Building Envelope: The Rules the Exam Asks For

Anchoring to concrete follows ACI 318 as supplemented by Section 1905 of the Building Code. The rule covers cast-in headed bolts, headed studs, and hooked J- or L-bolts, and post-installed expansion, undercut, screw, and adhesive anchors.

Building Code § 1901.3

An isolation joint is a full-depth separation, with a compressible filler strip, between a slab on grade and fixed parts of the building such as columns, walls, and footings; it lets the slab shrink, curl, and move without binding on the fixed element and cracking.

Standard trade practice

A control joint, also called a contraction joint, is a weakened plane tooled or saw-cut partway into a slab at regular spacing so that shrinkage cracking opens along that straight line instead of at random.

Standard trade practice

Adding water to a ready-mix load beyond the amount in the mix design raises the water-cement ratio without adding cement, so the cured concrete has lower compressive strength and is more porous than the mix was designed to be.

Standard trade practice

On a hot, dry day a dry, absorbent base is wetted ahead of the truck so it is moist but has no standing water, because a dry base pulls mix water out of the bottom of fresh concrete, weakening that surface and inviting early cracking.

Standard trade practice

Where shallow foundations bear on compacted fill more than 12 inches deep, a geotechnical investigation is required. It must specify site preparation, the fill material, the test methods for maximum dry density and optimum moisture, the maximum lift thickness, the field test for in-place dry density, the minimum acceptable in-place dry density as a percentage of that maximum, and the number and frequency of field tests.

Building Code § 1803.5.8

Lots are graded to drain surface water away from foundation walls. The grade must fall at least 6 inches within the first 10 feet. Where lot lines, walls, slopes, or other barriers prevent that, drains or swales must carry water away from the structure. Impervious surfaces within 10 feet of the foundation slope at least 2 percent away from the building.

Residential Code § r401.3

Before opening an excavation, the excavator determines the approximate location of subsurface installations such as sewer, telephone, fuel, electric, and water lines. Excavation may not begin until the excavator has marked the excavation area as Government Code 4216.2 requires and has received a positive response from every known owner or operator of subsurface installations within the project, confirming their lines are located or that they have none in the way. The regional notification centers for the area, and any known owners of subsurface facilities that are not members of a center, are advised at least two working days before digging starts, except for emergency repair work.

Code of Regulations, Title 8 (Construction Safety Orders) § 1541 ↗

A line of levels run through several instrument setups is continued back to the starting benchmark and the closing elevation is compared with the benchmark's known value; the difference is the error in the run, and a run that does not close within tolerance is rerun before anything is built to its stakes.

Standard trade practice

A ventilated crawl space needs ventilation openings with a net area of at least 1 square foot for each 150 square feet of under-floor area, with one opening within 3 feet of each outside corner, covered by material with openings no larger than 1/4 inch.

Residential Code § r408

Where the ground is covered with an approved Class I vapor retarder, the opening area may drop to 1/1,500 of the under-floor area, and the corner-opening rule no longer applies provided the openings are placed to give cross ventilation of the space.

Residential Code § r408

An unvented crawl space covers the exposed earth with a continuous Class I vapor retarder, joints lapped 6 inches and sealed or taped, edges run at least 6 inches up the stem wall and attached and sealed to the stem wall or to the insulation. It then needs either continuous mechanical exhaust at 1 cubic foot per minute per 50 square feet of crawl-space floor with an air pathway to the common area (a duct or transfer grille), or one of the other listed conditioning options.

Residential Code § r408

Where eave or cornice vents are installed, blocking, bridging, and insulation may not block the free flow of air. At least a 1-inch space is provided between the insulation and the roof sheathing, and at the location of the vent.

Residential Code § r806.3

A U-factor is the overall coefficient of thermal transmittance of a fenestration, wall, floor, roof, or ceiling component, in Btu per hour per square foot per degree Fahrenheit, including the air-film resistance at both surfaces.

Energy Code § 100.1

The Energy Code's Joint Appendix JA4 carries the U-factor, C-factor, and thermal-mass data that must be used for all residential and nonresidential prescriptive compliance calculations. Energy Commission-approved compliance software may adjust the printed values, only by the appendix's own procedures and within its limits, and never when the tables are used manually.

Energy Code § ja4

Where an assembly is not adequately represented in the JA4 tables, the permit applicant or the product's manufacturer may ask the Energy Commission to approve an alternative U-factor for it. The Executive Director grants that approval after reviewing the submittal and supporting information on their merits; acceptable calculation methods are ASHRAE-based, such as hot-box, hot-plate, or heat-flow-meter testing, series/parallel-path calculation for wood framing, and the modified zone method for metal framing. An approved component is published as an addendum to the appendix.

Energy Code § ja4

The JA4 tables are organized by roofs, walls, and floors, then by construction type, with a letter-and-number coordinate naming each value.

