Why We Wrote This Guide

Before Johnny and I started Dads Roofing in 2021, we spent years working as Red Seal Boilermakers in the oil sands. Boilermaking is unforgiving -- every weld gets X-rayed, every seam gets pressure-tested, and if your work does not meet code, it gets cut out and redone at your expense. That training changed the way we think about every trade we touch, including roofing.

When we transitioned into roofing here in Agassiz, we brought that code-first mindset with us. Over 500 roofs later, we still treat the BC Building Code as our floor, not our ceiling. This guide breaks down every section of the code that touches your roof, written in the plain language we would use standing in your driveway.

The Code That Governs Your Roof: BC Building Code 2018

British Columbia operates under the BC Building Code 2018, which adapts the National Building Code of Canada 2015 with province-specific amendments for our seismic zones, rain loads, and snow accumulation. Your municipality may add further requirements on top of the provincial code -- and in the Fraser Valley, several do.

The key thing to understand: the code sets minimums. A code-compliant roof is a roof that will not get you fined. A good roof exceeds code in the areas where local climate demands it. In the Fraser Valley, those areas are ice protection, ventilation, and fastening.

Fire Ratings: What Your Shingles Must Withstand

Class A, B, and C -- What They Mean

Every roofing material sold in BC carries a fire classification. Class A offers the highest fire resistance, Class C the lowest. The classification is determined by standardized testing that measures how well the material resists flame spread and burning-brand penetration.

Class A materials (highest protection):

• Fiberglass-mat asphalt shingles -- the most common residential choice
• Standing seam and corrugated metal roofing
• Concrete and clay tiles
• Fire-retardant-treated wood shakes (specialty product)

Class B and C materials:

• Some organic-mat shingles (largely phased out)
• Untreated cedar shakes -- typically Class C
• Restricted or prohibited in most Fraser Valley urban zones

Fraser Valley Fire Rating Rules

Every municipality from Hope to Abbotsford requires Class A fire-rated roofing in urban zones and wildfire interface areas. Given that much of the Fraser Valley backs onto forested Crown land, interface zones are common -- Harrison Hot Springs, parts of Agassiz, and the hillside neighborhoods in Chilliwack all fall within these designations. If you are unsure whether your property sits in an interface zone, your local building department can tell you in a quick phone call.

Wind Resistance: Designed for Outflow Events

The Fraser Valley sits in a moderate wind zone under the code, with a 1-in-50-year design wind speed of roughly 80 to 100 km/h. But anyone who has lived through a Fraser Valley outflow event knows that localized gusts can far exceed those numbers. The code requires shingles rated to a minimum of 110 mph (177 km/h), and manufacturer specs often go further.

Standard wind-zone fastening:

• 4 nails per shingle -- the bare code minimum
• Adhesive strip (self-sealing) must be intact and bonding

Enhanced fastening for exposed sites:

• 6 nails per shingle -- required on hilltops, open fields, lake-facing slopes
• Starter strip with adhesive at eave and rake edges

Johnny and I nail six on every roof, regardless of exposure classification. The extra material cost is around $200 to $300 on a typical home, and it means the difference between losing shingles in an outflow event and keeping them. After seeing the damage that November windstorms do across Agassiz and Harrison, we consider six nails the only responsible choice.

Snow Load: The Numbers That Size Your Structure

Snow load is the weight your roof structure must safely carry during peak accumulation. The code assigns design snow loads based on historical weather data for each municipality. These numbers directly affect rafter sizing, truss engineering, and whether your existing deck can handle a re-roof.

Fraser Valley ground snow loads (1-in-50-year):

• Abbotsford: 1.8 kPa -- the lightest in the valley, reflecting its lower elevation
• Chilliwack: 2.0 kPa
• Agassiz / Harrison: approximately 2.2 kPa (higher due to lake-effect precipitation)
• Hope: 2.4 kPa -- the heaviest in the valley floor
• Elevated properties: can reach 4.0 kPa or higher depending on altitude

When we inspect a roof for replacement, we always check whether the existing structure was designed for the current code snow load. Older homes -- especially pre-1990 builds -- sometimes have undersized rafters that were acceptable under earlier codes but do not meet 2018 standards. In those cases, we flag the structural concern before quoting the roofing work.

Ventilation: The 1:300 Rule and Why the Valley Demands More

Code Minimums

The BC Building Code requires a net free ventilation area of at least 1 square foot for every 300 square feet of insulated ceiling (the 1:300 rule). That ventilation must be balanced: approximately 50% at the soffit for intake and 50% at the ridge or upper gable for exhaust.

Worked example: A 1,500 sq ft attic floor needs at least 5 sq ft of total vent area -- 2.5 sq ft at the soffits and 2.5 sq ft at the ridge.

