Permits

Most Lower Mainland municipalities require a building permit for a deck above a certain height, and some require one regardless of height. Setback rules from property lines, lot coverage limits, and guard and stair requirements also apply. Because thresholds differ between Langley Township, Surrey, and Abbotsford, confirm with your city before building rather than after.

Guards and stairs are the most commonly cited items: guard height, maximum gap between balusters, stair riser consistency, and handrail graspability are all specified in code.

The connection to the house

This is the single most important detail in a deck, and the most common serious failure. Where a deck ledger attaches to the house, two things have to be right:

  • Structural attachment. Correct fasteners into structure, at the correct spacing. Not nails into sheathing.
  • Flashing. Properly installed flashing that directs water out and away rather than into the wall assembly behind the ledger.

A ledger without adequate flashing traps water against the rim joist and sheathing. In a wet climate that leads to rot in the structure holding the deck up, and the damage is hidden until it's serious. Freestanding decks avoid this entirely by not attaching to the house, which is sometimes the better approach.

In coastal BC, assume everything stays wet. Design so water drains and air moves. Anything that traps moisture against wood will eventually rot, regardless of how good the material is.

Details that decide lifespan

  • Ground contact and footings. Posts on properly sized footings below frost depth, not sitting on soil, with post bases that keep end grain off concrete.
  • Drainage and gaps. Spacing between boards so water passes and debris doesn't pack in. Blocked gaps hold moisture against joists.
  • Joist protection. Joist tape over the top of joists sheds water away from the fastener holes where rot typically starts.
  • Correct fasteners. Hardware and screws rated for exterior use and compatible with treated lumber, which is corrosive to the wrong metals.
  • Ventilation underneath. Airflow under the deck matters as much as what's on top.
  • Clearance from siding, so the deck surface doesn't wick water into cladding.

Material choices, honestly

Pressure treated lumber is the most economical and performs well when detailed and maintained, though it needs periodic cleaning and re-coating. Cedar looks better and is naturally more rot resistant, at a higher cost. Composite eliminates re-staining and is dimensionally stable, but the substructure underneath is still wood and still needs correct detailing and drainage. No decking material saves a deck built on a bad frame.

Maintenance that actually extends life

  • Clear debris from between boards, especially in fall
  • Keep gutters and downspouts from discharging onto the deck
  • Trim vegetation back so the structure dries out
  • Check the ledger and posts annually for soft spots or staining
  • Re-coat wood decks on the schedule the product calls for, not when it looks bad

Common questions

Do I need a permit to build a deck in BC?

Most Lower Mainland municipalities require a building permit for decks above a certain height, and some require one regardless of height. Setbacks, lot coverage, and guard and stair requirements also apply, and thresholds vary between cities, so confirm with your municipality before building.

What is the most common cause of deck failure?

The connection where the deck ledger attaches to the house. Inadequate flashing traps water against the rim joist and sheathing, causing hidden rot in the structure supporting the deck. A freestanding deck avoids this by not attaching to the house.

Is composite decking better than wood?

Composite avoids re-staining and is dimensionally stable, but the substructure beneath it is still wood and still requires correct fasteners, flashing, drainage, and ventilation. Decking material does not compensate for a poorly built frame.

This guide is general information for Metro Vancouver and the Fraser Valley, not legal advice or a substitute for your municipality's building department. Requirements vary by city and by project.