Mortar is graded by letter, and the letters are not a quality ranking — they are a strength and flexibility trade-off. Pick the wrong one and you either get a wall that cracks at the joints or, worse, a mortar harder than the units it bonds, which pushes the cracking into the brick itself. In Los Angeles, seismic design pushes most structural masonry toward Type S. Here is how the grades divide up and what to buy for the job in front of you.
The short answer for LA work
Type S is the default for structural masonry in Southern California: block walls, foundation and below-grade work, brick and stone veneer, and anything an engineer has drawn. Type N is the softer, more forgiving grade for above-grade, non-load-bearing work — interior partitions, chimney crowns above the smoke chamber, and repointing older soft brick. Type M is the highest-strength grade, reserved for heavy below-grade loads and hard stone; it is specified rarely on residential work and is generally over-specified when it shows up on a house.
The counterintuitive part is that stronger is not better. Mortar is designed to be the sacrificial element in a wall — it should crack before the masonry unit does, because a cracked joint is repointable and a cracked block is not. Matching mortar strength to unit strength is the whole discipline.
| Type |
Strength |
Best For |
Avoid On |
| Type S |
1,800 psi |
Block, veneer, below grade |
Soft historic brick |
| Type N |
750 psi |
Above-grade, non-structural |
Retaining and foundation walls |
| Type M |
Highest |
Heavy loads, hard stone |
Most residential work |
Type S: the Los Angeles standard
Type S delivers roughly 1,800 psi with good bond and lateral strength, which is why it dominates in seismic country. Anywhere a wall has to resist soil pressure or lateral load — a block retaining wall, a garden wall, a foundation, a veneer that has to stay attached during a shake — Type S is the specification.
You can buy it two ways. Pre-blended dry mortar is the contractor's choice for consistency: our 94 lb. pre-blended Type S mortar is factory-blended for uniform batches, gives a 2-hour working time, and meets ASTM C-270 and UBC 21-15. The 60 lb. bag is the same mix in a size a single mason can move all day. For a full-strength mix with the masonry sand already graded in, Mason Mix Type S is a commercial-grade product suitable above or below grade and for tuck-pointing damaged joints; it exceeds ASTM C 270 and a pallet is 42 bags.
Block work is where most of this goes. Our guide to concrete blocks in LA covers pallet counts and delivery planning, and the rebar and accessories guide covers the reinforcing that turns a stacked wall into a structural one. Mortar bonds the units; the steel and grout carry the load.
Type N: softer, and right more often than people think
Type N is about 750 psi and is specified for above-grade, non-load-bearing masonry. Our 60 lb. Type N mortar mix is a blend of fine sand and Type N masonry cement for laying brick, block, or stone, and it meets ASTM C 270 for the grade. A pallet is 56 bags.
The case for Type N is repointing. Los Angeles has a large stock of pre-war brick — bungalows, courtyard buildings, storefronts along the older commercial corridors — laid with soft lime-rich mortar and relatively soft brick. Repointing that wall with a hard Type S mortar traps moisture and moves the stress into the brick faces, which then spall. Type N is the closer match, and on genuinely historic buildings a lime mortar softer still is the correct call.
Deck mud is a different animal
Not every bag with "mortar" on it is wall mortar. Our Type N deck mud is a floor product: it floats over metal lath, prepared concrete, or an approved waterproof membrane to level floors and countertops before tile, conforms to ASTM C 144, and is explicitly not for vertical or overhead use. If you are setting tile rather than laying units, our guide to tile setting materials covers thinset, grout and the rest of that system.
Type M: high strength, narrow use
Type M is the strongest of the standard grades and belongs where masonry carries heavy compressive load or sits in continuous contact with earth — deep retaining structures, some hard stone masonry, and specific commercial details. It is rarely the right answer on a house, and using it as a general-purpose "extra strong" mortar is the classic way to damage a wall.
We stock Type S and Type N across the Mortars & Aggregates collection. If your plans call out Type M, send us the spec and quantity and we will source it for the job.
Mixing your own from Portland and lime
Field-batching still has a place, particularly when you need a custom color or a lime-rich mix for historic repointing. Our 47 lb. Type I/II Portland cement meets ASTM C150 and combines with sand to make mortar, stucco, or concrete with a 60-minute working time. The 94 lb. Type II/V low-alkali Portland is the grout and general-construction grade.
Two warnings. Proportioning by shovel rather than by measured batch is how a wall ends up with joints of three different strengths and colors, and colour variation is permanent. And a site-mixed mortar is only as good as its sand — washed, properly graded masonry sand, not whatever is in the pile.
Mixing, working and curing in LA weather
Add water to the powder, not the reverse, and mix to a consistency that holds a ridge on the trowel without sagging. Let it slake for a few minutes, then remix. Pre-blended Type S gives you about two hours of working time and Type N similar; retemper with a small amount of water once if it stiffens, never twice, and never after the initial set has started.
Heat is the local problem. On a summer afternoon in the Valley or the Inland Empire edge of the basin, both the mortar and the units will pull water out of the joint faster than the cement can hydrate, which produces a chalky, weak bond. Damp the units, shade the mud board, work smaller batches, and mist finished walls for the first day or two. In coastal fog, the opposite applies — joints stay green longer, so give them time before tooling.
Tool the joints when the mortar is thumbprint-hard. Too early and you smear the face; too late and you burnish rather than compact the joint, which is the difference between a joint that sheds rain and one that lets it in. A concave joint is the standard for weather resistance in almost all LA exterior work.
Estimating and buying
Coverage varies by unit size and joint thickness, but the practical planning number is bags per block or per hundred brick — ask us and we will run it against your unit count. Buy a little long: a partial pallet returned is cheaper than a colour-mismatched second batch two days later. Pallet quantities are on the product pages — 42 bags for Mason Mix Type S, 56 for the 60 lb. Type N.
Store bags off the ground and covered. Mortar cement is hygroscopic and a bag that has taken on moisture will lump and lose strength even if it looks fine. Browse the Masonry category for units, reinforcing and accessories, and we deliver mortar by the pallet across Los Angeles County.
Frequently asked questions
Can I use Type S everywhere to keep it simple?
For new block and veneer work in LA, largely yes — it is the specified grade for most of it. The exception that matters is repointing older soft brick, where Type S is harder than the brick and will cause spalling. Match the existing mortar there instead.
What is the difference between mortar and grout?
Mortar bonds units together and is mixed stiff enough to hold a trowel ridge. Grout is fluid and is poured into block cells to encase reinforcing steel. They are different products with different consistencies and are not interchangeable.
Is mortar mix the same as concrete mix?
No. Mortar contains fine sand only and is designed for bond and workability; concrete contains coarse aggregate and is designed for compressive strength. Using concrete mix as mortar gives you unworkable joints, and mortar in a footing gives you a weak footing.
Can I add water to stiffening mortar?
Once, within the working window, in a small amount, and remixed thoroughly. Retempering repeatedly or after initial set permanently reduces strength and changes the cured colour.
Why is my mortar a different colour between courses?
Almost always inconsistent water content or inconsistent batching between mixes. Pre-blended bagged mortar exists specifically to remove that variable — measure the water the same way for every batch and the wall reads as one colour.
