We generally do not recommend laying thin ceramic or porcelain tiles over fiberglass grating since these tiles do not have enough internal strength to support live loads when dry-laid over a hard surface. Micro movements over time can cause the material to fracture.
Instead we recommend using 3/4″ thick structural porcelain pavers. The thicker pavers are specifically designed for exterior use, have an anti-slip finish and are much less susceptible to impact damage and/or breakage than thin tiles. Normally 3/4″ porcelain pavers can be laid directly over adjustable height pedestals to build elevated decks, but in some circumstances e.g. if using small pavers like 8″ x 8″ porcelain cobblestones, a fiberglass base may be necessary.
Tile spacers should be used with all porcelain paver installations to prevent the possibility of chipping on the edges.
We recommend laying small porcelain pavers, such as 8″ x 8″ cobblestone tiles over a recycled rubber underlayment placed over the fiberglass panels and using small tile spacers to keep the cobblestones consistently spaced and aligned. 1/8″ thick recycled rubber underlayment is available in rolls 4’ x 50’.
Normally the gaps between cobblestone pavers are left open. However, if preferred, gaps can be filled with polymeric sand.
For larger porcelain pavers, we recommend using rubber pads with inbuilt spacer tabs to raise the pavers slightly off the fiberglass panels. These pads ensure correct spacing and minimize noise transmission. This method of installing porcelain pavers can be especially useful with narrow plank style pavers (8″ or 12″ wide) instead of using a pedestal supported rail system, as it also provides fall through protection.
If sound deadening is not an issue, porcelain pavers can be laid over a geotextile mat using small tile spacers to ensure consistent tile spacing and alignment.