Starting the Arches on the third week

During the third week of the course Design and Build with CEB the masonry with 1 and 1/2 brick was continued until arriving to 140cm. This was the starting point of our arches with 170cm diameter. The centering was made by a local carpenter and is a contemporary reinterpretation of the traditional ones, instead massive wood, oriented strand boards (OSB) were used to shape the arches form. The main rules to place the bricks were to have the radius line that crosses the half face of the brick to be perpendicular to the arch tangent passing in that point, besides this, the brick has to be perpendicular to the centering (that was previously aligned with the wall plane and perfectly vertical). The bricks has to touch each other in the arch intrados , so the mortar has to be placed in a triangular shape. A stone is placed in each joint at the arch extrados to assure the brick position while the mortar is fresh. When arriving to the last 4 to 6 bricks, these can be positioned without mortar to study the keystone. When arriving to the end respecting the brick module, there is no need of a keystone. In this case we can just fill the joints with the bricks placed. When there is the need of a keystone we cut it with the measures of the space left to fill and finally we complete the filling of the joints and introduce the keystone with a bit of pressure. The centering is taken out while the mortar is still fresh. Like this the bricks can still adjust to the perfect forces load. This means that the arch has to be, ideally, started and finished in the same day… or night… one of our keystones was cutted after midnight with the light of spotlights…