Energy Code § ja4

R-value describes insulation effectiveness, but it does not describe the overall performance of a complete assembly; an assembly usually has several layers, each with its own conductance, and the U-factor describes the conductance of every component together.

Energy Code § ja4

Prescriptive compliance is shown either when the insulation's R-value equals or exceeds the R-value required for that envelope feature in the building's climate zone, or when the assembly's overall U-factor is equal to or less than the U-factor required for it.

Energy Code § ja4

For components within wood-framed assemblies that are not represented in the tables, the appendix's example procedure substitutes the different component, such as another insulation R-value, into its worked calculation (a 2x4 wall framed 16 inches on center), which sums the R-values layer by layer through the cavity path (Rc) and the frame path (Rf) and combines them as [1/Rc × (1 − frame%/100)] + [1/Rf × (frame%/100)], with the framing percentage from Table 4.1.6: for conventionally framed walls, 25 percent at 16 inches on center and 22 percent at 24 inches (advanced wall systems 17 percent at 24 inches and 4 percent at 48); floors and roofs 10 percent at 16 inches and 7 percent at 24.

Energy Code § ja4

The Commission's assembly calculator in the compliance software is available for wood, metal, and more advanced assemblies, and its output is usable in a permit submittal; mass-type construction must use approved software.

Energy Code § ja4

For continuous roof insulation tapered for drainage, the prescriptive R-value approach finds the U-factor at the minimum and maximum insulation thickness, averages those two U-factors, and takes the R-value as the inverse of that average. R-values themselves may not be averaged, and the alternative of dividing the roof into sub-areas by insulation thickness is allowed only under the performance method. Adjustments to the appendix's published data are a software matter and are not made when the tables are used manually; an assembly type the tables do not adequately represent takes the approval route.

Energy Code § ja4

Many JA4 tables carry columns for levels of continuous insulation, which is insulation uninterrupted by framing that forms a continuous insulating layer. When a table is used manually, the proposed continuous insulation's rated R-value must be equal to or greater than the R-value shown in the column heading, and no interpolation between columns is permitted. Only Energy Commission-approved compliance software may account for an in-between amount of continuous insulation, using the appendix's Equation 4-1, and that adjustment may not be used for continuous insulation of less than R-2.

Energy Code § ja4

A newly constructed single-family residential building meets the Energy Code by satisfying Sections 110.0 through 110.10, the mandatory features of Section 150.0, and either the performance standards or the prescriptive standards for its climate zone. Additions and alterations use the modified rules in Section 150.2.

Energy Code § 150.1

Under the performance approach the building complies if its calculated energy consumption is no greater than the energy budget of the standard design, computed with Commission-certified compliance software. Efficiency measures may trade against one another inside that budget; the mandatory features still apply.

Energy Code § 150.1

Walls, partitions, and floor-ceiling assemblies separating dwelling units or sleeping units from each other, or from public or service areas, need a sound transmission class of at least 50 when tested per ASTM E90, or a normalized noise isolation class of at least 45 if field tested per ASTM E336. Alternatively, the sound transmission class may be established by engineering analysis, based on a comparison with assemblies whose ratings were determined by ASTM E90 testing, performed by a registered design professional. Penetrations and openings in those assemblies for piping, electrical devices, recessed cabinets, bathtubs, soffits, or heating, ventilating, or exhaust ducts are sealed, lined, insulated, or otherwise treated to keep the rating. That requirement does not apply to entrance doors, which need only fit tight to the frame and sill.

Building Code § 1206.2

Asphalt shingles may be used only on roof slopes of 2 in 12 (17-percent slope) or greater. From 2 in 12 up to 4 in 12 (33-percent slope), double underlayment is required in accordance with Section R905.1.1, whose table draws the line: two layers up to 4 in 12, one layer at 4 in 12 or steeper.

Residential Code § r905.2.2

Under the underlayment table for roof areas where wind design is not required per Figure R301.2.1.1, asphalt-shingle underlayment is one of three options. The first, for slopes from 2 in 12 up to 4 in 12, is two layers: a half-width starter strip at the eave fastened sufficiently to hold in place, then full sheets lapped half a sheet plus 2 inches, end laps 4 inches offset 6 feet. The second, for slopes of 4 in 12 and greater, is one layer applied shingle fashion, lapped 2 inches, with the same 4-inch end laps offset 6 feet; for both, distortions in the underlayment may not interfere with the shingles' ability to seal. The third is a single layer of self-adhering polymer-modified bitumen underlayment complying with ASTM D1970, installed per the underlayment and shingle manufacturers' instructions.

Residential Code § table-r905.1.1-2

Base and cap flashing follow the manufacturer's instructions. Base flashing is corrosion-resistant metal at least 0.019 inch thick or mineral-surfaced roll roofing weighing at least 77 pounds per 100 square feet; cap flashing is corrosion-resistant metal at least 0.019 inch thick.

