Louisiana Residential Construction

Key Concepts

Soil & bearing capacity - Presumptive load-bearing values (IRC Table R401.4.1): crystalline bedrock 12,000 psf; sedimentary and foliated rock 4,000 psf; sandy gravel and/or gravel (GW, GP) 3,000 psf; sand/silty sand 2,000 psf. - If a building official thinks soil bearing capacity may be less than 1,500 lbs./sq. ft., a soil test may be required (Carpentry and Building Construction, Sec. 10.1). - Footings must always rest on undisturbed soil. If the site has been dug too deep, it must be filled with concrete, never soil (Carpentry, p. 256).

Site layout - The plot plan shows building location; marking it on the land is the site layout (Carpentry, Ch. 9). - An existing street or marked property line can serve as a reference line, allowing stake-out without a surveying instrument (Carpentry, Ch. 9 — Measuring From a Reference Line). - A theodolite is a transit that reads horizontal and vertical angles electronically, needs no vernier scale, and displays readings on an LCD screen (Ch. 9 — Types of Instruments). - Leveling a transit…

Key Concepts

Mixture components - Concrete requires all four ingredients — cement, water, fine aggregate, coarse aggregate. Omit the coarse aggregate and the material is mortar or grout (Carpentry & Building Construction, Ch. 8 — Concrete Ingredients). - Hydration is the chemical reaction between water and cement; it generates heat and hardens the concrete. Concrete does not "dry out" (Ch. 8 — Hydration). - In manufacturing Portland cement, no more than 5 percent gypsum is added to the clinker before grinding (Ch. 8 — Portland Cement). - Type III (high-strength/high-early-strength) is used where forms must be stripped or the concrete put in service quickly; it reaches in 7 days about the strength Type I reaches in 28 days (Table 8-1; Contractor's Guide, pp. 14-15). Type IV (low heat) is for massive structures such as dams (Table 8-1; Modern Masonry, Ch. 18, p. 383). - Self-leveling cement flows like thin syrup and is used in remodeling to level uneven subfloors (Ch. 8 — Specialty Cements). - Five-bag mix (five bags of cement per cubic yard)…

Key Concepts

Foundation walls and veneer support - Concrete and masonry foundation walls shall extend above the finished grade a minimum of 4 inches where masonry veneer is used and a minimum of 6 inches elsewhere (IRC R404.1.1.6; Modern Masonry, p. 313). - The foundation brick ledge supporting brick veneer should be at least equal to the total thickness of the brick veneer wall assembly (Modern Masonry, p. 333, Sec. 16.1.5). - Below grade, the foundation wall receives ½" cement parging covered with bituminous waterproofing (Modern Masonry, p. 334, Sec. 16.1.5, Fig. 16-13). - Masonry systems shall have a minimum specified compressive strength of 1,500 psi (IRC R402.4, p. 90). - Mortar for plain masonry foundation walls shall be Type M or S, laid in running bond (IRC Table R404.1.1(1), footnote a, p. 112). - Footings for masonry fireplaces and chimneys shall extend not less than 6 inches beyond the face of the fireplace or foundation wall on all sides (IRC R1001.2, p. 447).

Key Concepts

Wall framing — IRC Chapter 6 - Sawn lumber for load-supporting purposes must be identified by a grade mark of an accredited lumber grading or inspection agency and have design values certified by an accreditation body complying with DOC PS 20 (R602.1.1). - Wood structural panel sheathing must conform to DOC PS 1, DOC PS 2, or, if manufactured in Canada, CSA O325 or CSA O437; panels are identified for grade, bond classification, and performance category (R602.1.8). - End joints in top plates must be offset not less than 24 inches; joints need not occur over studs (R602.3.2). - Where joists, trusses or rafters are spaced more than 16 inches o.c. and bearing studs below are spaced 24 inches o.c., the members must bear within 5 inches of the studs beneath. Exceptions: two 2x6 or two 3x4 top plates, a third top plate, or solid blocking equal in size to the studs (R602.3.3). - Interior nonbearing walls may be built with 2-inch by 3-inch studs spaced 24 inches o.c. (R602.5). - Notching:…

