You’re ready to start on your masonry project. You’re ready to tackle that wall, patio, or fancy barbecue you’ve planned on, and you have decided on the material you want to use; be it brick, stone, or concrete block. But, before you do, it’s time for a little mortar education, as you want to use the best bonding material possible to keep your project well intact.
Mortar is a cement mixture used to bond bricks and stones etc. together. Mortar is comprised of cement, lime, and sand, and by adding water. Mortar is classified into four main types, each type having different amounts of the added sand and lime. Different mortar types are used depending on the purpose of the structure being built. Some structures need more holding power than others due to pressure and load factors. Flexibility of the mortar is also a factor in the bonding process due to expansion and contraction related to temperature and weather changes, soil conditions, and acts of nature.
Mortar can be mixed three ways: from scratch using separate bags of Portland cement, hydrated lime, and sand; from masonry cement (Portland cement premixed with lime) and sand; and from bags containing all three ingredients in the proper proportions for the strength and type needed. The last type is generally the easiest type to use in home improvement projects. Premixed mortar comes in types M, N, S, and O.
Type M is the strongest type of mortar. It has the highest compression strength. Type M is used for walls bearing heavy loads, such as retaining walls and foundations, and is also used with stone as the strength of the mortar mimics that of the stone being used. Type M mortar is used mostly for commercial construction projects and home building. Type M is is comprised of 1 part cement, 1/4 part lime, and 3 3/4 parts sand.
Type S is a strong mortar used by home owners which has medium-high compression strength, and tensile strength, giving it more flexibility. It is good for walls, retaining walls, foundations and patios where soil pressure, as well as earthquakes are an issue. Type S contains 1 part cement, 1/2 part lime and 4 1/2 parts sand. It’s strength is about 75% of type M.
Type N is a medium strength mortar. Type N is most often used by home owners. It is a good choice for projects with bricks and blocks that are not load bearing, as well as for garden walls, chimneys, and barbecues. Type N has 1 part cement, 1 part lime, and 6 parts sand. It has about 33% the strength of type M mortar.
Type O mortar is used for interior work only, for non-load bearing use. It has a low compressive strength and is used on indoor projects where weather, soil, and pressure are not a factor. Type O is made up of 1 part cement, 2 parts lime, and 9 parts sand, giving it about 14% the strength of type M.
There you have it for some mortar education. Remember to follow the directions on the bag of mortar so you know how much water to use. Mortar should be mixed in a wheelbarrow or mortar pan in batches up to 1 cubic foot (about 7 1/2 gallons). That’s about as much as one person can handle in the time it takes for the mortar to begin to harden (about 1 1/2 hours).
Most cement you see is called Portland cement. Remember, cement itself is only the dry powder substance used to create mortar, concrete and stucco. Portland cement is not named after Portland, Oregon. Portland cement was developed from natural cements made in Great Britain in the early part of the nineteenth century, and its name comes from its similarity to Portland stone, a type of stone that was quarried on the Isle of Portland in Dorset, England.
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