I am planning to lay down edging around the lawn in my garden - leaving about 750 mm wide flower beds along the fence. All in all, I need to lay down about 23 meters of edging slabs - it will be these ones:


The idea is to dig a shallow "trench", pour a base of cement mixture to level the bottom, then set the edging blocks and add a bit more cement mixture on the sides to "fix" them to the base. Finally, add back some soil to cover all the cement. There will be about 10 cm of the blocks visible above the ground.

My question is, given the length of 23 meters (about 75 feet) and the width of the blocks of 5 cm (about 2 inches), how much cement/sand do I need to buy?

  • We can not tell you how much without knowing the cubic meters ( shallow is not enough info ). You are buy the edging slabs ? You just need to know about the foundation in the trench ? For the later you need to know the length ( 23 Meters ) X depth X width. Use a cubic meter calculator to tell you the total cubic meters of concrete you will need and then buy enough material for that amount of concrete. OR buy premixed bags, they have a specific amount of cubic feet or meters in each bag. ginifab.com/feeds/cbm/cubic_meter_calculator.html
    – Alaska Man
    Mar 23, 2020 at 22:14

2 Answers 2


Assuming 2" around the sides and bottoms, you'll need about 19 cubic feet. 5 bags of cement and 10 bags of sand should do it for you. If you come up short, go and buy some more. If you don't want to come up short, buy more first then return what is unused later. Mix 2 sand : 1 cement.


Trench area in cubic inches. Out of total width 6 inches, 4 inches are sticking out, 2 inches are in the ground.

2 X 2 X (23150/25.4) =3646.0 cubic inches.

Cement volume is one third of total volume (rest two thirds sand)

3646/3 =1215.22

convert to litres

121.522 * 0.0163871= 19.914 liters

multiply by cement density 1.44 kg per liter to obtain cement weight.

28.676 kg

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