You found them where it's quiet and damp: along the baseboard, behind storage bins, in the floor drain area, or tucked into cardboard. Silverfish don't "move in" because your home is dirty. They show up because the basement gives them what they need: humidity, hiding spots, and food they can chew.
Why silverfish keep showing up in basements around London
In older parts of the city—Old North, Wortley Village, pockets of Westmount, even finished basements in Byron—the pattern is the same: basements that swing humid in spring and summer, then cool down fast in fall. Silverfish handle that better than most insects.
The main drivers:
- Humidity above ~50–60% for long stretches (especially if a dehumidifier isn't running consistently).
- Cardboard and paper storage: moving boxes, book bins, old files, wrapping paper.
- Finished basements with hidden voids: behind baseboards, around drop ceilings, inside wall cavities.
- Floor drains and sump areas: constant moisture source.
- Laundry zones: warm + damp + lint.
What they're actually eating
Silverfish aren't hunting your pantry. They're after starches and proteins: wallpaper paste / paper backing, book bindings, cardboard glue, dust and hair buildup along edges, some fabrics (especially if stored damp).
If you're seeing nibbled paper edges or pepper-like droppings along shelving, that's your clue.
Fix it in the right order
1) Dry the basement like you mean it
Set a dehumidifier to 45–50% and keep it running through the humid months. Empty it daily or run it to a drain. Make sure downspouts carry water away from the foundation. If you've got condensation on cold water pipes, wrap/insulate them.
In neighborhoods like White Oaks and Westminster, basements can be damp simply from grading and downspout runoff—fixing exterior drainage makes a noticeable difference.
2) Remove their favourite storage
Replace cardboard with sealed plastic totes. Keep bins off the floor (even a few inches helps). Store books and papers upstairs if possible, or in sealed containers with desiccant packs.
3) Clean the edges, not the middle
Silverfish travel along baseboards and corners. Focus on: vacuuming perimeter edges, under shelving, behind the washer/dryer, along the furnace room wall line.
4) Seal the "quiet cracks"
You're not trying to make the basement airtight. You're removing easy harborage. Seal: gaps where baseboards meet concrete, around pipe penetrations, utility entry points, along window frame gaps.
A simple sealing pass can reduce activity a lot, especially in finished basements in Sunningdale and Masonville where small gaps behind trim are common.
5) Monitor so you know if it's improving
A few sticky monitors along baseboards and near drains will tell you where activity is concentrated, whether the issue is fading or stable, and if you're dealing with silverfish, firebrats, or a mix.
When professional service is worth it
If you're seeing them in multiple rooms, or you've got a finished basement with repeated activity, a professional approach helps because the work is inspection-driven (finding the real harbourages), focused on voids, cracks, and perimeter travel routes, and paired with humidity and exclusion recommendations.
You don't need dramatic measures. You need consistent control.
Quick checklist
- Basement humidity held at 45–50%
- Cardboard removed or sealed
- Perimeter edges cleaned
- Gaps sealed at baseboards and penetrations
- Monitors placed and reviewed after 2–3 weeks
FAQ
#### How fast will silverfish go away once I run a dehumidifier?
You'll usually see fewer sightings within 1–2 weeks, but it can take a full month for the basement to dry out and for harbourages to calm down.
#### Are silverfish coming from the drain?
They can be active around drains because of moisture, but they're more often living in cracks, wall voids, and storage areas nearby.
#### Do I need to throw out all my stored items?
Not everything. Prioritize paper/cardboard and anything that feels damp or smells musty. Move items into sealed bins and keep them off the floor.
#### What's the difference between silverfish and firebrats?
Firebrats prefer warmer areas (near furnaces, hot water tanks). Silverfish tolerate cooler, damp basements. A proper ID helps target the fix.