A Vault in the Making

One of the simplest forms of a vault – The Barrel Vault had been traditionally used in buildings since date. In regions with adverse climatic conditions, a traditional system of providing a shade to a building is always recommended. The process though cost effective in terms of materials, is highly time consuming and labour intensive. Hence with modern times, traditional systems of construction dissipated. With the preference towards modern methods of construction and rampant use of concrete, a traditional brick or stone vault is rarely constructed. The construction method includes a simple barrel vault modified with a concrete grade slab for strength and durability. Two projects – Matter Campus, Goa and Moira House, Goa have been taken as a reference for vaults of different spans and details.

01. A section through our project ‘Matter Campus’ in Salvador Do Mundo, Goa. The vault roof of the building is seen in juxtaposition with an adjoining chapel next door.

02. A section through the Matter Campus building showing the details of the Vault. The bricks are laid on top of a curved plywood shuttering, followed by a layer of concrete, followed by brick-bat-coba as a form of a traditional waterproofing topped with a china mosaic finish.

03-04. A section through our project ‘Moira House’ in Moira, Goa. The vault roof extends to the entire length of the building. The bricks are laid on top of a curved MS shuttering, followed by a layer of concrete, followed by brick-bat-coba as a form of a traditional waterproofing topped with a cement plaster finish.

05-10.

Firstly during the construction of the slab, 8mm thick reinforced rods are placed on the beams on two sides at an interval of 150mm, each having a length of about 1500mm. These dowels can be of varying thickness, length and interval depending on the size of the vault. A structural engineer’s consultation is necessary at all stages.
MS shuttering with MS sheet on top in the shape of a half barrel is used in this vault. The radius of the curve varies. For a span of 5000mm, a radius as 1800mm has been considered in consultation with our structural engineer. The shuttering is made in sections and only a part of the vault is done at a time. The width of the shuttering can vary with the length of the vault. The width considered here is 1500m. For speeding up the work, the width can be increased or multiple shutters can be made. Scaffoldings for the labourers to climb and work to be provided as necessary.
Bricks of size 230 x 115 x 75 mm are manually laid on top of the shuttering with the 75mm side facing the shuttering. A plastic cover has been installed on top as the construction took place during monsoon season.
MS shuttering with plywood sheet in the shape of a half barrel can also be used. The radius of the curve can vary. For a span of 4000mm, the radius of the curve was taken as 1500mm in consultation with the structural engineer.
After the brick layering, the dowels provided on either beams, are tied as a grade slab with 8mm reinforced bars along the shape of the vault from the top at an interval of 150mm. A 100mm layer of concrete is added to the top of the brick covering the reinforcements.
Once the concrete has set in, within an interval of 2 days, the shuttering can be shifted to the next section and the finished vault section is cured for 21 days.

11-13. Image of the vault after the shuttering is shifted from one part of the vault to the other.
14-15. Image of the vault from the above showing the brick and grade slab layers.

16-17a,b,c.

For the waterproofing, laterite blocks are broken into smaller pieces. The process is laborious and can start simultaneously with the vault construction.
A,B,C – Traditional waterproofing is done on top of the slab using the small pieces. The thickness can be 50mm sloping down to 25mm. Small aggregates can be used on the lower side of the slope. Once the waterproofing is completed, a layer of concrete is poured to cover the small laterite pieces and aggregates.

18-20. Image of the vault after once the shuttering and scaffoldings are removed. A layer of powdered brick mixed with red cement is applied on the cracks if there are any and if the brick edges are not clean.

Tiles have been used as the final finish layer after the traditional water proofing in the Matter Campus project. Cement plaster has been used in the Moira House project as the final finish layer.

22-25. Black matte tiles were broken into smaller pieces and placed carefully above the waterproofing layer making sure all gaps are filled. Construction workers adding the tile layer to the vault. The process involves breaking the tiles into smaller pieces and fitting them like a jigsaw puzzle. The smaller gaps are then packed with cement. Construction workers cleaning and dry polishing the China Mosaic layer and the finished China Mosaic waterproofing layer in Matter Campus.