Common Building Materials Reference

Why this matters

Every service trade encounters framing, drywall, plywood, insulation, exterior cladding. The tech who recognizes materials + understands the structure works around them safely + correctly. This is the field card.

Lumber sizes (nominal vs actual)

Nominal = name; actual = real dimension after milling.

1×2 (3/4 × 1-1/2 furring); 1×3 (3/4 × 2-1/2 lath); 1×4 (3/4 × 3-1/2 sub-trim); 1×6 (3/4 × 5-1/2 boards); 1×8 (3/4 × 7-1/4); 1×12 (3/4 × 11-1/4 shelving); 2×4 (1-1/2 × 3-1/2 studs); 2×6 (1-1/2 × 5-1/2 exterior R-19); 2×8 (1-1/2 × 7-1/4 floor/roof); 2×10 (1-1/2 × 9-1/4 longer spans); 2×12 (1-1/2 × 11-1/4 beams); 4×4 (3-1/2 × 3-1/2 posts). Standard lengths 8, 10, 12, 14, 16 ft; special 20, 24 ft.

Lumber grades

Construction grade: standard framing; SPF (spruce-pine-fir).

Standard + better (Stud grade): studs specifically.

#2 + Better: visible OR finish work.

#1 + Better: appearance grade; few knots.

Select: best appearance.

Pressure-treated (PT): green/brown stain; ACQ OR CCA copper preservative. ACQ-treated since 2004 (CCA banned residential 2003).

Cedar / redwood: natural rot resistance; trim + exterior.

Engineered lumber

LVL (laminated veneer lumber): thin layers of wood + adhesive; beams, headers; stronger + straighter than solid lumber.

Glulam (glued laminated): similar but larger glued layers; structural beams.

PSL (parallel strand): long strands + adhesive; high-strength beams.

I-joist: I-beam shape; deep web + flange; floor joists; stronger + lighter than solid lumber.

LSL (laminated strand): short strands; medium-strength.

Engineered wood I-joist (TJI): trade name; common floor framing.

Plywood

Sheathing (exterior wall, roof): 4 × 8 sheets; 1/4", 3/8", 1/2", 5/8", 3/4".

OSB (oriented strand board): 4 × 8 sheets; replaces plywood in much modern construction; cheaper + similar strength.

Underlayment (1/4" plywood): smooth surface under flooring.

Marine plywood: water-resistant adhesive + face; boats, exterior.

MDF (medium-density fiberboard): smooth + paintable; cabinet + trim; very heavy.

Particleboard: cheap; sub-flooring + cabinet; not for moisture.

Wafer board: similar to OSB; older.

Drywall

1/2" standard: most common interior wall + ceiling.

5/8" Type X (fire-rated): the garage separation is a two-part rule and the halves get merged. The IRC asks for not less than 1/2" gypsum board on the GARAGE SIDE of the wall separating a garage from the dwelling. It asks for 5/8" TYPE X on the garage CEILING where habitable space sits above. So a detached-ceiling garage wall is a 1/2" job and a bonus room over the garage is a 5/8" Type X job. Check the actual assembly against the code table rather than reaching for 5/8 everywhere or 1/2 everywhere.

1/4" flexible: curves; lining.

Moisture-resistant (green board): bath + kitchen wet zones; behind tile.

Cement board (Durock, Hardibacker): tile substrate in wet area (shower, tub).

Mold-resistant (purple board): high-moisture areas; mold inhibitor in paper face.

Sheet sizes: 4 × 8, 4 × 9, 4 × 10, 4 × 12 (industry-standard).

Insulation

Fiberglass batt: pink (Owens Corning) OR yellow (Johns Manville); R-13 to R-30 typical; cheap; itchy + skin irritant.

Mineral wool (Roxul, Rockwool): better fire resistance; some sound dampening; itchy.

Cellulose: recycled paper; blown OR dense-pack; mold-treated.

Spray foam (open + closed cell): blown polyurethane; air seal + insulation in one; expensive.

Rigid foam: foundation + sheathing. Polyiso R-5.8 to R-7 per inch (foil-faced, de-rates in cold); XPS R-4.5 to R-5 per inch (pink or blue); EPS R-3.6 to R-4.4 per inch (white beadboard).

Sheep's wool: natural; expensive; specialty.

Vapor barrier / vapor retarder: poly sheeting OR kraft-faced batt; varies by climate.

Roofing materials

Asphalt shingle (3-tab + architectural): most common residential.

Wood shake / shingle: cedar; high-end + traditional.

Tile (clay, concrete): heavy; needs reinforced framing; Southwest + Spanish.

Slate: premium; very long life; very heavy.

Metal (standing seam, corrugated): durable; rising popularity.

Modified bitumen / TPO / EPDM: flat OR low-slope roof.

Underlayment: felt OR synthetic; under shingles.

Ice + water shield: bituminous membrane at eaves OR valley.

Siding

Vinyl: most common residential; low cost.

