With Concrete Sand being the traditional choice for non-permeable installations for interlocking pavers, there is an alternative option to choose from that we opt for in every installation except for concrete overlays.
Since I started in this industry in 2007, I was introduced to High Performance Bedding or HPB as a bedding layer aggregate while working at a supplier. Looking back, I was lucky to be able to be introduced to this product so early in my career and how beneficial it is for hardscapers. However, even at this time it was not being embraced by contractors and we still saw more traditional contractors sticking with stone dust as their preferred bedding material. Since this time, I have seen HPB become increasingly embraced as it has been in my business.
High Performance Bedding (HPB)
High Performance Bedding or HPB is an angular crushed aggregate 1mm to 8mm in size with a maximum nominal size of 6.7mm or 1/4″. It is a washed aggregate with little or no dust fractions making it a clear stone allowing water to flow through it with minimal resistance. In its loose state, it does reach up to 90% compaction with the remainder compaction percentage being achieved with mechanical compaction. High Performance Bedding is a registered Trademarked name by Dufferin Aggregates, a division of CRH Canada Group Inc, filed in 1998 and approved in 1999.
HPB is specifically used as a bedding layer under interlocking pavers and other material to build pavement structures. Though I have seen contractors rely on it for other uses, including for the entire base and bedding material for a project, it is specifically to be used as a bedding layer because it does not have the bearing ability of other aggregates that would be used for the base material.
HPB vs Sand
We use HPB almost exclusively in our business as a bedding material under our paver installations and even for our levelling course of our retaining wall because it is the superior product when compared to Concrete Sand in our opinion.
HPB is used as the bedding material for permeable and open graded base installations because it does not wash through the voids of the 3/4″ crushed stone as a sand would. We opt for open graded bases for raised patios and projects that do not directly tie into a traditional base like a front walkway tying into a driveway. By using this base installation, we can continue to work in rain days where we would not be able to install a traditional base with a Concrete Sand bedding layer. Concrete Sand washes out easily with rainfall and creates imperfections in the surface forcing you to have to fix prior to laying pavers. You will not experience this same washout of material when installing HPB.
This is also beneficial when a project is completed, as the bedding layer will not washout over time causing the shifting and sinking of pavers. This is especially noticeable in raised patio applications where gaps between wall units can cause the fines of a Concrete Sand to wash through. HPB with its angular crushed larger aggregates when compared to sand allows for the material to lock together and reduce the amount of washout.
Additionally, we recommend it for the installation of synthetic base or paver base panels. This is because if you use Concrete Sand as the levelling layer, it would need to be compacted prior to installing the paver base panels on top. This causes imperfections in the bedding layer and adds a step where you would need to further level the surface before installing the paver base panels. Using HPB does not require this compaction step.
One note of further comparison between HPB and Concrete Sand as a bedding layer is that Concrete Sand is the only approved bedding material for a non-permeable installation for interlocking pavers by ICPI. This is because of the interlock that is achieved upon final compaction and consolidation of the jointing compound. During this phase of the project, the Concrete Sand pushes upwards between the joints of the pavers while the jointing compound consolidates to the bottom of that joint creating interlock. However, with pavers being produced with increasingly wider joints, HPB is able to achieve this movement upwards as Concrete Sand would.
High Performance Bedding Installation
Installing High Performance Bedding as a bedding layer for pavers is much like concrete sand, only it has several benefits in comparison as described above. In fact, it is easier to work with than concrete sand as a bedding layer. Screeding HPB follows the same steps as with a Concrete Sand installation as the bedding layer.
We use it in our business only as the bedding layer, but Dufferin Aggregates approves it for several other uses including drainage stone behind retaining walls, around drain tile, French drains, catch basins, and swimming pools. However, in these drainage situations with the exception of swimming pools we opt for a 3/4″ angular crushed clear stone.
High Performance Bedding or HPB stone has changed our installation methods in our business. It makes our job easier as an installer and continues to help take advantage of rain days where we would not have been able to install. It is an aggregate that we will continue to rely on in our hardscaping business.