Concrete Masonry Unit Installation Procedures

How to lay masonry unit walls

During installation, it’s important to consider drawing masonry blocks from a minimum of 1 pallet. Concerning the exterior mortar, it needs to absolutely include a water repellent additive that matches the color of the units. The additive needs to then be added in the right amount to each batch depending on the type of mortar being made (N, S or M) according to the instructions given by the manufacturer.

For cold and hot weather construction practices, you can refer to the National Concrete Masonry Association TEK notes.

Concrete Masonry Unit Installation ProIn order to properly lay the masonry units, you should refer to the best concrete masonry practices. As defined by the American Society for Testing and Materials C90, all defective units need to be rejected and only good quality units should be installed. Each block needs to be laid with the face true, plumb, and level to the line strung horizontally at the ground face. Units need to have uniform three eights inch wide joints vertically and also horizontally on the wall’s finished side. When they get finger-hard, the joints should be tooled neatly in order to make them uniform and straight.

To ensure bond and consistency are properly maintained, you should size and then carefully place the cut pieces accordingly.


In order for any masonry work to be done correctly, proper lighting is essential to avoid errors. All lights should be carefully placed at a certain gap from the wall. Trough lighting is not recommended to be used.


Using motor driven masonry saws, you should make all unit cuts which also includes the ones for boxes, holes, bonding and so forth. The recommended blade for this operation should be either a diamond or an abrasive blade. Make sure to always locate for a great appearance and cut neatly.

Mortar Jointing and Bedding

  1. Units need to be carefully laid with complete mortar coverage on bed joints and heat, but make sure you don’t block cores that need to be filled or grouted with masonry insulation.
  2. When dealing with concave configurations, make sure to tool all mortar joints carefully.
  3. Removing mortar from the masonry units should be done with care and before the mortar has managed to set.
  4. For proper appearance, you should also tuck-point the joints of the scored units, especially the exterior ones since this way you can prevent water damage.

Watch this video showing in detail hot to lay masonry blocks:

Masonry Work and Flashing

Abiding by the best masonry flashing practices, you should consider installing flashing at the points mentioned in the plans.

Weep Vents and Holes

Vents and weep holes should be installed at suitable intervals at any water courses stops over beams, doors and windows and above grade.


All textured faces need to conform to American Society for Testing and Materials C90’s requirements when they’re viewed in normal lighting from 20′ away at a 90 degree angle to the wall.

Article by Echevarria Mendez

I've been working with concrete all my life. It's a material to admire for its strength and beauty.