DIY Doctor UK DIY Forums

[b]Can standard paving slabs stood on edgebe used to create a retainging garden wal up to 300 mm high? if so how deep should they be set in the ground? how long should ordinary concrete take to harden to be inpenetratable to pushing a car key into it. iIf I can push my car key into it after 5 days is this good concrete[/b]

Yes, but the slabs need to be the 50mm thick kind really and need 50% of them in the ground, ie 600mm slabs for 300mm showing and you should not be able to push your keys in after 1 day never mind 5.