Key Concepts

Drywall types and sizes - Standard sheets are commonly 4' wide and 8' long; panels also come in 9', 10', 12', and 14' lengths. The most common thickness is 1/2" (Carpentry and Building Construction, Ch. 32, Standard Drywall). - Edges along the length of a panel are tapered so joints can be filled with compound and smoothed flush with the surface (Ch. 32, Standard Drywall). - Type-X fire-code drywall is 5/8" thick and contains glass fibers that keep it from crumbling in extreme heat. Type-C is even more fire resistant and contains vermiculite (Ch. 32, Fire-Code Drywall). - Glass-mat gypsum board ("paperless drywall") has front and back faces covered by thin fiberglass instead of paper and is approved for shower stalls and tub/shower surrounds; green board is no longer allowed there (except ceiling surfaces) (Ch. 32, Moisture-Resistant Drywall). - Specialty products: foil-back (foil serves as a vapor retarder), flexible drywall (double-layer for curved walls), and sound-resistant drywall containing sound-absorbing polymers (Ch. 32, Specialty Drywall).

Key Concepts

Roof slope categories and minimums - Three basic slope categories: Flat (below 2½-in-12), Low slope (2¼-in-12 to 4-in-12), High slope (4-in-12 or greater). Most shingled roofs are high-slope. (Carpentry and Building Construction, Section 22.1 — Roof Slope) - Strip shingles are installed on roofs with a slope of 4-in-12 or greater; lower slopes require consulting the manufacturer's literature. (Section 22.2 — Installation Issues) - Code minimum slope for asphalt shingles: 2:12. From 2:12 up to 4:12, double underlayment is required. (IRC R905.2.2) - Clay and concrete tile: 2½:12 or greater. (IRC R905.3.2)

Sheathing and decking - Asphalt shingles shall be fastened to solidly sheathed decks. (IRC R905.2.1) - Wood shingles may be installed on solid or spaced sheathing; spaced sheathing boards not less than 1-inch by 4-inch nominal, spaced on centers equal to the weather exposure. (IRC R905.7.1) - OSB roof sheathing: minimum 7/16 inch (nominal). (Roofing Construction and Estimating, Ch. 2) - NRCA does not recommend installing roof systems over structural wood panel decks less than nominal **1/2 inch (actual 15/32…

Estimating, Plan Reading and General Code Requirements

Key Concepts

IRC Scope and Applicability - The IRC applies to detached one- and two-family dwellings and townhouses not more than three stories above grade plane in height with a separate means of egress (IRC Section R101.2). - Where a general requirement conflicts with a specific requirement, the specific requirement governs (IRC Section R102.1).

Permits - A permit application is deemed abandoned 180 days after the date of filing unless pursued in good faith or a permit has been issued (IRC Section R105.3.2). - An issued permit becomes invalid if work is not commenced within 180 days after issuance, or if more than 180 days pass between inspections (IRC Section R105.5). - Permit exemptions (IRC Section R105.2): one-story detached accessory structures with floor area not exceeding 200 square feet; fences not over 7 feet high; retaining walls not over 4 feet. Decks attached and serving an exit door are not exempt.

Key Concepts

Fall protection - Employees in residential construction 6 feet or more above lower levels must be protected by guardrail systems, scaffolding, a safety net system, or a personal fall arrest system — 29 CFR 1926, §1926.501(b)(13); BCSI B11 Fall Protection & Trusses, Page 89. The same 6-foot trigger applies to masonry and "most types of construction activities" (Safety, Section 4.2.6). - Falls are the leading cause of deaths in construction, accounting for approximately 40% of construction fatalities; lack of fall protection is OSHA's most cited construction violation (Safety, Section 4.2.6). - Guardrail top edge height: 42 inches (1.1 m) plus or minus 3 inches (8 cm) above the walking/working level — §1926.502(b)(1) (i.e., a 39–45 inch range). - Guardrail strength: top rail must withstand at least 200 pounds (890 N) applied within 2 inches of the top edge in any outward or downward direction — §1926.502(b)(3). Midrails and intermediate members: 150 pounds — §1926.502(b)(5). - A lifeline must be secured to a structural member above the worker capable of supporting a minimum…