Spain that is based on Ad Quadratum.

    2. Thanks for this reply. i can know easily understand your postings and i must appreciate your work. i am looking forward this kind of work from you .

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