A.Contributing editor Michael
Byrne, moderator of the JLC online tile forum and an industry
consultant in Los Olivos, Calif., responds: Unless there
is frequent precipitation that makes it impractical, I usually
build tiled decks so that the finished floor at the threshold
is level with — or slightly below — the interior
floor. Since this detail works best with outswinging doors that
don't have an integral threshold, the door must have an
effective sweep to prevent water from blowing in.
For a true barrier-free installation in a dry climate, I
eliminate the threshold completely and separate the interior
and exterior tiles with a movement joint at the doorway. In
wetter climates, or if the deck is regularly exposed to wind
and stormy weather, I use a stepped threshold to better resist
leaks (see illustration). I typically have these thresholds
fabricated out of a durable impervious stone, like granite, in
a profile that provides weather resistance while meeting code
requirements.
The exterior waterproofing should be joined to the threshold
with an appropriate long-life sealant. Water will still
occasionally get past the threshold, but this shouldn't be a
problem if the interior floor is covered with tiles installed
over a waterproofing membrane.
However, if the interior floor is covered with wood strip
flooring or another absorbent material, a flush deck is
probably a bad idea. Instead, the deck should be designed so
that there is a full 4- to 7-inch step up to the threshold. The
exterior deck membrane will then resemble a shower pan, with
upturned walls and the upturned membrane flashed and sealed at
the threshold to prevent wicking.