One of our friends just had their brick patio repaired by a contractor and after about a week and some hard rain it seems that there is some out of level and sinking problems in the center of the patio.
He says that the patio is made from brick pavers laid in a basket weave pattern. The workers laid them on top tamped and leveled sand, and then filled sand in around them. After a few days of heavy rain, a low spot has developed.
After further questioning it seems that they did take care to use general procedures when relaying the patio but often when you are working with patios or walkways that have been established for some time the mere resetting them will cause you problems. This is because over time the soil below has eroded and it is not of a high enough compaction rate to allow for resetting of the same or different materials.
How To Set a Brick Patio the right way
Whether you are installing a new or resetting an established patio or large walkway that is formed out of brick or other paving materials the first thing that you must do is establish a firm base.
Normally the best way to do this is to dig down far enough that you remove all of the topsoil and lose materials. You can not have organic material under your walkway like roots, grass or weeds or have soil that is not firm or it will fail.
I would suggest that for most people that you dig at least a foot deep and then fill the hole with a gravel that comes in a variety of stone sizes. It is normally reffered to as 3/4″ minus which means the largest stones will be about 3/4 of an inch big and smaller stones will be included and help to lock it all together.
Once you have the stone in place you need to use a plate compactor. You will need to compact the stone long enough that it establishes a very firm base.
Like I said you want to remove about a foot of material but remember that the top 3 inches or so will be used for your paving material so you are not filling the entire hole with stone. You can also use less stone if the soil in your area has a high compaction rate and you will know this just by digging in it. The first 4 inches or so will come out really easy and then when you hit higher compaction soil it will be hard as a rock and made of clay and sand.
Once you have established your base you can then add sand and then lay your paving material over the sand.
Again the depth of the hole and the amount of gravel and sand you will need will be different than everyone else. This can even change from neighbor to neighbor but the most important thing is that you start with Gravel and then compact it with a plate compactor and then you can add more stone where necessary and use sand or maybe stone dust to lay your paving materials.
Some people suggest that you add a weed blocker fabric but it is not really necessary. Your paver joints should be tight and a final pass of sand should be swept into the cracks between the pavers to lock them in place.
Many contractors will add sand to the top of the pavers and then plate compact the pavers into place. This depends on many factors but I would not suggest it on thinner concrete pavers as they will normally crack.
If you are in doubt always contact your supplier for their recommendations on how to prepare your soil for paving materials.