75b-453
Plywood is an assembly of thin sheets of wood layers alternating in grain direction, glued and compressed together. There are 2 types of plywood used in construction: Interior (moisture resistant) and exterior (waterproofed). Exterior plywood surfaces are grouped into ‘grades’ ranging from A through D, with A being the highest quality and D being the lowest:
        A: Very smooth surface with patches permitted
maxresdefault
        B: Smooth surface with patches and plugs permitted
ccpts
        C: Plugs permitted and knot holes up to 1″
rp4-2
        D: Knot holes permitted up to 2-1/2″ wide
cd-sheathing-004-600
Exposure 1 plywood is fully waterproofed but is not rated for permanent exposure to moisture. Exposure 2 is an interior plywood type with intermediate glue which is only water resistant. Structural grade plywood is specially made for engineered applications like box beams.
2470868_orig
Types and prices of plywood available will fluctuate based on geographic and economic conditions. Below is a more detailed explanation of surface grades and associated allowable quality:
        A – Both Veneers virtually free from defects
        A/B – Reverse veneer only a few small knots or discolorations
        A/BB – Reverse side allowing jointed veneers, knots, plugs.
        B – Both veneers only a few small knots
        B/BB – Reverse side allowing jointed veneers, large knots, plugs
        BB – Both sides allowings jointed veneers, large knots, plugs
        X – Knots, Knotholes, cracks, etc.
Below are certain uses based on different grades:
        AA-AD – Interior – Cupboards, shelving, paneling, furniture.
        BB Plyform – Concrete form plywood
        CDX – Wall and roof sheathing, primarily exterior
        AA-AC – Exterior – Fences, signs, siding, soffits, etc.
greencore-panel
The wood used for plywood is either softwood or hardwood. Softwood is most common for construction and is made up commonly of Douglas-Fir or Spruce-Pine-Fur (SPF). 4×8 sheets are the most commonly manufactured size with 4×10 sizes also readily available. Roofing plywood is commonly at least 5/8″ thick and subfloor sheathing is commonly 3/4″ minimum thick. Subfloor sheathing is commonly tongue and groove which keeps the boards from shifting up and down at the joints.
Advertisements