One layer high breeze blocks to raise height of tunnel question.

[Bluenowhere]

You would know if they are the dense ones (generally they are called concrete block in the building trade if you want to buy some) they are really heavy, really I don’t fancy carrying this very far heavy. If you lifted then in and out of your car boot without a massive struggle they were probably breeze blocks (the blown type). If you ask for breeze blocks in a diy or builders merchant you will get the lighter blown type.