MacKinnon Reid has been installing Unit Pavers (also known as interlock or slabs) since 1984. Unit Pavers are made of concrete called precast in 2 different recipes such as dry cast or wet cast. Dry cast is more durable to our weather, colours and dimensions are more precise. The longevity of your pavers staying level will be based on your gravel base. We use different techniques but the main reasons for longevity are geotextile, depth of excavation and well compacted gravel base. We use a compactor that weigh about 400 pounds. We compact only 3 to 4 inches at a time.