big notches

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  #1  
Old 12-20-06, 09:23 AM
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big notches

I hope you don't mind that I posted this under the code forum as well, but I think contractors and subs might have real world experiences to supplement the strictly "by the book" answers.

I won't say who did it (to protect the guilty), but prepping for recessed ceiling speakers, they really "notched" bottom of a joist:

Joist is 2x10 (old, behind plaster and lath, so is the full 10").
Span is 13'.
Two notches, each located 3' in from end of span.
Notches are 2 1/4" deep, 7" wide.
Sawzall mistake made one cut (blade's width) overshoot top of a notch by almost 1 1/2".

So joist is effectively a modern 2 x 8 with a 1" deep, 1/8" wide cut.
Joist is in ceiling of dining room under mostly bedroom with a bit of hall.

QUESTION:
Is it safe? Seems so overengineered to begin with that I shouldn't worry. Should I squirt pl400 into the cut? Even if it is not quite code, is it dangerous? Or just squeaky or some other annoyance? Or nothing at all?

Thanks
Randy
 
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  #2  
Old 12-20-06, 01:58 PM
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Whoever did that is a complete idiot! The joist is ruined and it is not safe. You CAN'T notch a joists like that period! A joist can have a hole drilled into to it no less the 2" from the bottom. This joists has to be reinforced. Call youself an Architect or Engineer and let them come out and look at it to tell you what the fix should be and deduct the cost from the unprofessional who did it.
 

Last edited by twelvepole; 12-20-06 at 02:49 PM. Reason: Quoting entire post not necessary. Quote deleted.
  #3  
Old 12-20-06, 02:33 PM
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[QUOTE=Joe Carola;1094478]The joist is ruined and it is not safe.QUOTE]

Really not safe at all? Is it because a 2x8 can't span 13' safely or is it now effectively less than a 2x8? All joist weren't cut - just one in the middle of room.

Randy
 
  #4  
Old 12-20-06, 03:01 PM
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The reason notching of joists is not recommended is because fibers on bottom of joist go into tension as those on top compress. This is important for floor strength, straightness, and solidity. When you notch, you reduce the integrity and stability of the joist. If notch or hole in joist is in the wrong place or too big, then you can have bounce and sag and possible joist failure.

Building Code says: "Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends shall not exceed
one-fourth the depth of the member. The tension side of
members 4 inches (102 mm) or greater in nominal thickness
shall not be notched except at the ends of the members. The
diameter of holes bored or cut into member shall not exceed
one-third the depth of the member. Holes shall not be closer
than 2 inches (51 mm) to the top or into member the member, or
to any other hole located in the member.Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch."
 
  #5  
Old 12-20-06, 06:56 PM
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rf1031:
I answered you in the above forem thread, but will answer it again here. Your joist was not over engineered. For a 2 x 10, you are approaching the limit with a 13 foot span. However, you did not say what type of house you have, nor did you say where in your house the joist was. The joist will not break, but it has been substantially weakened. It will begin to sag in a short period of time. This is a serious matter, and you should keep you eye on this joist. The above answers were correct. You made a very bad decision on making those cuts. You are going to have to deal with this in the near future, and the sooner the better. Good Luck
 
  #6  
Old 12-20-06, 11:40 PM
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Randy i just had to repair a situation similar to this one except my joist was drilled through the bottom 4" with a 4" bit for plumbing. The awnser i got back from a floor engineer was a 2x10 1/3 the span glued and screwed with 3" lags 2- rows 12" o/c. and make sure the new 2x10 also sits on the bearing point to assist in the load sharing. this should work for you. But like everyone else said this needs to be fixed ASAP.
P.S. Hey twelve...beauty code quote...hehe
 
  #7  
Old 12-21-06, 07:50 PM
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Originally Posted by Jack the Contractor View Post
rf1031:
Your joist was not over engineered. For a 2 x 10, you are approaching the limit with a 13 foot span.
Thank you all for your replies, but I'm surprised at that. I had tried to research joist spans and found this web site: http://www.hbtownhall.com/pdf/JOIST%20SPAN%2040LB.pdf

In that chart, for 20 lb dead load and 40 lb live load they have max spans varying from 14' to 17' (2x10s 16" o.c.) for all woods except grades of #3. Since the room above is a sleeping area, I believe that reduces the live load to 30lbs, which should allow an even longer span. I don't know what kind of lumber this joist is, but it is old and really hard, and thicker than a modern 2" board.

I also thought that notching would reduce the strength to be equivalent of the shortest undamaged section. In other words, if I took a sawzall and lopped off the bottom 2" of a 2x10 for the entire middle third of a span (an absolute no-no), doesn't that just turn the 2x10 into a 2x8?

Obviously I might be grasping at straws for false comfort here, but I really don't understand why this would not be so. Twelvepole, I know that code says to never do what was done here, but if it was a 2x24 here, no one would be concerned for safety or sagging. If it had been a 2x6, though, it would probably have already snapped. Mine is in the middle, so I just don't know enough and am looking to find out the real risk.

