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Concrete Ponds - Calculating Sealant

21st Nov 2019

To calculate the amount of G4 concrete sealant required for your pond you need to work out the internal area of the pond. For this you will need to know the following dimensions of the pond in metres;

  • The length of the pond (L),
  • The width of the pond (W) and
  • The average depth of the pond (av. D).

It is easier to imagine your pond as an exploded diagram, then use this to work out the surface area of the sides and ends and the bottom, and then add them up.

The formula for internal surface area is;Bottom 2 Sides 2 Ends, or(L x W) Building a Pond (2 x D x L) Building a Pond (2 x D x W)E.g. a pond is 5 metres long, 3 metres wide and has an average depth of 1 metre;Internal Area

= (L x W)  (2 x D x L)  (2 x D x W)

= (5 x 3)  (2 x 1 x 5)  (2 x 1 x 3)

= 15 

= 31 m2And for working out the amount of G4 you require to paint the pond…For a pond calculated to have an internal area of 31m2

Clear Finish required

= 550g clear per m2

= 550g x 31= 17050g (or 17.05 kg) of Clear G4

Black Finish required

= 410g clear per m2

= 410g x 31= 12710g (or 12.71 kg) of Clear G4


= 400g black per m2

= 400g x 31

= 12400g (12.4 kg) of Black G4Once your pond has been waterproofed the edging and wall tops can be completed, remembering to seal any concrete used in their construction.