Acceptable Ventilation Configurations

• Ridge vent + continuous soffit vents: The gold standard. Provides uniform airflow across the entire deck.
• Gable vents + soffit vents: Acceptable for simpler roof shapes. Less effective on complex hip roofs.
• Individual roof vents (pot vents) + soffit vents: Functional but requires enough units spaced correctly.
• Powered attic ventilators: Code-permitted but problematic. They can depressurize the attic and pull conditioned air through ceiling leaks, increasing energy costs.

Why Ventilation Is Critical in the Fraser Valley

Our climate is wet and mild for much of the year, which creates conditions where condensation thrives. In winter, warm moist air from the living space migrates into the attic through ceiling penetrations. Without adequate exhaust, that moisture condenses on the underside of the roof deck, leading to mold growth, OSB delamination, and rot. In summer, a poorly ventilated attic can hit 70 degrees Celsius, cooking shingles from below and cutting their lifespan by years.

On every tear-off, Johnny and I assess the existing ventilation and bring it to code -- or above -- before the new shingles go on. It is one of the most impactful upgrades we can make during a re-roof.

Underlayment: Your Second Line of Defense

Code Minimums

• #15 asphalt-saturated felt: Still code-legal, but we do not use it. It tears easily during installation, wrinkles under heat, and degrades faster than synthetic alternatives.
• Synthetic underlayment: Exceeds code, lighter, stronger, and lies flat on the deck. This is what we install on every project.
• Coverage: Entire roof deck must be covered before shingles are installed.

Ice and Water Shield -- Where Code Falls Short

Code minimum:

• 36 inches (900 mm) of self-adhering membrane from the eave edge
• Required in all valleys -- 36 inches to each side of the valley centerline
• Required around all penetrations: chimneys, skylights, vent pipes

What we install (and why):

• 72 inches (6 feet) from every eave edge. Fraser Valley freeze-thaw cycles create ice dams that regularly extend 4 to 6 feet up the roof. The code minimum leaves the upper half of that dam zone unprotected.
• Full-length valley coverage. Valleys concentrate the largest water volume on any roof. Partial coverage is a gamble we do not take.
• Generous wraps around all penetrations. Chimneys, skylights, and plumbing stacks are where most leaks originate. Extra membrane here costs pennies and prevents thousands in damage.

Flashing: The Details That Make or Break a Roof

Valley Flashing

• Material: Corrosion-resistant metal -- galvanized steel, aluminum, or copper
• Minimum width: 24 inches (610 mm)
• Underlayment: Ice and water shield required beneath the metal

Step Flashing at Wall Intersections

• Size: Minimum 5-inch by 5-inch (125 mm x 125 mm) L-shaped pieces
• Installation: One piece woven into each shingle course, lapping over the piece below
• Counter-flashing: Required over the top of the step flashing to shed water away from the wall

Caulk is not flashing. We see this shortcut constantly on re-roofs -- someone runs a bead of sealant where step flashing should be, and within a year or two, water is running down the inside of the wall. Proper metal step flashing, installed one piece per course with counter-flashing over top, is the only method that meets code and actually works long-term.

Chimney Flashing

• Base flashing: Metal apron at the chimney base, turning up the chimney face
• Counter-flashing: Reglet-cut into the mortar joint or mechanically fastened, lapping over the base flashing
• Cricket (saddle): Required for any chimney wider than 30 inches on the upslope side. The cricket diverts water around the chimney instead of pooling behind it.

Fastening: Why Nail Placement Matters as Much as Nail Count

Shingle Nailing

• Code minimum: 4 galvanized roofing nails per shingle, minimum 1-1/4 inch length
• High-wind zones: 6 nails per shingle
• Placement: In the manufacturer-designated nailing zone, which sits just above the adhesive strip. Nails placed too high miss the underlying shingle and reduce wind resistance dramatically.

Nail placement is something homeowners rarely think about, but it is one of the most common causes of wind damage. A shingle nailed an inch too high is effectively unnailed -- the adhesive strip never seals, and the first strong gust lifts it. This is something Johnny watches like a hawk on every crew we run.

Roof Deck Fastening

• Minimum sheathing thickness: 3/8 inch for residential (most homes use 1/2 inch or 5/8 inch)
• Fastener: 8d common nails or equivalent ring-shank screws
• Edge spacing: 6 inches on center along all panel edges
• Field spacing: 12 inches on center at intermediate supports
• Expansion gap: 1/8 inch between sheets to accommodate moisture swelling

Energy Code: Insulation and the Step Code

The BC Energy Step Code is a performance-based framework that municipalities can voluntarily adopt. While not all Fraser Valley municipalities have fully adopted it, the direction is toward higher energy standards with each code cycle.