Thanks again

Randy
 
  #8  
Old 12-21-06, 08:22 PM
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big notches

rf1031 -

In answer to your example of cutting out the bottom of the middle 1/3 of the span - Strange things happen when you have abrupt changes in the thickness of a member (stress concentrations and that sort of thing). This is the reason you can get away with more if you are drilling round holes instead of cutting square holes. Square corners give an easy place for a crack or shear to take place.

I am not familiar with the real nuts and bolts details of all of all these code requirements, but hey are generally based on actual tests run by the lumber suppliers and/or schools to justify a way to solve common problems and continue to use wood.

Dick
 
  #9  
Old 12-22-06, 05:15 AM
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rf1031:
We here have been trying to help you with your questions. Yet, you have come back arguing with us. After reading your last post about me being wrong, I got up and went out in below zero weather and got my builders bible and I am now looking at the REAL span tables. Not something you see on a web site. For a 2 x 10 if your floor joists are 12" on center the span is from 13'5" to 16'10". Now I know your joists are not on 12" centers. For 16" centers they are 11'8" to 15'2". This may be you ? Now if your joists are 24" OC like most are the span ranges from 9'6" to 13'5". Now I said that you are approaching the limit with a 13' span, which you are. You may be actually exceeding it. Now you made some comment about cutting off 2" and making it a 2x8. Well a 2x8 will only span 9'6" 16" OC and 7'9" 24" OC. These are cold hard facts. If you want to think something different thats up to you. There was no need for your smart remark to Twelvepole. She told you correctly. If you want to argue or be smart, talk to me not my friend. We are trying to help you, but you still think you are right when you are not. You made a mistake, you must now pay for it and it will not be cheap. Your the one who cut your joist, not us. Have a good day. I have to go back out in the cold to take my code book and builders bible back to my pickup. I have to put in 20' floor joists today, about 20 of them, 23'3" max span, Douglas Fir 12" OC.
 
  #10  
Old 12-22-06, 05:43 AM
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Originally Posted by Jack the Contractor View Post
rf1031:
There was no need for your smart remark to Twelvepole. She told you correctly. If you want to argue or be smart, talk to me not my friend.
I am truly appreciative of your helpful posts and meant no smartness or disrespect. I am very sorry if you took it that way. I had simply found info that I thought was relevant and might indicate that the mistake was not the disaster that you all imply. Wishful thinking perhaps, but disrespect not at all intended. I did not say you were wrong. I said I was surprised. And I was surprised. I don't know how else I could have asked more politely. I am sorry if the table I found gave me incorrect info and that you had to trudge into the cold for me, but I thank you. I hope you see it now in the spirit intended.

Also, I know that codes are there for a reason and was not trying to be argumentative. I had posted here as well as on the code forum specifically to find out if code was overkill for worst case loads or whether a lesser standard was still safe 99% of the time. I thought my reply to Twelvepole was clarifying the example, not smart-alec backtalk. I am very sorry if it did not come off that way.

Again, my sincere thanks to all. And best wishes for the season.

Randy
 
  #11  
Old 12-22-06, 06:56 AM
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Originally Posted by rf1031 View Post

I also thought that notching would reduce the strength to be equivalent of the shortest undamaged section. In other words, if I took a sawzall and lopped off the bottom 2" of a 2x10 for the entire middle third of a span (an absolute no-no), doesn't that just turn the 2x10 into a 2x8?



Randy
Randy,

Ripping a 2x10 down to a 2x8 does not make it a 2x8. I've been a Framing contractor for many years and this has been brought up a few times. The first time it was brought up was about 16 years ago when I ordered 2x6's for ceiling joists and the lumberyard for some strange reason sent me 5-1/2" joists but they were ripped. I called the lumberyard up and asked what happened and they said that they ran out of 2x6ís and ripped them out of 2x12's.

I called the Architect and asked him about that and he said that you can't do that. The lumberyard had to come back and pick up their fake 2x6ís. I don't know the exact reasons why but you can't. It's like if you are using 2x8's for a floor joists and you run out and come up one short. If you have an extra 2x10 lying around, you rip it down to a 2x8. You can't do that either. I will call an Architect and ask him why but ripping 2x8's down to 2x6's and 2x10's down to 2x8's and ripping 2x12's down to 2x10's and using them for joists you can't do as far as I've been told.

Sometimes you can do it with lvl's depending on how much like I just did this week, but I called the Architect up and asked him first because it was a small window header.
 
  #12  
Old 12-22-06, 07:41 AM
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" called the Architect and asked him about that and he said that you can't do that. The lumberyard had to come back and pick up their fake 2x6ís. I don't know the exact reasons why but you can't. It's like if you are using 2x8's for a floor joists and you run out and come up one short. If you have an extra 2x10 lying around, you rip it down to a 2x8. You can't do that either. I will call an Architect and ask him why but ripping 2x8's down to 2x6's and 2x10's down to 2x8's and ripping 2x12's down to 2x10's and using them for joists you can't do as far as I've been told."

I believe it has to do with the way lumber is graded as it is cut at the mill. Knots or other defects that are acceptable in a 2x12 [i e, do not compromise the minimum expected load-bearing strength for the grade selected] can be large enough to be unacceptable in a 2x6 of the same grade. So indeed it is unacceptable to cut down #3 2x12 into 2x6s and expect them to also grade out at #3.
 
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