7. PLYWOOD-ON-SLAB SYSTEM.
This is very easy to find in any store
in the bay area or the san Francisco
bay in fact from san Jose to Richmond
California you be able to find this
Sub floor material plywood on slab system
uses 3⁄4" or thicker grade exterior
plywood or sub floor material over the
appropriate vapor retarded. Loose lay
3⁄4" plywood panels over entire
floor a lots of the houses in the bay
area from redwood city to el Cerrito
already have this sub-floors but the
new house that need hardwood floors
from san Jose to high rises in san Francisco
may need it . Laying plywood on a diagonal
to the direction of the finished floor
will help prevent cracks associated
with panel edges. Stagger plywood and
joints every 4' by cutting the first
sheet of every other run in half. Leave
3⁄4" space at all wall lines and
1⁄4" to 1⁄2" between panels.
Cut plywood to fit within 1⁄8"
near and around door jambs and other
obstructions where finish trim will
not be used this will ensure the quality
of the hardwood floor installation and
after the hardwood floor refinish with
oil base or water base. Fasten the plywood
with a powder-actuated concrete nailer
or hammer-driven concrete nails. To
be sure to flatten out the plywood,
start at the center of the panel and
work toward the edges. Use at least
nine nails per panel or more to fasten
securely. An alternate method is to
glue the 3⁄4" plywood or hardwood
floor sub-flooring over the vapor retarder
systems which include the cut-back mastic.
Cut the 3⁄4" plywood into 4' x
4' squares or 16” x 8’ planks, score
the back 3⁄8" deep on a 12"
x 12" grid, and lay panels in the
cut-back mastic applied with a 1⁄4"
x 1⁄4" notched trowel (35 sq. ft.
per gal.). Remember to stagger the wood
floor and the panel wood joints by 2
ft.
SCREEDS SYSTEM.
This system uses as a nailing base flat
is also normal in the great bay area
from hardwood floor refinish in Berkeley
California, to buffing floor in Sunnyvale
California , dry 2" x 4" screeds
of Group 1 density hard wood (sometimes
called sleepers) of random lengths from
18" to 48", as a nailing base.
They must be preservative treated with
a product suitable for interior installation.
After treatment screeds must be dried
to a Moisture Content of 12% or less,
if saturation with water is involved.
Screeds are laid on their flat face
in rivers of mastic with screed runs
12" on center at right angles to
the direction of the finished floor.
Sweep the slab clean, prime with an*
asphalt primer and allow to dry. Apply
hot (poured) or cold (cut-back) asphalt
mastic and imbed the screeds. Stagger
joints and
lap ends at least 4"and leave 1⁄2"
space between lapped edges. Be sure
there is enough mastic for 100% contact
between screeds and slab. Leave 3⁄4"
space between ends of screeds and walls
with a continuous run of screeds at
end walls. Over the screeds lay a 4-
to 6-mil polyethylene vapor retarder
with edges lapped over rows of screeds.
Avoid bunching or puncturing it is not
a great idea when you have a brand new
hardwood floor installation, especially
between screeds. The finish flooring
will be nailed to the screeds through
the film. The system with screeds spaced
12" on center and a moisture retarder
without a sub floor is satisfactory
for all 3⁄4" Strip Flooring and
Plank Flooring less than 4" wide.
Plank Flooring 4" and wider requires
the Plywood-On-Slab sub-floor, or screeds
plus a wood sub-floor, to provide an
adequate nailing surface. The sub-floor
over screeds may be 5⁄8" or thicker
plywood, 3⁄4" OSB (performance
rated), or 3⁄4" Group 1 dense softwood
boards or
equivalent no wider than 6". If
sub-floor boards are used over sleepers
or screeds, allow 1⁄2" spacing
between boards.
NOTE: When area moisture conditions
are considered high (some areas in the
bay area like san Francisco sometimes
hardwood floors installation is south
san Francisco or Marin city) use the
vapor retarder glued directly to the
slab system in addition to or in substitution
for the film draped over screeds you
almost there to start you hardwood floor
installation.
