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Old 02-07-2008, 11:27 PM   #1
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floor joists butt ended over wall?


Hi there everyone,

A question popped into my head about my never ending attic project.

I am sistering old stock 2x4 ceiling joists with 2x10 to create a strong enough floor for a big funroom and eventually a bedroom (Can be fun too!).

The old joists are one continuous piece 2x4. Supported by a wall about half way. If I sister these I would need to splice the 2x10 above the wall by overlapping them.

However is there anything to be said against butting them against each other directly over the load bearing wall, nailing it along the whole length to the old stock and strengthening this joint with a bolted on piece of 2x10 sandwiched at the other side?

I am thinking it must be stronger to have the sister directly attached to the old joist all the way then splicing it half way. Also I would keep to the 16"OC which makes it easier to layout my ply later.

Your opinions are greatly appreciated. Have a great day all.

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Old 02-08-2008, 09:43 AM   #2
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floor joists butt ended over wall?


Run em past the old ones and overlap on the bearing wall. Dont butt em, that will only get ya in trouble later on

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Old 02-08-2008, 01:48 PM   #3
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floor joists butt ended over wall?


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... Supported by a wall about half way.
Does this wall have support below it?
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Old 02-08-2008, 07:24 PM   #4
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floor joists butt ended over wall?


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Does this wall have support below it?
Thanks for helping me out here. It sits on the floor joists with a girder running about 36" from it. Looks all original, House built in about 1912.
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Old 02-08-2008, 07:34 PM   #5
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floor joists butt ended over wall?


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Run em past the old ones and overlap on the bearing wall. Don't butt em, that will only get ya in trouble later on
Appreciate the reply, thanks this is a great forum, even though of course sometimes we all hear things we don't wanna hear.

The reason I was wondering was that it appears to be totally acceptable to splice ceiling joists that way provided you use a 2x minimum 24" long splice plate. Of course the load requirement is about double that which is why we use bigger joists to start with.

Just a thought.
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Old 02-09-2008, 09:33 AM   #6
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floor joists butt ended over wall?


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Originally Posted by Oldhouseowner View Post
Hi there everyone,

A question popped into my head about my never ending attic project.

I am sistering old stock 2x4 ceiling joists with 2x10 to create a strong enough floor for a big funroom and eventually a bedroom (Can be fun too!).

The old joists are one continuous piece 2x4. Supported by a wall about half way. If I sister these I would need to splice the 2x10 above the wall by overlapping them.

However is there anything to be said against butting them against each other directly over the load bearing wall, nailing it along the whole length to the old stock and strengthening this joint with a bolted on piece of 2x10 sandwiched at the other side?

I am thinking it must be stronger to have the sister directly attached to the old joist all the way then splicing it half way. Also I would keep to the 16"OC which makes it easier to layout my ply later.

Your opinions are greatly appreciated. Have a great day all.
I too am an owner of an old house (1911) that I am currently rebuilding from the inside out, one room at a time (looooove that plaster!).

First of all I am not a structural engineer (electrical) but I work with a group of them and I regularly consult them for business and personal issues. I've learned quite a bit about structures over the course of my career but by no means am I a professional SE. I do all my construction, including carpentry so I have some practical experience therein as well. That being said, here are a few pennies for your pocket.

First of all, you mention 2x4 lumber as being the existing joist size? I've seen some very questionable things in my house which are totally code illegal by today's standards but 2x4 seems insane! You did mention that this are these are attic ceiling joists but still, they seem grossly small even for that application.

From your post, it appears that you are beefing up the attic floor to create a livable space. 10" lumber seems reasonable but you may want to check with a design professional to make sure. At the end of the day, it will be the 2x10's that transfer the floor load to the support walls and you want to make sure that the size will prevent excessive deflection. For this you'll need to consider the lengths of the free spans that they'll be subjected to.

My house is balloon framed and all the existing lumber is old growth (the wood is so hard I usually have to pilot drill before screwing into it to prevent cam out). The exterior wall studs extend continuously from the foundation sill all the way to the top plates on the second floor. The floor joists are continuous as well, spanning 36+ feet without break (there is a central load bearing wall running perpendicular at about 1/3 the span of the house for supplemental support). Last time I was at the lumber yard, I didn't see too many 40' pieces of lumber! Pretty interesting.

There is nothing wrong with splicing above the load bearing wall. This is done today, often to allow the use of standard length lumber. Usually though, the pieces overlap by a foot or two, i.e. they do not butt together. In your case, if you don't need to splice, then I wouldn't. Either way, once the new framing is in, take the time to properly block it over the L/B wall to prevent rolling of the new joists. If sistered to 2x4's, the blocks will need additional cuts to fit the 2x4/10 interface.

I tend to err to the cautious side when I'm doing something that is structural in nature. That being said, I often consult my SE pals or if not practical, go for something that I know will work (read: oversized!). At my work where the structures are for mass transit, those bozo's design with a 150% safety factor anyway!

Good luck,
Jimmy
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Old 02-09-2008, 10:05 AM   #7
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floor joists butt ended over wall?


If you butt them,just make sure you get 1 3/4 bearing on your wall from both sides.
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Old 02-09-2008, 10:38 AM   #8
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floor joists butt ended over wall?