Residential Code § r905.2.8.1

Valley linings are installed per the manufacturer's instructions before the shingles. An open metal valley needs lining at least 24 inches wide of a corrosion-resistant metal in the code's table. An open valley may instead use two plies of mineral-surfaced roll roofing, an 18-inch bottom layer and a top layer at least 36 inches wide.

Residential Code § r905.2.8.2

A closed valley, covered with shingles, may be lined with one ply of smooth roll roofing complying with ASTM D6380 and at least 36 inches wide, with self-adhering polymer-modified bitumen underlayment complying with ASTM D1970 and at least 36 inches wide, or with any lining permitted for an open valley; valley linings are installed per the manufacturer's instructions before the shingles.

Residential Code § r905.2.8.2

A drip edge goes at the eaves and rake edges of shingle roofs. Adjacent pieces overlap at least 2 inches. The drip edge extends at least 1/4 inch below the sheathing and at least 2 inches back onto the deck, fastened at no more than 12 inches on center. Underlayment goes over the drip edge along the eaves and under it along the rakes.

Residential Code § r905.2.8.5

Built-up roofs have a design slope of at least 1/4 in 12 (2 percent) for drainage, except coal-tar built-up roofs, which may be as low as 1/8 in 12 (1 percent).

Residential Code § r905.9.1

Where roof drains are required, secondary emergency-overflow drains or scuppers are required wherever the roof's perimeter construction extends above the roof so that water would be trapped if the primary drains back up. Their installation and sizing follow Section 1611 and Chapter 11 of the Plumbing Code.

Building Code § 1502.2

Secondary roof drains sit at least 2 inches above the roof surface and no higher than the ponding depth the roof was designed for. They connect one of two ways. A separate piping system, independent of the primary drains, discharges above grade where occupants or maintenance staff can observe it. Or, where the primary storm drainage system connects to building storm water that connects to an underground public storm sewer, the secondary drains may tie into the primary conductor's vertical piping downstream of the last horizontal offset below the roof, with the combined system sized for double the local rainfall rate.

Plumbing Code § 1101.12.2.2

Counterflashing is the separate formed metal let into a chimney's mortar joints above the base flashing and lapped down over the base flashing's upturned edge, so water running down the masonry is shed onto the roof instead of behind the flashing; base flashing turns up against the chimney, counterflashing covers it.

Standard trade practice

Concrete is ordered by the cubic yard, and a cubic yard is 27 cubic feet. For a slab or continuous footing, convert the thickness to feet, multiply length × width × thickness for cubic feet, and divide by 27. Example: a 2-foot-wide, 1-foot-deep footing 120 feet long is 2 × 1 × 120 = 240 cubic feet, or 8.9 cubic yards before waste.

Standard trade practice

A round pier footing is a cylinder: π × radius² × depth in feet gives cubic feet; divide by 27 and multiply by the number of piers. Example: twelve 18-inch piers 3 feet deep have a radius of 0.75 foot; π × 0.75² × 3 = 5.3 cubic feet each, 63.6 total, 2.36 cubic yards.

Standard trade practice

With a builder's level, the height of instrument equals the benchmark elevation plus the backsight reading. The elevation of a point equals the height of instrument minus the foresight reading on it. Backsights are added; foresights are subtracted. Example: benchmark 100.00, backsight 4.25, so the instrument is at 104.25; a foresight of 6.10 puts the stake at 98.15.

Standard trade practice

Slope in percent is the elevation difference divided by the horizontal distance, times 100. Example: elevations 102.50 and 100.00 over 125 feet of run give 2.50 ÷ 125 × 100 = 2 percent.

Standard trade practice

A U-factor is the reciprocal of the assembly's total R-value: U = 1 ÷ R-total, where R-total sums the layer R-values in series, including the inside and outside air films. Example: layers totaling R-20 give U = 0.050.

Standard trade practice

A square of roofing covers 100 square feet of roof surface. Surface area is the plan area times the slope factor, √(rise² + 144) ÷ 12 for a rise-in-12 pitch. Divide by 100 for squares and add waste last. Example: 2,400 square feet of plan area at 6 in 12 has a slope factor of 1.118, so 2,683 square feet, 26.8 squares, and 29.5 squares with 10 percent waste, ordered as 30.

Standard trade practice

For a simple symmetrical gable roof with a centered ridge and the same pitch on both sides, the roof is two equal rectangles: each is the building length times the rafter length, and the rafter length is the run (half the span) times the slope factor. Example: a 40-by-24-foot building at 4 in 12 has a 12-foot run, a slope factor of 1.054, a rafter length of 12.65 feet, and 2 × 40 × 12.65 = 1,012 square feet, about 10.1 squares.

Standard trade practice

Relative compaction is the field dry density of the compacted soil divided by the maximum dry density a laboratory compaction test produced for that same soil, expressed as a percent; a specification such as 90 percent relative compaction is met when the field density reaches 90 percent of that laboratory maximum.

Standard trade practice