Fiber cement (Hardie): durable; paint-receptive; rising popularity.

Wood (cedar lap, T1-11 plywood): traditional; high maintenance.

Stucco: 3-coat OR EIFS (synthetic).

Brick veneer: structural OR decorative.

Stone: high-end.

Aluminum: older; some commercial.

Concrete + masonry

Concrete mix: portland cement + aggregate + water; cures in 28 days to full strength.

Mortar: cement + lime + sand; for laying brick OR block.

Grout: thinner mortar; for filling joints (tile + masonry).

Concrete block (CMU - 8x8x16): foundations, retaining walls.

Brick: standard 4 × 8 × 2.25 ", varieties.

Stone: cut OR rubble.

Rebar: reinforcing steel for concrete; #4 (1/2"), #5 (5/8"), #6 (3/4") common residential.

Common service-trade interactions

HVAC: framing 2×6 walls allow R-19 batt + ducted insulation; basement / crawl space conditioned space affects calculations.

Plumbing: 2×4 walls (interior) tight for vent stacks; 2×6 walls (exterior) accommodate larger DWV better.

Electrical: drilling through studs (NEC 300.4 protections); not drilling through joists weakening structure.

Roofing: identifying decking material under shingles (plywood OR OSB; condition affects warranty).

Painting: drywall (latex; primer for new); wood (oil OR latex; primer for stain blockage).

Common building material mistakes

Drilling through structural OR notching beyond NEC / IRC limits (weakens). Mistaking OSB for plywood (both perform similarly for sheathing; differ for outdoor exposure). Mixing PT with regular fasteners (corrosion within 1 yr; HDG OR stainless required). Using regular drywall where Type X required (code violation). Skipping vapor barrier in cold climates. Insulation in wrong orientation (kraft face wrong side).

Truck stock (general repair work)

Drywall screws (1-1/4", 2"), drywall tape + mud (1 qt joint compound), assorted lumber scraps (2×4 scraps), screws + nails assortment, caulk (latex + silicone), insulation roll (1 batt), poly sheeting roll.

Identifying old materials (potential hazards)

Asbestos: insulation around old pipes (white covering), some floor tile (9×9), some siding (transite), older drywall mud + tape. PRE-1980 = test before disturbing.

Lead paint: pre-1978 homes. Test before sanding OR disturbing.

PCBs (polychlorinated biphenyls): old fluorescent ballasts, transformer oil, caulk.

Knob + tube wiring: pre-1940; insurance + code issues.

Code requirements

Fire separation: garage-to-dwelling separation per the IRC table, 1/2" gypsum on the garage side of the wall, 5/8" Type X on a garage ceiling under habitable space. This is IRC, not NEC.

Emergency escape and rescue openings: required in basements and in every sleeping room, per IRC R310. The code sets a MAXIMUM sill height above the floor and MINIMUM clear opening dimensions, so read each limit in the direction the code states it.

Insulation R-values: per climate zone (IECC).

Stair specifications: tread + riser limits (IRC R311).

Handrail + guardrail: per IRC.

Customer-visible materials education

Customers judge the repair by what they can see. Explain the material before you install it and the questions never come.

"That 2x4 isn't 2 inches by 4 inches." Nominal versus actual. Lumber is named at rough-sawn size and sold at dried, planed size. Nothing is wrong with the board.

"Why doesn't the new siding / shingle / trim match?" Everything on the exterior has faded since it went on, and dye lots vary. A patch will always read slightly different until it weathers, which takes a season or more. If a visual match matters, the answer is replacing a full plane or elevation, not a patch, and that is a different price.

"The patch is going to show." Drywall repair is compound and tape over a joint. It is flat and invisible only after prime and paint, and only if the surrounding paint is close. Say this before you start, not after they see it.

"Why is the new wood green and wet?" Pressure-treated lumber ships saturated with preservative. It is heavy, it will shrink and check as it dries, and it needs hot-dipped galvanized or stainless fasteners. Ordinary screws corrode out of it inside a year.

"OSB is cheap junk." For sheathing and subfloor it performs to the same structural rating as plywood. It swells at cut edges when it stays wet, so it goes where it stays dry. Plywood earns its premium in exposed and wet locations.

"Why does that wall need the thicker drywall?" Fire-rated assemblies, garage-to-house separation in particular, are code, not upsell. Same for the insulation R-value in the climate zone.

On pre-1980 homes, when you expose old pipe wrap, floor tile, or joint compound, do not speculate. Tell the customer it is the age range where asbestos is possible, stop disturbing it, and explain that testing comes before removal. The same caution applies to painted surfaces in pre-1978 homes.

References

• IRC Chapter 5 + 6 (wood frame construction)
• AWPA U1 (treated wood standards)
• ASTM C1396 (gypsum board; supersedes the older C36 specification)
• APA (Engineered Wood Association)
• Manuall internal: Common Codes Overview, PPE Selection