USG Levelrock Floor Underlayment Finished Floor - Manual (Page 3)

Substrate requirements for
Levelrock Floor Underlayment
L
eveLrock
floor underlayment must be applied to a relatively dry substrate . In the case of new
wood subfloors, any moisture from the subfloor has typically dissipated into the environment .
However, where the underlayment is poured over structural concrete or concrete planks, the job
scheduling may result in the subfloors being left open to the weather and will absorb moisture
from rain and/or snow . In addition, in order to enable a concrete subfloor to qualify for LEED
®
credits, additives are sometimes used which can retain moisture . Therefore, a moisture test
(calcium chloride test method ASTM F1869* or ASTM F2170 relative humidity test) should be
conducted on the concrete substrate . The recommended limit for application of L
eveLrock
floor
underlayment is 5 lbs ./1000 sq . ft . in 24 hrs . However, the floor covering manufacturer may
have stricter standards and these will take precedence over those provided here . USG’s limit
for relative humidity is 75%-80% or less .
Note *The ASTM F1869 calcium chloride method is not an acceptable method for checking the dryness of L
eveLrock underlayments .
Test for Dryness
L
eveLrock
floor underlayment must be dry
before installing floor covering . Normal drying
time for ¾ in . thickness is 5-7 days, with
proper ventilation/good air flow (70 °F, 50%
relative humidity) . Underlayment thickness
and drying conditions will affect drying time;
allow approximately 4-5 additional days for
each additional ¼ in . thickness . Also note that
higher humidities and cooler temperatures –
often found on jobsites – will inhibit drying .
As a general rule of thumb, L
eveLrock
floor
underlayments at their typical application
rates will dry as follows:
· 0 .5 inches:
3-5 days
· 0 .75 inches: 5-7 days
· 1 .5 inches: 17-19 days
Drafts occurring during the setting process
– usually within the first 2-3 hours after
the pour can cause dusting on the surface
of L
eveLrock
floor underlayment due to the
surface drying before it sets . However, once
the material is set, good air movement/air
exchange is encouraged to speed the drying
process . The exception to the aforementioned
drying schedule is L
eveLrock
® Q
uik
-t
op
™ and
Q
uik
-t
op ™ Gray floor underlayments . These
products have a unique technology that will
allow them to accept a floor covering 15
hours after installation . Also note that the
maximum recommended thickness for Q
uik
-
t
op
floor underlayments installation is 1 in .
responsibility for Drying
environment
L
eveLrock
floor underlayment must not be
installed unless there is a minimum
temperature of 50 °F day and night . The
general contractor must be made aware of
these conditions at the job meeting and is
Surface requirements
3