M: used for below-grade (at or below ground-level) load-bearing work, as well as for chimneys and brick manholes S: used for below-grade work including foundation walls, brick manholes, retaining walls, sewers, walkways, patios, and pavement N: a general-purpose mortar mix that can be used for both interior and exterior above-grade (above ground-level) work O: also referred to as “pointing” mortar, used for above-grade, non-load-bearing, and decorative work
Pre-wetting your containers and tools also makes clean-up a little easier. While you’ll still have some mortar stick, it won’t be as bad if you pre-wet everything.
Always gear up before you even open a bag of mortar mix. Just the act of opening the bag can cause dust to escape.
Pouring a puddle of water in the bottom of the container before you add the dry ingredients also helps decrease clouding.
Mix well so that the mortar has a consistent texture. You don’t want dry spots or puddles of water anywhere. You can also think of the proper consistency as being something like thick peanut butter. The amount of water used can vary drastically depending upon the weather, how wet the sand is, and the variety of mix you’re using, so add it slowly. [7] X Expert Source Ryaan TuttleHome Improvement Specialist Expert Interview. 17 February 2022.
Your mortar will set more quickly if it’s hot outside. Compensate for this by making smaller batches so you won’t waste as much. [9] X Research source
M: 3 parts Portland cement, 1 part lime, 12 parts sand S: 2 parts Portland cement, 1 part lime, 9 parts sand N: 1 part Portland cement, 1 part lime, 6 parts sand O: 1 part Portland cement, 2 parts lime, 9 parts sand
When you pour or stir the dry ingredients, dust inevitably rises up. It’s easy to inhale if you’re not wearing a mask.
If you’re using a mechanical mixer, pour about half of the water you plan to use into the mixer first. Then, add half the sand and any lime, followed by the concrete and the rest of the sand.
Pour slowly so the ingredients won’t cloud up as much. This is not only a hazard but causes you to lose part of your batch. If there’s wind, turn so the wind is blowing away from you as you pour. You don’t want the dust blowing directly onto you, even when you’re wearing safety gear.
The amount of water you’ll need can vary greatly depending on humidity, air temperature, and other factors. Just add it slowly and pay attention to the consistency of the mortar as you go.
The outside temperature affects how quickly your mortar will set. If it’s hot, your mortar will set much faster. Make smaller batches if you’re working in higher temperatures. [17] X Research source
You can also add pigment after you’ve mixed your mortar. This gives you a little more control over the specific shade, especially if you’re using something you’ve never used before. However, it can be more difficult to keep it consistent from batch to batch. Add the exact same amount of pigment using the same process for all subsequent batches so all of your mortar is the same color throughout the project.
Accelerators increase the mortar’s workability in cold temperatures. Use hot water to mix mortar with an accelerator added. In hot weather, you can add a retarder to slow the rate of hydration and keep the mortar workable for a longer period of time. Use cool water to mix mortar with a retarder added. Some masons will even add ice to the water to lower the temperature further. It’s still best to mix smaller batches in hot weather because mortar can “flash set” and become unusable quickly—even with a retarder.
If you’re making your mortar from scratch, you can buy air-entrained Portland cement to use. Some pre-made mixes also use air-entrained Portland cement—just read the bag.
The ingredients used in these admixtures are protected as trade secrets, so there aren’t general instructions for how to use these products. If you’re mixing one of these products into your mortar, follow the manufacturer’s instructions precisely.
Since efflorescence is caused by evaporating water, water repellant admixtures help with that too.
Many pre-made mixes have various additives already in them. Check the ingredients in your mix carefully to make sure you don’t add something separately that’s already in the mix—that could weaken your mortar or make it unusable. With pre-made mixes, you still have to follow the same masonry practices that you would if you were mixing in an additive yourself. These requirements will be listed on the bag, so read them and follow them carefully.
