In our previous post, we were able to establish that we need 0.03 m3 of mortar to lay one square metre of 9 inches hollow block wall. If you missed the post, or wish to know how we arrived at that value, follow the link below.


How to Calculate the Quantity of Mortar for Laying Blocks


The post has some set backs in the fact that it was not simplified to the most basic level. In this post, I wish to clearly establish a value that can be appreciated on site for all construction purposes.

The typical mix ratio for mortar on construction sites in Nigeria is 1:5 (1 bag of 50 kg cement to 10 head pans of sand).

Therefore, the quantity of cement required per cubic metres is given by;
1/6 x 1440 = 240 kg/m3
For wet mortar, use 1.30 x 240 = 312 kg/m3

NB: We are using a factor of 1.30 to account for shrinkage in volume when water is added to the dry mix.

Therefore, the quantity of cement required per m3 of mortar = 312/50 = 6.24 bags of cement



Quantity of mortar required per 1 m2 (10 blocks) of wall = 0.03 m3
For 5 m2 (50 blocks) of wall = 0.15 m3

Therefore, if 6.24 bags if required in 1 m3 of mortar, then 0.936 bags of cement is required in 0.15 m3 of mortar.

By inference, we can say that we need 1 bag of cement to lay 50 pieces of hollow 9 inches block (i.e 5 m2 of wall).

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