Exterior Assemblies - Studying Against an Unverified Outline
What this section covers
No official blueprint for LICT-Exterior was supplied, so no topic weighting, task list, or reference edition can be quoted with confidence here. Treat every published "Exterior" outline as unverified and plan around the one thing the title reliably implies: exterior envelope assemblies - roofs, walls, cladding, flashing, drainage, and the interfaces between them. Where a number appears in your study material (clearance to grade, lap width, nail spacing), confirm it against the code edition your jurisdiction actually adopts before memorising it.
The controlling principle: weather-lap
Water reaches the envelope by gravity, capillary action, and wind-driven pressure. Every exterior assembly is built on a single rule: each layer sheds onto the layer below it, and each material laps over the one beneath in the direction of flow. Shingle-lap, not reverse-lap. Drainage planes are lapped so water always exits at the bottom edge of the assembly, never behind it.
Control layers are separate jobs
Bulk-water control (cladding, roofing, flashing), drainage (weather-resistive barrier, cavity), air control, vapour control, and thermal control are distinct functions. A vapour retarder is not a waterproof membrane, and a WRB is not a flashing. Most inspection failures and exam distractors come from collapsing two of these into one product.
Worked example
A roof-to-wall intersection: install wall WRB first; set step flashing with each shingle course so the vertical leg runs up the wall and the horizontal leg laps onto the shingle below; lap the WRB over the step-flashing vertical leg; finish with counterflashing let into the wall; add a kick-out flashing at the low end to divert water away from the wall face. Reasoning: every component sheds onto the next lower component, and nothing depends on sealant for waterproofing.
Traps that cost marks
- Substituting sealant or caulk for flashing.
- Reversed laps - WRB or underlayment lapped the wrong way.
- Fasteners driven through the drainage plane below the lap line.
- Calling a vapour retarder "waterproofing".
- Carrying a clearance or lap dimension across code editions without checking.