Plywood Flashcards
plywood: graded two ways
span rating,
quality of face veneer.
plywood: graded for structural applications.
span rating
span rating consists of 2 #’s
max spacing for roof supports,
then max spacing for floor supports.
span rating req’s
face grain perpendicular to supports, and continuous over 3 supports.
span rating for structural use, also classified by
species of wood (5 groups)
Span rating:
Structural I uses which wood groups:
only group 1
Span rating:
Structural II uses which wood groups:
groups 1,2,3
quality of face veneer: N
natural finish,
made from all heartwood/sapwood.
free from defects,
but only special order.
quality of face veneer: A
smooth + paintable,
few knots/defects,
best commonly available.
quality of face veneer: B
allows for plugged knotholes,
but has smooth surface.
quality of face veneer: C
allows small knotholes and some splits.
quality of face veneer: D
larger knotholes.
if plywood to be outdoors:
should have special glue spec’d
plywood is available in these special panels:
patterned panels,
marine plywood,
smooth paper surface.
lateral support, increase rigidity, base for ext. finishes.
sheathing
sheathing typ material:
plywood/particleboard
where lateral stability not critical, this sheathing mat’l may be used:
insulated sheathing
mixed in binder and formed under pressure:
particleboard
particleboard available in varying:
densities
particleboard typ. prefered for backing/framing of finish carpentry/woodwork bc:
bc less $/more dimensionally stable than plywood.
engineered panel product,
manufactured from precision-cut wood strands
OSB
oriented strand board
OSB strand dims:
arranged in:
max 4” long,
0.0027” thick.
arranged in layers @ right angles,
OSB sizes
from 4x8’ to 8x28’
primary OSB strength is noted visually by:
orientation of chips on the face layer,
typ parallel to length of panel.
OSB disadvantage:
more susceptible to delamination than plywood.
wood particles,
reduced to fibers in moderate steam pressure vessel,
combined w a resin,
bonded under heat and pressure.
medium-density fiberboard (MDF)
quality: smooth, uniform, dense surface.
uses: painting, veneers, high-pressure laminates.
medium-density fiberboard (MDF)
*most dimensionally stable of mat-formed panel products.
medium-density fiberboard (MDF)
inter-felted fibers,
consolidated under heat + pressure,
to a density of 31 lb/ft3.
hardboard
process to make hardboard harder, stiffer, heavier:
temper
