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Old 03-14-2010, 09:54 PM   #1
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Cut Joists - How to Repair?


I removed the drywall from the ceiling of my furnace room earlier today to get a feel for how the ductwork is running (I will be updating some of the HVAC as part of a larger project) and discovered something really disappointing.

It seems as though the HVAC contractors who installed the system originally before we bought the house (it is a retrofit on a 75 year old brick rowhouse), cut two joists in order to accommodate the ductwork. The joists are nominal 2x10s, spanning 15'. The joists have been cut approximately 2' from the wall. The contractors must have known they were doing something wrong because they connected the two cut joists with a 2x10 and support this bridge with two vertical 2x4s which just rest on the slab. I know this solution is insufficient.

I know that the best solution would be to use double headers and double trimmer joists connected with joist connectors. Unfortunately, the basement is finished... and my mother-in-law lives down there, so doubling the trimmer joists would be really difficult, but no problem in doubling the header/stronger joists. Will this be totally insufficient? Any thoughts, suggestions, options? I can't get a really clear photo of the problem, but I could sketch it if my description isn't good enough.

Thanks!

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Old 03-14-2010, 11:20 PM   #2
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Cut Joists - How to Repair?


Pictures would be helpful here, but since you said that would be challenging, a sketch would work.

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Old 03-15-2010, 08:04 AM   #3
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Cut Joists - How to Repair?


Andrew- Thanks, it is just tough to get a camera up into the space, given the hvac, pipes, etc. I will see if some additional demo will help, but for now, I have done up a little drawing. The red rectangle is the brick wall, the brown rectangles are obviously the joists (nominal 2x10, spaced a little less than 16" OC, and with a span of less than 15'), the gray box is an hvac supply trunk (12x10) and the green circles is the main soil stack for the house (3"). You'll see that there is a piece of 2x10 bridging the two cut joists, the cut joist on the right butts into the bridge, whereas the bridge butts into the cut joist on the right, not sure if that makes sense, or if it is clear on the drawing, or if it even matters.

Any thoughts? I would really love to avoid having to tear down the ceiling to double up the full joists on the left and right of this areas, but if it is the only option, will do so.

Thanks!
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Old 03-15-2010, 12:00 PM   #4
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Cut Joists - How to Repair?


the header/ bridge needs to be a double that connects to the next full bearing joists. you may need to post down to slab at these two junctures for load support depending on whats on floor above
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Old 03-15-2010, 12:24 PM   #5
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Excellent. Thanks for your response.

So, just to make sure I understand. The header/bridge should be doubled, but it is not necessary to double the full bearing joists on either side? Some of what I have read says that both the header and the joists the header bears on, need to be doubled.

The floor above is our dining room, there are no specific loads bearing on these joists in particular.

Currently the bridge/header is supported by a double 2x4 post down to the slab. Is it OK that it goes only to the slab or should it go to the footer/foundation?
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Old 03-15-2010, 12:37 PM   #6
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Cut Joists - How to Repair?


It's the full joist on either side that should be doubled to cary the load of the 2 cut ones.
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Old 03-15-2010, 12:42 PM   #7
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the outside bearing joists should be dbl but since this is not practical if you joist hanger everything and post to slab with pt 4x4 at bearing joist i feel you will be ok. you need to check if cut joists have sagged and raise if needed when installing new dbl. this is all just my opinion with what you have explained and have to work with without major demo
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Old 03-15-2010, 01:19 PM   #8
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Thanks to both of you.

TPolk- Do you think that doing as your describe would pass an inspection? I am going to be doing some plumbing and hvac work soon which means I'll have an inspector in the utility closet and I'd rather this not become an issue.

Kwikfishron - Do you think it is "code" to double up the outside bearing joists, or just best practice?

It would not be impossible for me to double the joists, but it would involve a lot of demo, destruction, dirt and then a lot of cleanup. I want to do this right, for our sake and for any future homeowners... I am determined that the next owner will not make regular discoveries of incompetence.

If TPolk's suggestion isn't code/inspector friendly, are there any other options short of doubling the joists? How about short sistering the joists? Does Simpson have anything that might help here?

Thanks!
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Old 03-15-2010, 06:34 PM   #9
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I'll tell ya, If your going to have a inspector in there anyway, simply call him or her and ask what they want to see. I've dealt with them so long and have realized that one inspector won't even look at it, especially if he's there for a HVAC inspection, were the other guy (in the same office) will make you go overboard. Personally I’d double every thing up with hangers and see what the say. So if you have to throw a post in later to pass inspection, big deal. If the post are in your way the pull them out later, save and put them back when it's time to sell. Assuming they are not needed to hold the roof up from the basement.

P.S. I changed my mind a little. If there there for only a HVAC inspection act like your fix has always been that way. If you let them know your working on it they might make you pull a framing permit and that would be more $$$.

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Old 03-15-2010, 07:39 PM   #10
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to do it right the header requires the bearing joist to dbl. with out having access to your ceiling you may be looking at moving wires, plumbing etc to dbl the joist. the span the singles are carrying right now is 7.5' pus half the span of the additional joist that are cut. I dont know the load calcs but someone on this site does and could tell you if it will carry just tying into the singles with no post. i would think that code requires a dbl in this case since two are cut, just one would not be an issue. so code compliant dbl but you may be able to get a variance to just post underneath as discussed. you would need to talk to inspections and plead your case
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Old 03-15-2010, 11:17 PM   #11
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If you calculate the header and adjacent joists carefully the system might work without doubling the header and joists.

If you know an engineer or good wood designer it is often possible to calculate an installation like this which makes a lot more sense than tearing out part of the ceiling and arbitrarily doubling joists and headers.

The header will need to span between the two adjacent full span joists. Properly sized and installed face mount joist hangers will be needed where the shorter joists frame into the header and where the header frames into the adjacent joists.

Usually the critical factor when designing floor joists is deflection. Applying an additional concentrated load 2' from the end of a joist doesn't make that much difference to the deflection in the middle of the joist.

Another design factor to be concerned about is the shear at the end of the full span joist when the additional load is applied. According to a very rough calculation, this should still be within the allowable stress.

It is important to check all the critical aspects of the design but the results may resolve your problem in the simplest way.

One of the things that may prove difficult is finding a grade stamp and determining allowable stresses to use for your joists which are 75 years old. My house was built in 1954 and the framing is so dense it is difficult to remove nails from it or drive nails into it! It is undoubtedly much stiffer and stronger than a joist or rafter you would buy today.

Good luck, John aka JayKay
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Old 03-15-2010, 11:24 PM   #12
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Double ONLY if header spans over 4’ : page #30: http://books.google.com/books?id=iwS...joists&f=false

Trimmer and header joists at openings must be doubled when the header span exceeds 4'0". IRC 502.10

Tail joists over 12’ require hangers or minimum 2x2 ledger. IRC 502.10


Be safe, Gary
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Old 03-16-2010, 12:27 PM   #13
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Wow, this is exceedingly helpful. Looks like, for this, that I am just fine!

I will plan on using joist hangers, but it looks like I should be OK without doubling things up. I might double up the header for good measure, anyway!

Thanks again!
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Old 03-16-2010, 06:12 PM   #14
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please dbl header and nail thru first piece into cut joist then add second header. you will need to square up ends of cut joists, i would recommend measuring out from wall on each single and snap a line across cut ones so everything is pretty square and inline. for that pro look

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