General Contractor Practice Exam

What is required for masonry walls to properly bond with plaster?

1. Coating with paint

2. Leaving the wall dry

3. Moistening the wall

4. Applying a chemical sealant

The correct answer is: Moistening the wall

For masonry walls to bond effectively with plaster, it is essential to moisten the wall before application. This moisture helps to prepare the surface, ensuring that the plasters adhere properly and sufficiently. Masonry surfaces, especially if they are dry and porous, can absorb too much water from the plaster mix, which can hinder the curing process and weaken the bond. By moistening the wall, you create a balanced environment, reducing the absorption of water from the plaster and thus allowing for a stronger bond. This practice is common in masonry work, as it enhances adhesion and helps prevent cracks and other issues that can arise from improper bonding. Other options do not support the required conditions for bonding plaster to masonry. For example, coating the wall with paint can create a barrier that obstructs the plaster from forming a proper bond, while leaving the wall dry poses a similar risk of inadequate adhesion due to excessive moisture absorption. Applying a chemical sealant may also interfere with the plaster's ability to adhere, as it can form a slick surface that isn't conducive to bonding. Hence, moistening the wall is the best practice to ensure effective bonding of plaster to masonry.