--- title: Why is it necessary to cut the joists when installing Belt-Drive Whole House Fans? description: Here is some information explaining why it's necessary to cut the joists when installing the belt-drive whole house fan. --- [Skip to content](https://help.gibraltarbuildingproducts.com/migration/en/knowledge/why-is-it-necessary-to-cut-the-joists-when-installing-belt-drive-whole-house-fans#main-content) English Show submenu for translations ![GBAD Full Color.png\]](https://help.gibraltarbuildingproducts.com/hs-fs/hubfs/GBAD%20Full%20Color.png?height=40&name=GBAD%20Full%20Color.png) - [Default HubSpot Blog](https://semetals-1971711.hs-sites.com/blog) Open main navigation Close main navigation - [Default HubSpot Blog](https://semetals-1971711.hs-sites.com/blog) - English Show submenu for translations - Go to www.gibraltarbuildingproducts.com Go to www.gibraltarbuildingproducts.com Hello. How can we help you? - There are no suggestions because the search field is empty. 1. 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The reason the belt-drive installation requires the cutting of joists is the Air Vent shutter specific for that unit. Air Vent belt-drive motors require that the shutter vanes all open and that the vanes be directed/oriented in such a way as to direct airflow to the motor (to help keep the motor cool and prevent overheating). The shutter vanes cannot fully open unless the joist is cut because the joist will be in the way of some of the vanes. Without cutting the joist the belt-drive shutters cannot open properly. - [Default HubSpot Blog](https://semetals-1971711.hs-sites.com/blog) [![Gibraltar Building Accessories Logo](https://help.gibraltarbuildingproducts.com/hs-fs/hubfs/GBAD.jpg?width=2500&height=777&name=GBAD.jpg "Gibraltar Building Accessories Logo")](https://www.gibraltarbuildingproducts.com/) www.gibraltarbuildingproducts.com Help Center Copyright © 2026, Gibraltar Building Accessories Division