Building construction Prepared by : Rall no : : Nayani Paril : Patel Nikunj : Parmar Mihir : Patel Adarsh : Patel Bhavin Guided by : Proff. Mital Dholawala

HOLLOW CONCRETE BLOCKS AND CONSTRUCTION

CEMENT CONCRETE MASONRY Cement concrete is widely used for the construction purpose due to its various advantages over the other building materials. Hollow concrete units are manufactured from light weight aggregates. They may be used for load bearing as well as non load bearing walls. The concrete blocks are moulded in machine in the various standard sizes, as follows, (1) Standard sizes hollow concrete blocks : 39cm*19cm*30cm (2) Hollow building tiles : 39cm*19cm*20cm (3) Hollow concrete blocks for partition : 39cm*19cm*10cm To ensure maximum economy in construction, the overall length and height of walls is so fixed that the maximum use of full and half length blocks is possible.

MANUFACTURING OF CONCRETE BLOCKS The ratio of cement of aggregate should not be more than 1:6. The blocks should be taken out from the moulds only when the concrete has set sufficiently. In order to obtain better finishing, the machine casting is more preferred than hand casting. The blocks should be used only after 3 to 4 weeks of taking out from tank. The compressive strength of blocks should not be less than 30 kg/cm*cm. after 28 days curing.

WALL CONSTRUCTION WITH CONCRETE BLOCKS The various point should be followed during the construction work : The concrete blocks used in masonry are dry. Blocks of successive courses should be laid in such a way that the vertical joints are staggered. The joints should be uniform and 5 to 10 mm thick. Generally cement-lime-sand mortar of mix proportion is used and it should not stronger than the concrete mix used for concrete blocks. The blocks used for external walls should have absorption less than 10%. For internal walls the absorption should be less than 15%.

Hollow concrete blocks

ADVANTAGES OF HOLLOW CONCRETE BLOCK MASONRY The concrete blocks are available in regular and uniform size and less weight, the masonry construction done very rapidly. As the blocks are light in weight they easy to handle construction is speedy resulting in less labour cost. It is possible to construct thin wall with concrete blocks resulting in the increase of floor area. As the blocks are hollow, there is saving of material. As the size of blocks is large, the number of joints are less and hence there is saving of mortar. The rough surface of concrete blocks makes plastering easier.

CAVITY WALLS

Introduction : A cavity wall consists of two separate walls or leaves with cavity or gap of 5 to 8 cm. between them. The outer wall known as outer leaf, consist of 10 cm. thick and the inner wall is more thick and strong to carry the impact load safely. The two walls or leafs are tied together with metallic cotta ties to obtain structural stability. They are spaced at 90cm. Apart horizontally and 30 cm to 45 cm. apart vertically staggered position.

Advantages of cavity walls : The moisture can not enter from the outer leaf to the inner leaf, as there is no direct contact between two leaves except at the wall ties. The cavity walls provide good insulation against sound. The problem of efflorescence is very much reduced. The construction of cavity wall is economical. As the walls are having cavity inside the loads on the foundation are reduced.

Masonry cavity walls Products Earth wool Dritherm Cavity Slabs are a range of lightweight semi rigid or rigid slabs of glass mineral wool with a water repellent additive. They are manufactured to fit between wall ties at standard vertical spacings.

Typical construction : Brick or block outer leaf (which may be rendered), brick or block inner leaf with cavity fully filled with Earthwool DriTherm Cavity Slabs. Internal finish of 12.5mm standard plasterboard on dabs. For buildings from 12m to 25m high, British Board of Agrèment (BBA) Certificate No 95/3212 imposes additional requirements. For additional information see the BBA Certificate or contact our Technical Advice and Support Centre on

Installation : Earthwool DriTherm Cavity Slabs should be kept clean and free from mortar droppings. All joints should be closely butted. Any cutting and fitting should be neatly done and not distort the layers of glass mineral wool which comprise the product. Damp proof courses should be installed to ensure that penetrating water is directed only to the outer leaf. See pages for detailed installation instructions.

Performance : Thermal performance Earthwool DriTherm Cavity Slab 37 Standard has a thermal conductivity of either W/mK or W/mK depending on thickness. Earthwool DriTherm Cavity Slab 34 Super has a thermal conductivity of W/mK. Earthwool DriTherm Cavity Slab 32 Ultimate has a thermal conductivity of W/mK. Fire performance Earthwool DriTherm Cavity Slabs are classified as Euroclass A1 to BS EN

Masonry cavity walls and fire performance : Open cavities must be stopped to prevent the passage of fire. This is required at specific intervals and the cavity barrier has to provide at least 30 minutes fire resistance. If the cavity is fully filled and is built in accordance with Diagram 13 (Diagram 34 in Volume 2) of Approved Document B: 2007, Volume 1, ‘Dwellinghouses’ cavity barriers are not required.

BRICK CAVITY WALLS The cavity walls for flat and inclined roofs. In case of brick cavity wall, each leaf is half brick thick. This type of walls are capable of taking load of two storeyed residential buildings. The cavity between two leafs are tide may very from 40 mm to 100mm in width. The inner and outer leafs are tide together with metallic wall ties, spaced at 90 cm. apart horizontally and 30to 45cm apart vertically in staggered position.

BRICK CAVITY WALLS : The cavity should start near the ground level and ends near the eaves level in case of sloping roof or near the coping in case of flat roof with parapet wall. The cavity should start 15 cm. Blow the damp-proof course level ;so that the condensed moisture below the level of dpc can be drained out. The bottom of cavity should be0 atleast 15 cm. above the outside ground level, so that entry of moisture can be prevental.

Brick cavity walls

POSITION OF CAVITY OF FOUNDATION At foundation level the various alternatives are adopted in the provision of cavity. The cavity may either be extended upto the concrete base or up to 15 to 30 cm. below the damp proof course. In case where the ground water level is high and if the brick work below ground level is not constructed carefully; the water will enter through the joints and will collect in the cavity. This water will travel through the inner leaf and will cause dampness in the flooring. Alternatively cavity may be provided upto ground level or upto 150 to 300mm.

Position of cavity of foundation

ROOF AND AT OPENING LEVELS

Roof and at opening levels

THANK YOU