How to Construct Concrete Block Masonry?
Concrete block masonry is a widely used style for its excellent properties of durability and high resistance to rain, fire, and inclement environmental conditions.
Proper workmanship plays a crucial role in the completion of the masonry structure. Therefore, correct construction procedures must be followed while using concrete blocks masonry.
The standard specifications of the hollow and solid concrete blocks used for the construction of masonry are explained in the article-
Standard Specification of Hollow and Solid Concrete Blocks [PDF]
In this article, we discuss the procedure for constructing a masonry using concrete blocks.
1. Wetting of Concrete Blocks
The concrete blocks need not be wetted before or during laying in the walls. In places with high temperatures, the sides and the top of the blocks shall only be moistened to prevent the absorption of water from the mortar and ensure the formation of the required bond with the mortar.
2. Laying of Concrete Blocks
- The concrete blocks shall be laid in the mortar of the required mix as specified and thoroughly bedded in mortar.
- Mortar shall be spread over the top surface of the previous course, creating a uniform layer with a minimum thickness of 10mm and not exceeding 12mm.
- All the concrete block courses shall be laid truly horizontal, and all vertical joints made truly vertical.
- The concrete blocks shall break joints with those above and below for not less than a quarter of their length.
- Precast half-length closers (and not cut from full-size blocks) shall be used.
- For battered faces, bedding shall be at right angles to the face unless otherwise directed.
- Care must be taken during construction to ensure that the edges of the blocks are not damaged.
4. Provisions for Door and Window Frames in Concrete Block Masonry
A solid concrete block masonry course shall be provided under door and window openings (or a 10 cm thick precast concrete sill block under windows). The course shall extend for at least 20 cm beyond the opening on either side.
In case of jambs of very large doors and windows, either solid concrete blocks or the hollow blocks shall be filled in with concrete of mix 1:3:6 using 12.5 mm nominal size aggregates.
5. Provisions for Roof in Concrete Block Masonry
The concrete course below the roof slab and top of the roof course must be built using solid blocks. The top of the roof course built using solid concrete blocks shall have a smooth finish with a layer of cement sand mortar of 1:3 and 10 mm thickness. It should be covered with a thick coat of whitewash or crude oil to ensure free movement of the slab.
6. Fixtures and Fittings in Concrete Block Masonry
- The fixtures, fittings, etc. in the concrete block masonry shall be built into the masonry in cement and coarse sand mortar 1:3 while laying the blocks.
- The holdfasts shall be driven into the joints of the block masonry during laying.
- Holes, sleeves, chases, openings, etc. of the required size and shape or fixing pipes, service lines, a separate passageway for water shall be formed in the masonry with special concrete blocks while laying.
- After service lines, pipes, etc. are fixed, the voids left shall be filled up with cement concrete 1:3:6 and neatly finished.
7. Finishes in Concrete Block Masonry
- Rendering for the concrete block wall shall not be done if the walls are wet.
- Joints for plastering or pointing as specified shall be raked to a depth of 12 mm.
- Joints on internal faces, unless otherwise indicated, shall be raked for plastering.
- If the internal faces of masonry are not to be plastered, the joints shall be finished flush as the work proceeds, or pointed flush where indicated.
FAQs on Concrete Block Masonry
Mortar shall be spread over the top surface of the previous course forming a minimum uniform layer of 10 mm and not exceeding 12 mm in thickness.
The concrete blocks need not be wetted before or during laying in the walls. In places with high temperatures, the sides and the top of the blocks shall only be moistened to prevent the absorption of water from the mortar and ensure development of the required bond with the mortar.