Transcript (en)

Why do many front walkways in American homes look so simple, and even the repair looks like they are just pumping foam underneath? But the final result is surprisingly good. Even a badly uneven slab can be lifted back into place. Many people see this step and think it is ridiculous. Can this foam really lift such a heavy concrete slab? The answer is yes. This polyurethane lifting foam expands with a lot of force. But if the concrete has already cracked into several pieces, the repair becomes much harder because the worker cannot lift only one side. For a cracked walkway like this, these three slabs need to rise at almost the same speed. After the height is adjusted, the worker also has to seal the cracks with caulk. If the concrete slab is larger, one hole is not enough. The worker has to drill several small holes, one by one, so the foam can spread evenly under the slab. Otherwise, it may only push up one single point. Compared with breaking out the whole concrete slab and pouring a new one? This method may cost around $100, and it can bring the sunken walkway back to the same height. If it were you, would you tear it out and rebuild it, or spend less money and lift it with foam?