# Cluster flies in Calgary homes

> Cluster flies in your Calgary home? Seal south and west wall gaps by late summer. Written quote after inspection.

Canonical: https://www.frameworkpest.ca/cluster-flies-calgary/
Last updated: 2026-10-27

Cluster flies

Calgary and area · Fully licensed and insured

Cluster flies get into Calgary homes in late summer through gaps on sunny south and west walls. We seal those gaps and treat where needed. Fully licensed and insured; written quote after inspection.

[Request a written quote](https://www.frameworkpest.ca/contact/) [Call 825 747 5787](tel:+18257475787) [Text a photo](sms:+18257475787)

_Photo: Unknown, [Public domain](https://commons.wikimedia.org/wiki/File:Winstone_Ltd_-_Images_of_houses_using_Winstone_products_-_Two-storey_house_with_tiled_roof_and_stucco_exterior_(73985).jpg), via Wikimedia Commons_

## How it happens

In late summer they gather on warm south and west walls and crawl into gaps behind siding and trim. Calgary’s Chinook swings can take a wall through several freeze-thaw cycles in one winter, and each cycle works sealant and trim joints loose. A joint that was tight in July can be open by February.

## What we do

1. Inspect south and west walls, windows and soffits.
2. Seal gaps around trim, siding and vents.
3. Treat where needed.
4. Give you a written list of what was sealed.

_Photo: Achim Hering, [CC BY 3.0](https://commons.wikimedia.org/wiki/File:Caulking.jpg), via Wikimedia Commons_

## What you can do today

- ☐ Repair torn window screens.
- ☐ Caulk gaps around window trim.
- ☐ Note where flies gather.
- ☐ Book sealing for August.

Background reading: [exclusion vs bait stations](https://www.frameworkpest.ca/insights/exclusion-vs-bait-stations/).

## Related reading

- [pest exclusion engineering](https://www.frameworkpest.ca/services/exclusion-engineering/)
- [Framework Pest home](https://www.frameworkpest.ca/)
- [stop wasps nesting in soffits](https://www.frameworkpest.ca/wasp-prevention-calgary/)
- [air sealing explained (referral)](https://www.frameworkpest.ca/air-sealing-calgary/)
- [Calgary pest season guide](https://www.frameworkpest.ca/guide/)
- [attic sealing in Calgary vs Airdrie](https://www.frameworkpest.ca/attic-sealing-calgary-vs-airdrie/)
- [pest exclusion terms explained](https://www.frameworkpest.ca/glossary/)

## Questions

### Why are there cluster flies in my house in fall?

They look for sheltered gaps on sunny south and west walls to spend the winter. On warm winter days they can wander indoors and gather at windows.

### When should I seal?

Late summer, before they move in. In Calgary that usually means August into early September.

### Can I stop them myself?

You can caulk gaps around windows and trim and fix torn screens. High gaps and soffits are easier and safer with a pro.

### What does it cost?

Most cluster-fly jobs land between $100 and $1,500 + GST depending on the severity and how many gaps sit in the walls. We price it once we have seen the building. Inspection is complimentary when you proceed with the recommended service.

### Will they come back?

New gaps can open with freeze-thaw. We document what we close.

## Show us the gap.

Text a photo, call, or request a written quote.

[Request a written quote](https://www.frameworkpest.ca/contact/) [Call 825 747 5787](tel:+18257475787) [Text a photo](sms:+18257475787)