• Attic insulation minimum: R-40 for Climate Zone 4, which covers the entire Fraser Valley
• Typical installation: 12 to 14 inches of blown fiberglass or cellulose
• Critical detail: Insulation must not block soffit vents. Proper baffles at each rafter bay maintain the airflow path from soffit to ridge.

During a tear-off, we always check the attic insulation depth and baffle situation. If baffles are missing or crushed, we replace them before the new roof goes on. It is one of those small interventions that prevents major problems down the line.

Permits: When You Need One and What It Costs

Full Roof Replacement

Every municipality in the Fraser Valley requires a building permit for a full roof replacement. The permit ensures the work will be inspected for code compliance -- typically a sheathing inspection before underlayment goes on, and sometimes a final inspection.

• Cost: $100 to $300 depending on the municipality and scope
• Timeline: Usually issued within a few business days
• Who pulls it: The contractor. At Dads Roofing, we handle the permit for every full replacement.

Repairs

• Minor repairs (replacing a few shingles, re-sealing a vent boot): No permit required in most cases
• Major repairs (re-decking a section, structural modifications): Permit typically required
• When in doubt: A quick call to your municipal building department will clarify

Municipality-by-Municipality

Kent (Agassiz) / Harrison Hot Springs:

• Permit required for full replacement -- District of Kent Building Department
• Additional considerations in lakeshore and flood plain zones

Chilliwack:

• Permit required. Online application available through the City of Chilliwack portal.
• Wildfire interface zones apply in hillside neighborhoods -- Class A mandatory

Abbotsford:

• Permit required. Energy Step Code compliance may apply to new construction or major renovations.

Hope:

• Permit required. Contact the District of Hope Building Department.
• Higher snow loads (2.4 kPa) may trigger structural review on older homes

Code Violations We Encounter on Tear-Offs

After stripping over 500 roofs across the Fraser Valley, Johnny and I have developed a mental catalog of the shortcuts that come back to haunt homeowners. Here are the four we see most often:

1. Minimal ice and water shield at the eaves

The previous roofer installed the code-minimum 36 inches, and ice dams drove water past it by the second winter. We see the water staining on the deck sheathing every time. The fix: 72 inches of membrane, installed before the first shingle goes on.

2. Blocked or missing ventilation

Soffit vents painted shut. Insulation stuffed against the deck with no baffles. Ridge vent installed but the sheathing beneath it never cut open. All of these produce the same result: a hot, damp attic that destroys shingles from below and grows mold on the deck. The fix: verify every intake and exhaust path is clear and meets the 1:300 ratio.

3. High nailing

Nails placed above the manufacturer's designated zone, missing the underlying shingle entirely. The adhesive strip never bonds, and the shingle is held by friction alone. The first outflow wind peels them off in sheets. The fix: train every crew member on the nailing diagram for the specific product being installed.

4. Caulk instead of step flashing

A bead of roofing sealant where metal step flashing should be. It seals for a season, then cracks, and water runs down inside the wall for years before anyone notices. The fix: individual metal step flashing pieces woven into each course, with proper counter-flashing above.

Code vs. Manufacturer Specs: Which Governs?

This trips up a lot of homeowners, so here is the straightforward answer: follow whichever is stricter. The BC Building Code sets the legal floor. Manufacturer installation specs set the warranty floor. If the manufacturer requires 6 nails and the code says 4, you install 6 -- otherwise your warranty is void even though you technically met code.

In practice, manufacturer specs almost always meet or exceed code. The conflict usually runs the other direction: a contractor who installs to code minimum may be violating manufacturer specs without realizing it. At Dads Roofing, we keep current installation manuals for every product we carry, and we follow them to the letter.

Our Standard: Code as Floor, Not Ceiling

Johnny and I came from a trade where "meeting code" was the absolute minimum expected of a journeyman. The work that earned respect -- and kept people safe -- was the work that exceeded the standard where conditions demanded it.

In the Fraser Valley, conditions demand it in several specific places. That is why every Dads Roofing installation includes:

• 72-inch ice and water shield at every eave (code requires 36)
• 6-nail fastening protocol on every shingle (code allows 4)
• Synthetic underlayment across the full deck (code still permits felt)
• Verified 1:300 ventilation with clear intake and exhaust paths
• Manufacturer-spec flashing at every wall, chimney, and penetration
• Pulled permits and passed inspections on every full replacement

The cost difference between code-minimum and our standard is modest. The durability difference is measured in decades.

Questions about building code requirements for your roof? Kory and Johnny are happy to walk you through it. (778) 539-6917