It seems that more and more people are interested in building a raised paver patio. It gives elevation, dimension, and yard separation. What most people don’t know about raised paver patios is the failure rate. In the world of hardscaping (term used to describe the installation of interlocking patios and retaining walls), raised paver patios are among the most difficult installations to pull off successfully. Here is why:
The first thing I would suggest is remove all landscapers from your bidders list. Landscapers, although this doesn’t apply to everyone of them, can typically install simple patios and hardscape projects, but building a raised patio requires a company that has a tremendous amount of experience installing only hardscape projects to understand what to do and what not to do when building a raised patio.
The number one reason for raised patio failure is improper installation of fill and improper fill material selection. Fill is the material used to fill the void between the bottom of your pavers and the ground. In most instances, if you’re building a raised patio, you will be adding a substantial amount of fill material. It’s important to never use soil/dirt. Dirt, without having VERY large compaction equipment designed specifically for the compaction of dirt, is almost impossible to compact completely. I can almost guarantee if dirt is used as any type of backfill material below your hardscape, it will settle SUBSTANTIALLY.
Limestone 411’s for paver base in raised patio’s
Limestone 411’s aka Paver Base
So what do we use for fill material? The best option, depending on your location, is angular limestone chips with dust. In most places, this type of gravel is called limestone 411’s or limestone chips and dust. This is a mixture of 3/4″ angular pieces of limestone all the way down to dust. If you only used the 3/4″ pieces of limestone, there would be a lot of air pockets created in-between each stone allowing the stones to move around and settle after time. The addition of smaller stone pieces and dust combine together to achieve a very dense fill.
I almost forgot, NEVER EVER EVER use pea gravel or allow your contractor to use pea gravel. Pea gravel (very small round pieces of gravel) has been used under concrete for years as a base fill material. Could possibly be why most concrete you see is cracked (just kidding, but who knows?). Pea gravel is a highly lazy gravel, which means, under heavy loads the pea gravel migrates into neighboring soils because its round in shape and small. If you ever paid attention to where a driveway meets a garage floor you probably observed that the driveway was much lower that the garage floor. This is caused in most cases by the pea gravel under the driveway migrating into the material below the garage floor. If there is limestone 411’s below the concrete or paver driveway but there is pea gravel below the garage floor, the limestone 411’s could work its way into the pea gravel after time. In either case, we would use a geotextile fabric for material separation. Geotextile fabric is a tensile material used in stabalizing different soils and fill materials.
How do we compact the fill material? There are a couple important things to remember when compacting limestone 411’s. Have you ever picked up a handful of dirt that was bone dry and tried to compact it into a ball? It doesn’t work so well. But, if you add just the right amount of moisture, you have the perfect mud ball. The same thing applies to compacting limestone gravel. It’s important to add moisture to the gravel before/as you compact it. The moisture helps release the air and aids by bonding the dust to the stone chips. Secondly, its important to never compact more than 2-4 inches in depth at a time using standard mechanical compaction equipment. If you are a DIY, and plan to use a hand tamp, I wouldn’t compact more than 1″ in depth at a time. Make sure and buy plenty of gloves if you plan to use a hand tamp, as you will be tamping for a really long time. That being said, I HIGHLY recommend that you use a vibrating plate compactor to compact the base especially if you’re building a raised patio.
If by now you haven’t decided to hire a professional that specializes in the installation of hardscapes, you’re a brave soul.
Proper excavation prior to installation of fill material is just as important as the selection and compaction of fill material. Most will agree that 6″ of base below a paver patio is the proper amount. However, this doesn’t mean that you don’t have to excavate if your building a raised patio. I see it all the time; a contractor builds a raised patio and doesn’t excavate below the frost line and doesn’t remove the top soil. Top soil is simply organic matter like rotted roots and leaves.
So, you should still excavate at least 6″ prior to the installation of fill material for a raised paver patio.
Probably the third most common cause for raised paver patio failure is loss of fill material. If you’re familiar with all the general paver installation steps, you know that after the fill material aka the base comes the sand setting bed. Since the particle size of sand is so small, it’s easy for the sand to fall through the cracks/joints in the walls that build the patio up. You should always use a geotextile fabric to contain all fill materials when building a raised paver patio.
These are just a few of the most common causes that raised paver patios fail. Raised patio’s are typically much more labor and material intensive making them more expensive than paver patio’s closer to ground level. I can’t recommend enough times to contact a company that specializes in these types of installations.
If you’re located in Southwest or Central Ohio, please don’t hesitate to contact us for more information or to schedule a design consultation.
Thanks for reading- Mark Rhodus, President Two Brothers Brick Paving, LLC
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