Architectural Systems, Materials, and Project Management
Architectural Systems
Envelope
The key idea is four continuous control layers - water, air, vapor and thermal - each must be uninterrupted from foundation to roof. Water control uses drainage planes and a rainscreen with flashings and weeps; vapor goes on the warm side of the insulation in cold climates (reversed in cooling-dominated climates); thermal continuity is broken by balconies, shelf angles and slab edges. Roofs need slope to drains or scuppers, and windows are rated by U-factor (heat flow) and SHGC (solar gain).
Life safety and egress
Classify the occupancy, compute occupant load from code area factors, then size egress. Capacity is 0.2 in per occupant unsprinklered and 0.15 in sprinklered, with a 36 in minimum clear width. Two exits are generally required above 49 occupants or where travel distance is exceeded. Keep exit access, exit and exit discharge distinct. Fire-resistance ratings come from construction type and separation requirements.
Accessibility and acoustics
36 in clear width, 32 in clear door leaf, 60 in turning space, reach 15–48 in, ramps at 1:12 with landings. STC measures airborne sound isolation, IIC impact isolation, NRC absorption - do not swap them.
Traps: confusing travel distance, common path and dead-end limits; applying 0.15 in/occupant to an unsprinklered building; putting the vapor retarder on the wrong side; assuming sprinklers extend every travel limit.
Rule of thumb: exit width = occupants × 0.2 in (unsprinklered) or × 0.15 in (sprinklered), never less than 36 in clear per exit.
Worked example: 300 sprinklered office occupants need 300 × 0.15 = 45 in total; split across two exits that is 22.5 in each, so the 36 in minimum governs each exit.
Materials
Concrete
Strength is specified as 28-day compressive strength (f'c). Water-cement ratio is inversely related to strength and directly related to permeability, so durable exterior concrete wants a low w/c ratio (about 0.45) plus air entrainment for freeze-thaw. Slump measures workability, not strength - a wetter mix is generally weaker. Admixtures accelerate, retard, entrain air or reduce water. Reinforcing steel needs cover for corrosion and fire protection; curing preserves moisture so hydration can continue. ACI 318 governs acceptance testing.
Steel, masonry, wood
Structural steel: A992 for wide-flange shapes, A36 for angles and plates; distinguish yield strength from ultimate (tensile) strength. Connections are bolted or welded, and steel needs fireproofing and often galvanizing. Masonry: CMU with mortar types M, S, N and O in descending compressive strength, grouted and reinforced cores, flashing and weep holes at the base, control joints to manage movement. Wood: species and grade set allowable stresses; moisture content drives shrinkage and checking; preservative treatment is required where decay or termites are a risk; connections usually govern capacity.
Finishes and sustainability
Know how finish systems fail (adhesion, movement, moisture) and how recycled content, VOC limits and durability feed into material selection.
Traps: confusing 7-day with 28-day strength; assuming higher slump means higher strength (it is the opposite); swapping yield and ultimate strength; specifying type M mortar for everything; ignoring wood moisture movement.
Rule of thumb: 7-day strength runs about 70% of 28-day strength; structural concrete in aggressive exposure commonly specified at 4,000–5,000 psi with w/c ≤ 0.45.
Worked example: a specified 4,000 psi mix breaks at 3,600 psi. The single-test floor is f'c − 500 = 3,500 psi, so this test passes that criterion, but the average of three consecutive tests must still equal or exceed 4,000 psi - verify before accepting the placement.
Project Management
Delivery and contracts
Design-bid-build: owner holds separate contracts with architect and contractor, and the architect administers the construction contract fairly. Design-build: one entity holds design and construction. CM at risk: the CM holds the trade contracts and often guarantees a maximum price. CM agency: the CM advises only and holds no trade contracts. Standard AIA documents pair owner-architect (B101) with owner-contractor (A101) and general conditions (A201).
Documents and money
Know the flow: request for information, submittal and shop drawing review, change order (agreed price and time), construction change directive (directed work without agreement on price), architect's supplemental instruction. Cost control uses a schedule of values, monthly pay applications, retainage withheld until completion, contingency for unknowns, and lien waivers as payment conditions.
Time
Critical path method: the critical path is the longest path through the network and has zero total float. Total float = LS − ES = LF − EF. Crashing adds resources to critical activities; fast-tracking overlaps design and construction. Substantial completion means the owner can occupy for its intended use - warranties start, the punch list remains, and retainage is often partly released; final completion comes later.
Traps: assuming a CM agent holds trade contracts; treating float as unlimited; confusing substantial completion with final payment; issuing a change order when price was never agreed (that is a directive); assuming the architect guarantees the contractor's means and methods.
Rule of thumb: total float = late start − early start; the path with zero float is critical and any delay there delays the project day for day.
Worked example: two parallel paths of 12 and 16 days give a 16-day project; the 12-day path carries 4 days of total float before it becomes critical.