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Unread 01-31-2004, 03:32 PM   #1
rat4spd
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sistering 2x6's with 2x10's

If I wanted to strengthen my floor (2x6's) with larger joists, such as 2x10's, would it be alright to notch the 2x10's to sit on the main beam and the sill? I remember, maybe it was bbcamp, mentioning to someone that it was permissible to sister most of the joist and not necessarily extend it to the sill because shear wasn't really an issue. So I would reason that notching would be somewhat of the same issue.

I dont really want to stay with 2x6's if I can get away with larger joists. I'd lose about 4 inches of head room in my already short basement, but I could live with it. I think the only thing that would have to be moved is my cold air return running Perpendicular to the joists. I dont thing lowering it 4 inches would pose much of a problem.

Thanks,

Dave Ames
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Unread 01-31-2004, 05:42 PM   #2
John Bridge
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Hi Dave,

I don't remember your exact situation, but yes, that would be okay. I'm not able to express it like Bob does, but the closer you get to the supports the less depth you need in the joists. He'll probably stumble in here before long.
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Unread 01-31-2004, 06:06 PM   #3
rat4spd
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Hi John, thanks.

I've re-hashed this several times over the last several years with you guys, as I finish up projects and plan for future ones. I had the idea of sistering with larger joists 'cause as one of yer esteemed persons here said, "heck, 2x6's are used for roofs not for floors!" Plus, realistically, 2x6's with a 12 foot span aren't gonna do much to improve L/73 anyway according to deflecto.

Right now the floor is nominal 2x6 oak, 24 O.C., with 12 foor span. There are a few pine looking 2x6's squeezed in on the 12" center, but only 1/4 of the house. Also, quite a few of the oak joists are just plain junk.

My plan is to sister all oak, and put in new ones in betweeen. I'll probably have a new main beam put in first, because it is rather sinusoidal looking, which is of course why my house has hills.

This really isn't in preparation for tile. It's so my stuff (household effects) don't jiggle when I walk, as well as curing the hills.

Dave Ames
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Unread 01-31-2004, 06:37 PM   #4
John Bridge
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"sinusoidal looking"

Love it.

Well, I think your plan is sound. The joists in between the current ones will make a huge improvement in the subfloor. The deflectometer (spelling?) only tells us about the deflection of the joists in the floor system, but deflection BETWEEN the joists (in the subflooring material) is a big factor, too. Our injineers would have a tough time creating a deflecto device for that, though, because the available information from the flooring industry is a bit skimpy. Anyway, two-foot centers are a real problem, as you know.

Bob ought to be checking in. He usually takes weekends off, but he might get curious.
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Unread 01-31-2004, 06:55 PM   #5
bbcamp
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Wazzup?

Can you add more posts to the main beam? Jack posts will allow you to convert your sine wave into a flat line. You can do this over a few weeks so as not to break anything inside.

Your sisters and new joists can be 2x8s, so you won't have to lose as much head room.
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Unread 01-31-2004, 07:06 PM   #6
rat4spd
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Hi Bob. I though about trying to straighten the main beam, but its got 4 posts under it already. It needs one right where my brand new, almost finished bar sits. Plus it looks more like a hodge podge of 2x8 (three wide), with some 2x sitting on top of it flat.

What about scabbing some more to the sides of it, with bolts, instead of nails (like the current one) after straightening it with a bunch of posts.

I rechecked the deflecto for the 2x8's as you recommended. Looks good to me.

If you think the current beam can be saved without a jillion posts, I'd be most inclined not to mess with replacing it. And to be truthfull, I'd have absolutely no problem puttin a wall under 24 of the 32 feet, but I gotta have the bar, and the beam runs right over the top of it. So I really need that last eight feet free.

Dave Ames
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Unread 02-01-2004, 07:37 AM   #7
bbcamp
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Your plan of straightening the beam and then adding additional members to the sides sounds good. After the glue sets up, you can remove the temporary posts where the bar is.
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Unread 02-01-2004, 10:40 AM   #8
rat4spd
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Bob, I see glue would be good for the new beam material, but what would you recommend on the mechanical fastening. By the way, the current beam width if 4.5" by 8 5/8" tall. Putting some 3/4 plywood under the beam gets it to about the height of a 2x10. Some 16 footers ought to do the trick.
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Unread 02-01-2004, 10:52 AM   #9
bbcamp
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1/4" or 3/16" lag bolts will be fine. I don't think thru bolting will buy you anything. You want the fasteners fitting snugly in their holes.

Nails will work, too.
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Unread 02-01-2004, 11:06 AM   #10
rat4spd
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Reason I ask about bolts specifically Bob is that, it appears that some of the sag may be induced by the outside members of the beam "rolling out" some. Looking at the bottom, there is a small gap it many places at the bottom. I haven't definatively measured it over the length, but it's not much. I was thinking that thru bolting would pull all the the many pieces of the beam back together, kind of using the beam to strengthen itself, while adding a substantial amount of new beam with no joints, except in the middle at the 16 foot mark, where a post would be no problem.

Some good size steel plate is definately needed for the posts. I see a couple places where post used to be but the beam smushed some, probably 'cause of that flimsy sheet metal on top of those lally posts.
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Unread 02-05-2004, 02:39 PM   #11
rat4spd
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I made progress. I used a big c-clamp, and pulled the beam back together where the bottom was rolling out and used screws to hold it. It ended up being every couple of feet. I then put six new jacking posts under it, took the weight off what few members were holding it, and lifted it. Turns out only a tree, an oak 4x4 (which was almost all rotted at the bottom), and one steel post were supporting the beam.

I then strung a line from the bottom of the beam on each side, and straightened it out mostly. One end of the house had been jacked up a little high, and the other end was about one inch low. I got the beam straight execpt for about 1/2 inch on one end. After putting a substantial amount of weight on two beams, I'm doing it slowly for the rest. I only got about 4 cracks in the plaster, fortunately in rooms that need dealt with anyway.

What should I do fot footings? This sixty year old concrete is pretty hard.
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Unread 02-05-2004, 02:49 PM   #12
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You have any idea how thick the concrete is? Sounds like you now have 6 posts where there were only 3 before.

To be totally correct, you need to sink footings down to undisturbed soil or below frost line, whichever is deeper. These footings would be about 18" square. However, if you are building a load bearing wall for this beam, then you could use the floor slab as is, since the load would be distributed over a bigger area.
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Unread 02-05-2004, 03:20 PM   #13
rat4spd
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The floor is only about 4" thick. I intend on leaving only 4 posts, maybe 5 when all is said and done. But I 'spose since the floor is only 4", it should have footings. I do plan on putting a wall under probably 20 feet of the beam eventually, but I don't know when that'll be. Couldn' take too long to put footings in. It might be worth the peace of mind until the basement project happens.

The floor is probably 4 feet under the frost line, so how thick would footings need to be.

Thanks
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Unread 02-05-2004, 07:06 PM   #14
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15 to 18 inches should do it. Did the other supports have footers?
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Unread 02-05-2004, 07:39 PM   #15
rat4spd
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No footings for any of the existing or original supports. The original three (of which two I removed) were 4x4 oak, set right on dirt, with a spike through the bottom. The floor was poured around them.
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