Question 1

How much mortar do I need per 1000 bricks?

Accepted Answer

Plan on about 7 to 8 bags of 70 lb pre-mixed mortar per 1000 standard modular bricks (7 5/8 by 2 1/4 inch face) with 3/8 inch joints. That equals roughly 8 to 9 cubic feet of mortar. Larger bricks or wider joints push usage higher, while pavers laid tight can use as little as 5 bags per 1000.

Question 2

How much mortar do I need per 100 concrete blocks?

Accepted Answer

For standard 8 inch CMU, plan on about 3 bags of 70 lb mortar per 100 blocks. 4 inch blocks need ~2 bags, 6 inch blocks ~2.5 bags, and 12 inch blocks ~3.5 bags per 100. Add 5 to 10 percent extra for retempering and edge waste.

Question 3

What is the difference between Type N, S, M, and O mortar?

Accepted Answer

Type N is the most common all-purpose mortar (1:1:6 cement:lime:sand) for above-grade walls. Type S (2:1:9) is stronger and used below grade or for high-load walls. Type M (3:1:12) is the strongest and is used for foundations and retaining walls in contact with earth. Type O (1:2:9) is soft, used only for interior non-load-bearing repointing of historic masonry.

Question 4

How do I mix mortar from scratch?

Accepted Answer

For Type N mortar, mix 1 part Portland cement, 1 part hydrated lime, and 6 parts mason sand by volume. Add water gradually until the mortar holds its shape on the trowel without slumping. A typical batch using 1 bag (94 lb) of Portland cement plus 1 bag of lime and 600 lbs of sand yields about 9 cubic feet of mortar - enough for roughly 100 standard 8 inch CMU blocks.

Question 5

How long can I use mortar after mixing?

Accepted Answer

Mortar should be used within 90 minutes of initial mixing in normal temperatures and within 60 minutes if temperatures are above 80 degrees F. You can retemper (add small amounts of water and remix) within that window if it stiffens, but never add water after the initial set has begun. Cold weather slows setting but mortar should not be placed below 40 degrees F without admixtures or heated enclosures.

Question 6

How much sand do I need for mortar?

Accepted Answer

If mixing from scratch, plan on about 0.5 to 0.6 cubic yards of mason sand per 1000 standard bricks, or about 1 ton (~20 cubic feet) per 100 standard 8 inch CMU. Mason sand should be clean, well-graded, and meet ASTM C144 specifications. Avoid play sand or beach sand, which are too fine and contain salt.

Unit	Coverage (80 lb bag)	Joint Width
8 x 8 x 16 CMU	~27 blocks	3/8 in
Standard brick	~40 to 50 bricks	3/8 in
Modular brick	~50 to 60 bricks	3/8 in
Stone veneer	~8 to 10 sq ft	1/2 to 1 in

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