Fire Cut Floor Joists

This feature can affect firefighters operating within the building.

Fire cut floor joists.

Fire cut joists will allow the interior of the building to collapse while the masonry walls remain intact. When installing a new joist on a foundation wall you may need to notch the bottom edge so it. All floor framing materials sawn lumber wood i joists trusses and light gauge steel succumb quickly to fire if not protected. Applying a protective membrane such as gypsum ceiling board to all types of floor framing within the structure will provide uniform protection to the structural framing members.

Section r502 10 of the international residential code states that header joists can be the same size as the floor joists when the header joist span isn t greater than 4 feet but if the header joist span is more than 4 feet you ll need to double the header joist and ensure that it s capable of. This cut is designed to act as a safety feature which will reduce the risk that the wall will collapse in the event that there is a fire which burns through the joist. A fire cut joist is designed and installed the same as a typical floor joist with one exception. In the construction of masonry buildings a fire cut or fireman s cut is a diagonal cut along the end of a joist or beam where it enters a masonry wall.

A nominal 2 8 board measures 1 1 2 by 7 1 2 inches cutting the new joist. The space between the beam and the floor boards above was 7 inches so i decided to use regular framing lumber and rip a 1 2 inch off the width of a 2 8 framing member. If the joist burns through somewhere along its length damage to the wall is prevented as the fire cut allows the joist to fail and leave the masonry wall standing. Additional support for the floor joists is achieved by nailing the ends of the joists into headers.

A major concern on which we must now focus is wooden i joists photo 1. At a supporting wall a regular joist has a square cut end whereas a fire cut has an angled cut on the end. Posi joist floors with a variety of build ups have been independently tested to both bs and en standards and those posi joist floors providing 30 minutes fire resistance are listed in the tables below. A fire cut is a cut made at the top of a joist used with a masonry wall such as a brick or stone wall.

1 the wooden i joist consists of an upper flange a center web section and a lower flange. The angled cut is made towards the top middle of the joist from vertical. If the wall does collapse the nature of the fire cut will encourage it to. Fire resistance max joist centres joist depths ceiling details floor deck details 30 minutes 600mm all depths 225mm.

Heavy timber type iv.