Material Types
Understanding different construction materials and their measurement units for accurate estimation.
- Concrete Measured in cubic yards. Standard mix ratios: 1:2:4 (cement:sand:aggregate). Typical density: 150 lbs/ft³. Consider slump requirements (2-4" residential, 4-6" commercial).
- Steel Measured in linear feet or weight (tons). Rebar grades: 40, 60, 75 ksi. Common sizes: #3 (⅜") to #18 (2¼"). Allow for overlaps (40x bar diameter) and chairs (2.5 lbs/yd²).
- Lumber Measured in board feet (1 BF = 1"×12"×12"). Typical grades: Select, #1, #2. Account for moisture content (MC 19% max for structural). Species affect strength (Douglas Fir vs Southern Pine).
- Masonry Individual units (bricks: 7⅝"×3⅝"×2¼"). Coverage: 6.75 bricks/ft² with ⅜" mortar. Mortar mix ratio: 1:3 (cement:sand). Include ties (1 per 2.67 ft²).
- Aggregate Measured in tons or cubic yards. Types: coarse (¾"-1½"), fine (sand). Bulk density: 100-120 lbs/ft³. Consider gradation requirements and void ratio (35-45%).
Waste Factors
Cutting Waste
Material loss from sizing:
- Lumber: 7-15%
- Tile: 10-15%
- Drywall: 10-12%
- Rebar: 5-10%
Breakage & Damage
Storage and handling losses:
- Bricks: 5-7%
- Concrete: 3-5%
- Glass: 8-10%
- Insulation: 2-3%
Construction Methods
Process-related waste:
- Formwork: 10%
- Concrete pump: 2-3%
- Mortar mixing: 5-8%
- Welding: 3-5%
Safety Stock
Additional buffer:
- Critical path: 10-15%
- Standard items: 5-10%
- Special order: 2-5%
- Long lead: 3-7%
Cost Factors
- Material Cost Breakdown Base material (60-70%), Transportation (10-15%), Storage (5-10%), Waste (10-15%). Volume discounts typically start at 20+ units.
- Labor Considerations Installation rates: Concrete (0.5-1 cy/hr), Masonry (100-150 blocks/day), Framing (0.5-1 wall/day). Productivity factors: weather (±15%), site access (±10%).
- Equipment Impact Rental vs. Purchase breakeven: 60-70% usage. Operating costs: 15-25% of equipment value annually. Maintenance: 8-12% of purchase price.
- Market Variables Seasonal price fluctuation: ±20%. Regional variations: transport zones add 5-15%. Bulk purchase savings: 10-30% for full loads.