I am renovating a city townhouse and I need to replace several joists. What is the proper fire cut for a 2X10 joist that I ripped down to 8″. I am using the existing brick pockets with 4″ bearing on each side.
thanks
I am renovating a city townhouse and I need to replace several joists. What is the proper fire cut for a 2X10 joist that I ripped down to 8″. I am using the existing brick pockets with 4″ bearing on each side.
thanks
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Replies
I don't know what a fire cut is but you might be interested in this attachment now that you have weakened your floor joists and added to the amt of vibration you will have to suffer through.
I also note that you refer to the joists seating in a masonry wall. It is possible that these joists were part of the back bracing needed by that wall to remain vertical and that modifying them as you have, has not done the building as a whole, any good.
so what is a firecut anyway?
Excellence is its own reward!
Firecut: A sloping end cut on a wood beam or joist where it enters a masonry wall, to allow the wood member to rotate out of the wall without prying the wall apart, if the floor or roof structure should burn through in a fire.
I've never come across any rules of thumb...I've always thought that if you understand what it's supposed to accomplish (see attachement), you can figure it out visually depending on the wall thickness and depth of the joist pocket.
Steve
There may be a formula but I've always cut no greater angle than necessary. I cut just enough angle to allow for clearance and yet leave enough meat for bearing and load. If the pockets were originally for 2x10" joist and now you've cut them down to 2x8" you shouldn't have to angle cut them. Your problem now is are your joist strong enough to support the floor or were they over engineered to begin with?
Edited 8/11/2003 4:26:01 PM ET by Bob
Thanks for all the info. Dealing with city inspectors I want to make sure everything is to code. There must be some formula for these cuts. I checked my International res. code book but nothing is listed. If anyone has an article on fire cuts I would greatly appreciate it.
Thanks
A Google search for
"fire cut" joist
returns 67 pages, several of which have pictures.
as to the 8" size, if read it that he cut them down to an actual 8", since many older stuctures have full-dimension lumber. i.e. took off 1-3/8 to get 8" full dimension from a 2x10 broad.
OK, I can see that interpretation now that you point it ouit but a new 1-1/2" wide joist will have nowhere nere the same load bearing strength as an old growth 2" joist. It would also need to be shimmed in that pocket to maintain vertical orientation.
Froggy, what is the overall span and layout for this floor?.
Excellence is its own reward!
Make your cut at the top just enough to clear the block,straight line down to the center bearing point.
One might just match the new beam fire cut to the existing fire cut.