Mortar types explained: Type N vs Type S, and how much you need

The two common types

The letters form a sequence — M, S, N, O — from most to least cement-rich (a mnemonic is the alternate letters of “MaSoN wOrK”). Type M is the strongest and least workable; Type O is a low-strength mortar for interior or repointing work. Stronger isn’t always better: a mortar much stronger than the brick or block around it can crack the units instead of itself, which is why repointing old, soft brick uses a weaker, lime-rich mix.

How much mortar you need

Both Quikrete products give the same coverage: an 80 lb bag lays up to 13 standard 8×8×16 blocks or 37 standard bricks. That is the best case with neat ⅜ in joints; the Brick Industry Association recommends adding 15–25% to mortar quantities for waste. Worked through on how many bags of mortar per 100 block and how many bags of mortar per 1000 brick.

For stone veneer, Quikrete sells a separate Veneer Stone Mortar, which covers about 17 sq ft per 80 lb bag as a ½ in scratch coat — see how much mortar for stone veneer.

Premix, masonry cement or portland and lime?

• Premixed mortar mix (cement, lime and sand in the bag) — add water and go. Easiest for small jobs, and the proportions are consistent.
• Masonry cement — a pre-blended cement and lime, mixed on site with sand. BIA’s rule of thumb is about eight bags of masonry cement per 1,000 modular bricks.
• Portland cement, hydrated lime and sand — the traditional site mix, using the proportions in the table. The same cement makes concrete at 1:2:3 with sand and gravel; see what is the concrete mix ratio.

Mixing and working mortar

• Add water gradually and mix until the mortar holds its shape on the trowel but spreads easily — stiffer for block, a little softer for brick.
• Mix only what you can use before it stiffens. Mortar that has begun to set shouldn’t be brought back with more water.
• In hot, dry weather, dampen very absorbent brick or block so it doesn’t pull water out of the mortar too fast.
• Tool the joints when they are thumbprint-hard. A concave joint sheds water best.
• Don’t lay mortar in freezing weather. Quikrete says to protect cement-based mortar from freezing for at least 24 hours.

Colour and consistency

Mortar colour affects the look of a wall almost as much as the brick does, and it varies with the sand, the cement and especially the water. On a visible wall, use the same product and the same water for every batch, measure the water rather than guessing, and mix full bags so the proportions stay constant. Test coloured mortar on a small sample panel first, because it dries lighter than it looks wet. Keep a few spare bags from the same lot for repairs, since a later batch may not match.

Mortar isn’t concrete — or stucco

Mortar is made to bond units together in thin joints; it has no gravel and is too weak and sticky for slabs or footings. Stucco is a related cement-lime-sand plaster for walls, with its own proportions and products — see how many square feet does a bag of stucco cover. And everything here is caustic when wet: wear waterproof gloves and eye protection.