How to do Brickwork in Circular and Flat Arches? [PDF]

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An arch is a curved structure that bridges an elevated or open space that supports heavy load and forces that act from above it. The construction of arches requires fine work and, therefore, skilled workmanship.

This article shall explain the specification of bricks, centering and shuttering, and construction of circular and flat arches.

Specification of Bricks for Arches

1. The arch work shall include masonry for both gauged as well as plain arches.
2. In gauged arches, cut or molded bricks shall be used, and in plain arches, uncut bricks shall be used.
3. The brick that forms the skew of an arch shall be dressed or cut so as give proper radials to the end voussoirs.
4. The defects in the dressing of bricks shall not be permitted either by further use of mortar or the use of chips and bats.
5. In the spandrel wall, the bricks at their junction with the extrude of the arch shall be cut to fit the curvature of the arch.
6. The bricks used for the construction of arches shall be soaked in water before use for a period so that the water shall penetrate the whole depth of the bricks. 

Centering and Shuttering for Arches

1. The centering and shuttering for the arch shall be strong enough to bear the dead load of the arch and the live loads that are likely to come upon it during construction, without any appreciable deflections.
2. The shuttering shall be tightened with hardwood wedged or sandboxes so that the same could be eased without jerks being transmitted to the arch.
3. The sequence of easing the shuttering shall be approved by the engineer.
4. The shuttering shall be struck within 48 hours after the spandrel has been filled in and the arch loaded.

Construction of Circular Arches

1. The circular arches shall be either plain arches and shall be built in half brick concentric rings with break joints, or gauged arches built with bricks cut or molded to the proper shape.
2. The arch work shall be carried up from both ends extraneously and keyed in the center. 
3. The bricks shall be flush with mortar and well pressed into their positions so as to squeeze out a part of their mortar and leave the joints thin and compact. 
4. All joints shall be full of mortar, and the thickness of joints shall be full of mortar, and the thickness of joints shall not be less than 5 mm and more than 15 mm.
5. After the arch is completed, the haunches shall be loaded by filling up the spandrels to the crown level of the arch.
6. Care shall be taken to load the haunches on two sides of the spandrels.
7. When the arch face is to be pointed (and not plastered), the face bricks shall be cut to proper shape or molded so as to have the joints not more than 5 mm thick.
8. These shall be laid with radial joints to the full depth of the arch.
9. The voussoirs shall break joints to the full depth of the arch.

Construction of Flat Arches

1. The flat arches shall be gauged arches of brick cut or molded to the proper shape.
2. The extrudes shall be kept horizontal, and the intrudes shall be given slight camber of 1 in 100 of the span. 
3. The center of the arch from which joints shall radiate shall be determined by the point of the intersection of the two lines drawn from the ends of the arch at the springing level and at 60 to horizontal.
4. In flat arches, bricks shall be laid with radial joints to the full depth of arch and voussoirs breaking joints with each other.
5. The arch work shall be carried up from both ends simultaneously and keyed in the center.
6. The thickness of the mortar joints shall not exceed 5 mm.
7. Flat arches may be used for the sake of appearance, but to carry loads of the wall above, and these shall be used in conjunction with relieving arches, lintels placed below.

FAQs on Construction of Arches

Read More:
1. Types of Arches Construction based on Shape, Material, Workmanship
2. Types of Openings in Walls, its Parts and Types of Lintels and Arches for Openings
3. What are Indeterminate Arches in Construction?