FOR IMMEDIATE RELEASE
Contact: Technical Director - 847/480-9138
October 19, 2000
New Concrete Slab Configuration Raises Concerns Among
Sports Flooring Installers
NORTHBROOK, IL - Concrete slab configuration
is very important in
the success of a new maple floor installation. Placing
a below-slab vapor barrier directly beneath the concrete
slab is proper and typical.
Placing any type of fill material between the below-slab
vapor barrier and the concrete slab may cause moisture-related
problems with the
finished maple surface.
The Maple Flooring Manufacturers
Association (MFMA) requires the general contractor
to provide a concrete slab troweled smooth and flat to a tolerance
of 1/8" in
a 10' radius, subject to the approval of the MFMA wood flooring contractor.
By placing sand between the vapor barrier and the slab, a flatter concrete
slab with less initial curling can be produced. However, this new configuration
allows the sand to possibly act like a sponge -- trapping moisture within
the sand layer during the concrete pour. Over time,
trapped moisture can migrate
up through the concrete slab and cause moisture-related difficulties with
subfloor components and the finished wood flooring
surface.
Concrete moisture content emission levels are also
specified by the MFMA. When using a calcium chloride
concrete moisture test, an acceptable
level of vapor emission is 4.5 lbs. or less over
a 24-hour period. Slab construction methods which place
a layer of sand
between the
concrete slab and the below-slab vapor barrier allow
the slab to dry out more quickly. A calcium chloride
concrete moisture test taken
on a concrete slab where sand has been installed
between the slab and the below-slab vapor barrier can
give false vapor emission
rates
due to variations in the rate of moisture migration
from the sand through the concrete slab.
For more information
regarding variations to MFMA's recommended concrete
slab configuration, contact MFMA's Technical Director at 847/480-9138
or e-mail mfma@maplefloor.org.
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