Johnrem: I respectfully disagree on this; He is actually building a new floor system that will be taking the total load. With only 1 3/4" of a joist to take this load is a disaster waiting to happen. A joist will DEFLECT under load, If you can picture that bending moment it WILL tend to pull the ends of the joist towards that bending moment and location. That is why you overlap those joists and nail em together and toe them into the plates.
I am willing to bet a case of beer on the fact that if you just butt those joists IT WILL FAIL INSPECTION AND CODE. And BLOCK EM to prevent twisting
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Old 02-09-2008, 11:18 AM   #9
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floor joists butt ended over wall?


If he does butt them ,and the wall is 3 1/2 ",he must be careful to to have these joists meet in the center. Any less could be a problem and possibly fail inspection.I don't have code book in front of me but this is something I seem to remember from the past. agree about solid bridging to prevent twisting,among other things ,such as framing(2x4)directly below new joists to transfer load down to a solid footing,but I'l leave this for the engineer. Maybe some here could help us with the facts on the codes.
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Old 02-09-2008, 11:57 AM   #10
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floor joists butt ended over wall?


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If he does butt them ,and the wall is 3 1/2 ",he must be careful to to have these joists meet in the center. Any less could be a problem and possibly fail inspection.
You would NEVER EVER EVER but two joists together like that. You always run past.
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Old 02-09-2008, 12:11 PM   #11
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I do wonder what the code book would say about that situation.
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Old 02-09-2008, 02:29 PM   #12
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floor joists butt ended over wall?


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I do wonder what the code book would say about that situation.
Not a lot that I could find. You can apparently butt CEILING JOISTS over a bearing wall if you use a splice plate. However I can't find any info doing this to FLOOR JOISTS, but I can't find anyone forbidding it either. My thought was lining up the 2x10 and the old stock ceiling joist as well as a splice plate for the butt ends would make for a very rigid floor.

Skymaster, very good point with the deflection pulling the ends together though. That is about the most logical explanation I have heard about it.

Jimmy I hear you with the old house! I agree - I wish drywall had been invented 60 Years or so earlier. As an added bonus the old owner had screwed drywall over the old lath which made for an interesting new bathroom reno a few years ago.

The old stock 2x4 were quite a common way to frame the ceiling in the old days here allegedly. They span about 30" with a bearing wall in the centre. 2x10 are sufficient for the span I've got with a ceiling finish attached to them. It's quite beautiful what kind of wood they had in the old days - 2x4 that are actually 2x4 in 32 foot or so lengths?

Thanks for your help folks any more feedback is of course appreciated
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Old 02-09-2008, 05:22 PM   #13
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floor joists butt ended over wall?


ok.FYI.this is what I found.This my not be true everywhere but this is what Ohio says:OHIO BUILDING CODE,THROUGH APRIL 2006,chapter 5,floor framing,R502.6 bearing,"the ends of each joist,beam,or girder shall have no less than 1.5" of bearing on wood or metal and not less than 3" on masonary or concrete ,ect..."also R502.6.1 floor systems "a wood or metal splice with strenth equal to or greater than that provider by a nailed lap is permitted". I guess you could think of the splice being similar to a bottom cord of a roof truss.They always have seams like this.Old house owner's idea would work and pass code in Ohio,and big jimmy's post was right on all the way.I am sorry but a floor joist that is sized correctly ,would NEVER deflect so much as to fall off a bearing of 1.5" or more.What I was referring to in post #7 was that if he ended up with less than 1.5" bearing,because of sloppy work,then he would fail inspection.If I were you,oldhousebuilder,I would check with your local inspector.They won't tell you how to build,but they will answer specific questions.Now I do believe skymaster owes me a case of beer but one problem,I don't drink(diet soda only) so give the brew to your crew on me.
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Old 02-09-2008, 09:50 PM   #14
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floor joists butt ended over wall?


FYI.this is what I found.This my not be true everywhere but this is what Ohio says:OHIO BUILDING CODE,THROUGH APRIL 2006,chapter 5,floor framing,R502.6 bearing,"the ends of each joist,beam,or girder shall have no less than 1.5" of bearing on wood or metal and not less than 3" on masonary or concrete ,ect..."also R502.6.1 floor systems "a wood or metal splice with strenth equal to or greater than that provider by a nailed lap is permitted". I guess you could think of the splice being similar to a bottom cord of a roof truss.They always have seams like this.Old house owner's idea would work and pass code in Ohio,and big jimmy's post was right on all the way.I am sorry but a floor joist that is sized correctly ,would NEVER deflect so much as to fall off a bearing of 1.5" or more.What I was referring to in post #7 was that if he ended up with less than 1.5" bearing,because of sloppy work,then he would fail inspection.If I were you,oldhousebuilder,I would check with your local inspector.They won't tell you how to build,but they will answer specific questions.Now I do believe skymaster owes me a case of beer but one problem,I don't drink(diet soda only) so give the brew to your crew on me.[/quote]

Last edited by johnrem; 02-09-2008 at 09:53 PM.
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Old 02-09-2008, 10:40 PM   #15
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floor joists butt ended over wall?


Thanks Johnrem, that's very interesting. Finally a code which mentions it. I guess plugging the inspector is the answer.

Hey shouldn't any Beer here go to the guy who started this tread?

Have a great day Guys,

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