Question

• Assume that the proposed house is located in Scarborough and within a 100m distance from the coast. Note that the site classification is Class A’

Which of the joint types you recommend for this project and defend your choice. Refer to the project specification to know the masonry construction types recommended for this project

Answer 1

For a structure to remain serviceable, it must be durable throughout its life, assuming a reasonable level of building maintenance is carried out. Crystalline salts in the masonry can be absorbed from either the ground or from materials such as the sand used in the mortar mix. A structure to have the necessary durability to withstand the expected wear and deterioration throughout the intended life – typically 50 years, without the need for excessive maintenance. For any building element, the required durability depends on the exposure environment, the location within the building, and the importance of the structure.

Exposure Environments - Severe marine - Up to 100 meters from a non-surf coast and up to 1 km from a surf coast. The coast is defined as the mean high-water mark.

Masonry units - When masonry units absorb moisture containing dissolved salts, damage can result when this moisture dries out. This damage can affect either the mortar joints (if the mortar is soft) or to the units, and sometimes to both. The mechanism operating is that the dissolved salts crystallize just below the surface as the moisture evaporates and the growth of the crystals causes physical stresses leading to particles being dislodged from the surface; this is referred to as salt attack.

Exposure Grade Bricks are suitable for saline environments and should always be used below the dampproof course and in other locations of severe exposure.

even if a wall is designed to satisfy all the prescribed loads, it should not be so slender as to fail under some unintended or accidental load and it should have adequate stiffness. If the wall is capable of withstanding a minimum level of lateral load of 0.5 kPa, it is deemed to have the necessary robustness.

Elements in the severe marine environment -

1. Masonry units - minimum salt attack resistant grade,

  the characteristic unconfined compressive strength of masonry units in megapascals = 7.5 MPa

English bond is much stronger than a flemish bond for the walls thicker more than 1½ brick. Flemish bond shows a more attractive and pleasing appearance of masonry work.

2. Mortar - M4 grade - [ cement : building lime : sand = 1 : 0.5 : 4.5 ] {suitable for fired clay bricks , concrete blocks}

3. Minimum cover to grouted cavities - 30mm.