Mr Sandman wrote:

Yes around the side i suppose. Underneath i don't know if it'd handle
the compression. Can anyone work out the compressive load of 2 meters
of water? i.e. using supabloc 7, could it cope with the weight?
http://www.tarmac.co.uk/TopBlock/DuroxSupabloc7.aspx

Steve

Huh? That's easy. A cubic meter weighs near as dammit a tonne. (varies
with temperature, but not enough to matter) so you are getting 2 tonnes
per square metre, 20KPa or 1/5 of an atmosphere. 3 PSI even.

What? The blocks are in N/mm^2! that's a barsteward unit if ever I saw
one!

One Pascal is one Newton per square metre, so 7.3N/mm^2 is 7.3MPa.
Those blocks are easily strong enough.

Whether they'll still insulate when they've soaked up ground water for a
couple of years I have no idea.

Andy