A Pattern Language of Natural Homes No.220 Roof Vaults

 

This is the second of a series of articles about A Pattern Language by Christopher Alexander where we illustrate and discuss the patterns using homes and buildings made from natural materials like stone, clay, wood and straw.

 
   
 

Alexander admits that this pattern is the most contentious of them all. A roof carries with it cultural heritage and social expectations which he tries to avoid by a fundamental analysis of the roof while still meeting the requirements of the related patterns such as No.117, Sheltering Roof.

The criteria he identifies are that the roof: satisfies the psychological sense of safety; provides a lived in space rather than just a hat above the living spaces; give an indication of the social layout of the building; should not be a complicated contrived structure; should avoid bending requiring tensile materials, and should shed rain and snow suitable for its climate.

Taking other patterns in to consideration then collectively these exclude the flat roof, pitched roof and geodesic domes (ironically a popular structure many eco-villages like to play with).

 

 

 
         
 

Alexander notes (from 1977 when his book was published) that, "...we believe these tension materials [wood, steel] will become more and more rare". The scarcity of tensioning materials like wood is exactly why the non-profit organisation La Voute Nubienne helps communities in Africa to build the roof vault solution Alexander proposed 35 years earlier. Their work in sub-Saharan Africa is helping to replace the traditional use of timber for

 

roofing. Population growth in the region, together with increasing desertification and regression of forested areas, means that the traditional use of timber is no longer feasible.

You can see more of their work, as shown above, on their English facebook page Association la Voute Nubienne.

 
       
   

The picture far left is Sky House, one of the beautiful 'relaxed' homes built by the natural builder SunRay Kelly in the USA. The roof is a good example of pattern No.116 Cascade of Roofs and No.117 Sheltering Roof, but a look inside the attic bedroom (left) demonstrates pattern No.220. It shows the convex curve that Alexander prescribes but achieved here with natural roundwood timbers that retain much more strength than milled timbers.

Here's a short film about SunRay's building philosophy which starts with a view of Sky House and the window of this bedroom.

SunRay is one of several natural builders using roundwood timber methods. In the UK Ben Law developed efficient building methods reviving the cruck frame using green roundwood timbers.