QUESTION

I have heard that tiles can be installed a raised pedestal floor system on an exterior application, so that it will be level and it will allow water to drain below it. Can porcelain tiles be installed this way?

ANSWER

Historically pedestal floor installations were used to install 2" thick or thicker precast concrete pavers or natural stone tiles.  The floor could be level and the gaps between the pavers would facilitate for water to drain below.  The substrate beneath the tiles would be properly slopped to a drain with a waterproof membrane over it durable enough to take the weight of the pedestals with the weight of the tiles and the foot traffic it is subjected to.  The tile industry is working on developing a pedestal installation standard for 2cm thick porcelain tile, but at this time there is not standard.

The key to the installing a 2cm (3/4") porcelain tile is that you should install them on a plastic tray that sits on the pedestals at each of the 4 intersecting tile corners.  Sometimes there will be an added pedestal under the center of the tile.  The pedestals are adjustable and somewhat self-leveling, but you do have to add shims for slight adjustments because the pedestal cannot wobble at all.  The waterproof membrane has to have a high Shore A hardness so the pedestals don't sink into it.  The concrete substrate should be sloped 1/4" per foot to a proper drain with the capacity to take the potential volume of water from rain and washing down.  Critical to the installation is making sure the perimeters of the installation are well anchored in place to constrain the tile assemble so it can't push out as it is subjected to different concentrated loads and traffic.

It is important that the end-user monitor the floor and if they get any wobble tiles they need to repair them immediately or someone could be hurt.  For hurricane climatic conditions there are pedestal anchor systems that can lock the tile down so it can resist the uplift of wind.