1. 
   Diaphragm arch
   A diaphragm arch is a transverse wall-bearing arch forming a partial wall dividing a vault or a ceiling into compartments. When used under a wooden roof, it has the advantage of providing a partial firebreak. It was first used in Roman Syria, during the 2nd century AD. ...
   Found op http://en.wikipedia.org/wiki/Diaphragm_arch
   
   

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