How to Mix Brick Mortar
Mixing brick mortar can be an important key to building a brick, block, or stone wall that you want to last. The brick may be made of the highest quality material, but if the mortar doesn't hold up the way in which you need it to, the wall will crumble sooner than you may expect. It's all a matter of knowing how to mix the mortar. Here are five types of mortars, and information on how to mix them, as well as what projects you should use them for.
Tip 1 - Understanding Mortar Components
To properly mix your brick mortar, first you will need to learn that each of its ingredients -- Portland cement, sand, water, and lime -- contributes its own qualities to the finished mortar. The cement provides bonding, while lime strengthens and reduces shrinking and prevents premature drying. Sand helps bonding, and water is needed to create the right viscosity, or thickness.
Tip 2 - Understanding Mortar Types
In mixing mortar you should know which type to use for construction of your wall. This will be a factor not only in the wall's durability but in it's "spreadability." All five mortars described in this article contain the same basic ingredients listed in the paragraph above. All that is different among the five types is the proportions of mortar ingredients.
Tip 3 - Mixing and Using Type "N" Mortar
Use Type "N" mortar for above grade applications. Mix 1 part cement, 1 part lime, and 6 parts sand. Use this mortar if you need a mortar of medium strength and for either indoor or outdoor applications. In general avoid using it in walls that are load bearing. Also use it for indoor projects and most home improvement projects.
Tip 4 - Mixing and Using Type "M" Mortar
Mix this type at a ratio of 3/1/12: 3 parts cement, 1 part lime, and 12 parts sand. Use this type for load bearing walls, retaining walls, foundations, or for other below grade applications where the mortar will come into contact with soil. If you want a higher strength mortar, this is the type you should use.
Tip 5 - Mixing and Using Type "S" Mortar
For Type "S" mortar use a ratio of 1 part cement, 1/2 part lime, 2.25 parts sand. Like type M mortar, use Type "S" for below grade applications where greater strength is required, and lighter weight projects such as home improvement projects requiring greater mortar strength.
Tip 6 - Mixing and Using Type "O" Mortar
For Type "O" ("pointing") mortar where you have lighter weight, above grade, and non-load bearing projects, mix 1 part cement, 2 parts lime and 9 parts sand. This mix will give you 350 psi compressive strength. Use it for both interior and exterior applications.
Tip 7 - Mixing and Using Type "K" Mortar
Do not plan on using Type "K" Mortar. It is not one you will normally have application for, is used mostly where strength or load bearing is not a factor. A typical application would be extending the life of old or ancient bricks. Mix ration for "K" type mortar is 1 part cement, 3 parts lime and 10 parts sand.