Porphyry is a paving stone that is growing in popularity in the U.S.. Used for centuries in Europe and othe parts of the world, it makes an indelible impression on visitors from this country – unlike any other paving stone in the world. Porphyry is so desirable that post war concrete paver manufacturers haved tried for decades to duplicate its appearance.
Rapid post war growth is also to blame for the deterioration of the knowledge of how to set variable thickness paving stones like porphyry. Durable solutions like porphyry were sacrificed for speed and unskilled labor. These materials lack the beauty and durability of porphyry.
Guidelines for Choosing a Porphyry Installer:
- The installer must provide references for installations that have been in place for 5 or more years.
- The installer must have worked with variable thickness porphyry and not the templated mesh-mounted variety. Mesh mounts are not true porphyry in the traditional sense.
- The references provided should be reviewable. It is preferrable to be able to visit the sites in person, to see first hand how the workmanship is holding up.
- The installer should be able to set traditional porphyry designs like fans, arcs, and circles – as well as dimensional pavers in a running bond.
- Porphyry setting requires the use of string lines, particularly when setting pattens.
Setting porphyry pre-dates modern paving materials and has origins back to the Roman Empire. The Romans were among the first to engineer a base using interlocking stone in a layerd base to provide stability and drainage. These principles still apply today – regardless of paving material.
The key difference between setting porphyry and setting other unit pavers are the top two layers – the bedding layer (sand or dry pack mortar) and the porphyry itself. Both are variable in thickness – unlike concrete pavers or brick. These top two layers are where the porphyry skill set is required.
Experienced porphyry setters will not screed the bedding layer. It is left variable and the setter will work in the setting bed, away from the previously set stone. The setter will add or subtract bedding material as required by the thickness of the individual stones being set. The typical method is to tap the stone into the setting bed, leaving it just above grade so that it may be compacted to achieve interlock. An example of this can be seen in the video below.
What to Avoid in Choosing a Porphyry Installer
The following factors demonstrate a lack of knowledge of porphyry setting techniques:
- An installer who claims that porphyry cannot be level or meet modern ADA standards
- An installer who wants to sort the stone or treat it like a gauged concrete paver
- An installer who tries switch the porphyry to another material
- An installer who does not use string lines.
Installation training by the ICPI provides an excellent background for base preparation but is not enough training for porphyry. Seek a masonry company that has a background in installing variable thickness paving like flagstone.
Finding a qualified installer is critical to a successful installation. Experienced stone masons have the best training and background for porphyry but a paving company with training in variable thickness material will suffice.