March: post-winter structural assessment
Metro Vancouver's freeze-thaw cycle — temperatures oscillating around 0°C from November through February — works against exterior sealing every winter. Caulk cracks, flashing loosens, weatherstripping compresses permanently, and foam degrades at penetration points. March is the first dry month to properly walk the perimeter and document what winter broke. This assessment is not optional; skipping it means treating symptoms all summer instead of fixing the entry points once.
- Walk the full exterior perimeter at dusk with a flashlight — pest entry points show up as shadows you miss in daylight.
- Inspect every utility penetration: gas, water, cable, dryer vent, A/C condensate line, solar conduit.
- Check soffit-fascia junctions along every roofline — these are the #1 roof rat and carpenter ant entry vector in Vancouver-area craftsman homes.
- Walk the foundation perimeter for cracks, settled grading, or any gap where wood contacts soil.
- Check gable vents and crawlspace vents for damaged screens — mice and rats use these all winter.
- Photograph every gap you find. The photo log becomes the scope of work for April sealing.
April: queen wasp watch + carpenter ant treatment window
Two of BC's most impactful pest interventions share an April window: disrupting queen wasp nest establishment and treating carpenter ant colonies before swarmer flights peak. Missing April on either species means managing larger, more aggressive populations in June and July.
- Watch for solo queen yellowjackets scouting eaves, soffits, and deck joist bays from late March onward. A queen alone — before she has any workers — can be removed without protective gear and without chemicals.
- Check inside shed roofs, BBQ covers, and outdoor cushion storage — common early-season queen staging areas.
- Begin carpenter ant treatment if any indoor activity was observed over winter, or if swarmers emerged last May. Spring treatment gets the colony while foraging tunnels are active and accessible.
- Complete all exterior sealing work identified in the March assessment before April is out — before carpenter ant and wasp activity ramps up.
- Clean gutters and extend downspouts away from the foundation — wet soil against the foundation is a carpenter ant and earwig magnet.
- Schedule the first quarterly subscription visit (if applicable) for late April.
May: full-season preparation
- Address any wasp nest establishment observed in April — early nests are golf-ball to tennis-ball sized and simple to treat.
- Carpenter ant swarmer flights peak in late April through May; see our companion article on [what swarmers mean for your home](/guide/carpenter-ant-swarmer-season-bc).
- Begin exterior perimeter pest applications if applicable — typically covers May through October.
- Trim all tree branches contacting the roofline. Carpenter ants use overhead branches as highways from outdoor colonies to structural wood.
- Clear vegetation within 1 metre of the foundation — dense ground cover retains moisture and harbours earwigs, millipedes, and springtails.
- Inspect attic insulation for rodent nesting or tunnelling from any winter activity — easier to address before summer heat makes attics inaccessible.
| Month | Primary pest risk | Key action |
|---|---|---|
| March | Rodent entry still active; structural gaps from freeze-thaw | Full perimeter inspection; document gaps |
| April | Queen wasp establishment; carpenter ant foraging resumes | Seal all gaps; intercept queen wasps; treat carpenter ants if prior activity |
| May | Carpenter ant swarmers; wasp colony growth; outdoor pest trail establishment | Swarmer diagnosis; address early wasp nests; begin perimeter applications |
Spring moisture checklist — the overlooked driver
BC's spring rainfall drives pest pressure as much as temperature. Saturated soil forces earwigs, millipedes, springtails, and slugs toward dry spaces — which means toward your foundation and entry points. Carpenter ants actively seek moisture-damaged wood. Moisture management in spring is pest management.
- Confirm all downspouts discharge at least 2 metres from the foundation.
- Check for any standing water in crawlspace or basement after rain — should drain within 24 hours.
- Inspect wood framing in crawlspace for any soft spots, staining, or visible fungal growth — these are carpenter ant targets.
- Replace any foam pipe insulation that contacts soil — mice and rats shred it to build nests.
- Ensure exterior irrigation timers have not been reactivated against the foundation — common spring oversight.
Frequently asked questions
How early in spring should I start the checklist?+
Mid-March is the right start in Metro Vancouver, even if nights are still cold. The inspection and planning work can be done in any weather; sealing is best done in dry conditions above 5°C, which is typically reliable from late March onward.
Can I do the spring inspection myself?+
Yes, the inspection is a DIY task — walk the perimeter, use a flashlight, document gaps. The repair work (mesh, flashing, hardware cloth) is also DIY-able for handy homeowners. The carpenter ant and wasp treatment components are where professional application adds meaningful value, because the products and protocols differ from what's available at hardware stores.
Do I need to do this every year?+
Yes. BC's freeze-thaw cycle reopens entry points every winter. A spring inspection is not a one-time fix; it's annual maintenance, the same as cleaning gutters or servicing a furnace. Homes that do this annually average significantly fewer summer pest callouts than homes that don't.