Can I lay pavers/brick/flagstone over my crappy old concrete walk?

When someone asks me, “can I lay pavers/brick/flagstone over my crappy old concrete walk?” I think about the difference between frugal and cheap. Frugal is shopping at stores like Aldi or Lidl. Cheap is shopping at stores like the grocery outlet in El Cajon, where I purchased – and ate, don’t judge – Mr T cereal… in 1998. 

Sure, it had been discontinued for years at that point, but 50 cents a box is 50 cents a box. Trying to save money in the wrong place on your hardscape projects can cause more issues than an upset stomach. 

Here’s a great example of what can happen when you lay a new brick sidewalk over top of an old concrete walk. 

Do you see that line where one row of brick is heaving upwards and away from the adjacent one? The homeowner definitely noticed and asked us what we could do about it. To figure out the fix I had to find the cause. It was as easy as removing a couple of the bricks.

See that big yawning chasm in the concrete underneath? That was a weak point in the slab. More than likely, the ground under one part of the walkway settled or eroded. Because concrete doesn’t want to span holes or voids unsupported, it did what concrete does and it cracked. That crack telegraphed itself all the way up to the brick. Because the brick was dry set on top of the slab it just got pushed up. If the brick had been mortared to the slab, the joint may have cracked or it may have even cracked across the brick itself. 

Ok what now? 

Diagnosing the problem was the easy part. The fix isn’t quite so straightforward. One option would be a technique called mudjacking. The contractor digs along the side of the slab to find the void, and then pumps it full of concrete until the slab is leveled out again. It’s not cheap, and there’s no guarantee that this same problem won’t happen 15 feet farther down the walk. 

We could also cut out and repour that section of walkway, and replace the brick. That still leaves us with the problem that there’s no way to guarantee the portions of the walkway we didn’t repair. The only way we could guarantee the result would be a complete redo of the entire walk. That’s because at the end of the day, we have no way to know if the slab is thick enough along the entire length. Based on what we saw here, there’s probably no reinforcement in the slab to help carry the weight. 

This has been a long-winded answer to the question, can I lay pavers/brick/flagstone over my crappy old concrete walk? The bottom line is that you can, but you’re taking a risk. As accident prone as I am (Culpeper’s hospital needs a jello punch card or something), I’d rather spend a little more up front for a safe and durable walkway.