25
Important:SincethereisnorebricksetalongthetopoftheIBVreboxopening,whensettingthenoncombustiblefacing
material(coderequiredandsuppliedbyothers)ontothedrywallacrossthetopofthereboxopeningtherewillbeagapbetween
thebackofthenoncombustiblenishmaterialandtheroughfrontfaceoftheIsokernSmokeDome(Figure29).
BesuretollthisgapwithEarthcoreMortar(orsimilarnoncombustiblegrout)inconjunctionwithplacementofthecode
requirednoncombustiblenishfacingmaterialthatissetacrossthetopofthereboxopening.
WARNING: Avoid false chimneys.
Important: Failure to seal any gaps between the front face of the IBV and the back of the noncombustible nished facing
material will create what is known as a “false chimney” or “secondary chimney”. A “false chimney”, in this case is the narrow gap
(mentionedabove)betweenthebackofthenoncombustiblefacingmaterialatthetopofthereboxopeningandtheroughfront
oftheIBVsmokedome.Ifleftunlledthisgapcreatesa“falsechimney”whichcancausearehazardbydrawingconsiderable
heatoutofthereboxandintothespacebehindthenoncombustiblenishfacingandfromthereupintothewallcavitybehind
thedrywallorothersheathingmaterialthathousestheIsokernreplace.
Finish Facing Detail
Important: Grout
this gap with
Earthcore Mortar
to avoid creating
a “false chimney”.
Combustible
floor system
(non-insulation)
Hearth Extension
(Noncombustible)
Figure 29