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Old 10-12-2006, 12:05 PM  
jpalumbos
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Default Small Floor-jacking Project

I have a 50-yr old ranch-house, and most of the foundation is fine. The only problem is a sagging floor, next to the staircase to the basement. Here's why:

The main construction consists of a center I-beam, with 2x10 floor-joists running from the center beam to the footers. The basement stairway runs next to, and parralel to the center-beam, so the joists on that side can't run all the way to the center-beam. There is a double joist at each end of the stairway (running from center-beam to footer), then another double-joist next to & parallel to the stairway (on the opposite side from the center-beam). The 6 floor-joists next to the stairway run from this double-joist to the footer.

The problem is that the double-joist parallel to the stairs has pulled away from the one of the perpendicular dj's, 1/2" and sags 7/16". Also, about 3 of the floor-joists attached to the parallel dj have pulled away from the dj, and also sag slightly. (Above this parallel-dj is a kitchen wall, with cabinets & fridge against it. Kitchen floor has many squeaky spots.)

I plan to add a 6x6 beam under the parallel dj, that will also support all the floor-joists that attach to that dj. I'll support the new beam with 2 lally columns. The beam only needs to be 8', but I want to extend one end (where the sagging has occured) an extra 4', so that the column is out of the way.

I've read a lot about this, and have seen many warnings about going slow, etc. This doesn't sound too difficult, but I have several questions:

- Do I really need to fill the columns with cement? If so, how is this done? (sounds tricky & messy)
- I guess I need the 1/4" steel plates above and below the columns & jacks. Where do I get these?
- How much footing do I need under the columns? I guess I'll use 4x6 or 6x6 pcs on the floor to spread the load. Is 1 or 2 feet adequate? Could I just use 2x6? (I'm not sure how thick the concrete floor is, but there are no cracks anywhere.)
- I borrowed a floor-jack, which you adjust with a 1" threaded rod at one end. Is this adequate for jacking, or should I buy/borrow a bottle-jack?
- If I need a bottle-jack, how big? (I don't want to buy more than I need, cuz I won't be doing much other work like this.)

Thanks in advance for any input.
-Joe P.



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Old 10-12-2006, 04:34 PM  
jpalumbos
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...Of course, my NEXT project will be attacking the squeaks in the kitchen floor.

Meanwhile, any help with the floor-jacking would be appreciated.
-Joe P.



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Old 10-12-2006, 04:57 PM  
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Default Small Floor-jacking Project

Joe -

The new 6x6 (or whatever you end up with) will be carrying a significant load (The dead and live load intended for the center beam plus the wall loads from above. Your older center beam will carry much less than it was designed for.

Now is not the time to guess what to do. Have a professional take a look at the situation to size the new beam and the footings. He can see the real situation while we do not have the ability to see what the loads are.

You should have footings under the columns and not just some pine. Just because you have no cracks does not mean the floor can carry the load. It has never been loaded this way, so there would be no cracks. Basement floors are known for being minimal and unreliable regarding the thickness.

With the right design, it could be a DIY project.

Dick

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Old 10-13-2006, 12:24 AM  
jpalumbos
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Dick - thanks for your comments. I may not have explained myself clearly: I'm NOT jacking up the CENTER-BEAM, only the double-joist that's parallel to the CB, and on the other side of the stairs. Yes, there is a wall above it, but (after hearing your advise) I'll make sure not to jack it past the point where it starts taking some weight OFF the CB.

I believe that if I spread the load with some steel-plate and heavy duty lumber, I won't have to cut into my floor to pour new footings. (That would change the whole scale of this project.)

More opinions are welcome.
-Joe P.

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Old 10-13-2006, 07:54 AM  
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Using steel plates and scrap lumber will make the project look like a "patch job" and be a red flag when you go to sell.

All the load (wall above and half of floor on each side) you carry with the existing double joists and new beam will be carried by the new posts directly to the "flloor"/footing. It wil not get to the existing center beam like it did, so you are reducing the load on that beam.

You are guessing at best if you think you predict how much load you are picking up.

Dick

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Old 10-13-2006, 08:20 AM  
inspectorD
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Default Hmmmmm.

Instead of all this jacking and beam sizing and the like...why don't you just build a wall 16 OC under the area .
This will disperse the weight evenly and you will not be under ANY point loads.
This will help the double joist with all that load at best.

If you do go the other route you will need to have a footing poured , a typical 12 inch deep by 24 inches square.This will carry any minor loads under the stairs.
If there were any major loads on this beam you would have had a serious issue already. I am also guessing there are no joist hangers on any of these connections....am I correct?

The best advice is always to get someone to look at it that is a professional, get their ideas and work with them.
Maybe you could dig and fill the holes to save some money.


Posting a picture would help alot also.

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Old 10-13-2006, 08:41 AM  
jpalumbos
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OK, Dick, you make a couple of convincing points.

I really didn't want to cut into my floor, but it sounds like I should probably do it. I don't mind doing the work. (the worst of it will be moving everything out of the way that I just put in storage -- thinking I wouldn't have to touch it again for years!)

Now I have more questions:

- how do I find an engineer to assess the situation?
- if I pour footings, what's the easiest/cheapest way to cut into the floor? (I have a hammer-drill & a couple of basic circ. saws, but nothing heavy-duty.)
- will the engineer be able to tell me how deep & wide, etc?
- you make a good point on appearance, and perhaps an I-Beam would look better in that regard. I'm guessing (again) that this won't require a 6" wide I-beam, but it will need to be wide enough to catch the double-joist PLUS the ends of 6 floor-joists. (that's why I was going to use a 6x6.) Any thoughts?

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Old 10-13-2006, 02:25 PM  
jpalumbos
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Quote:
Originally Posted by inspectorD
Instead of all this jacking and beam sizing and the like...why don't you just build a wall 16 OC under the area .
This will disperse the weight evenly and you will not be under ANY point loads.
This will help the double joist with all that load at best.

If you do go the other route you will need to have a footing poured , a typical 12 inch deep by 24 inches square.This will carry any minor loads under the stairs.
If there were any major loads on this beam you would have had a serious issue already. I am also guessing there are no joist hangers on any of these connections....am I correct?

The best advice is always to get someone to look at it that is a professional, get their ideas and work with them.
Maybe you could dig and fill the holes to save some money.


Posting a picture would help alot also.

Insp-D,

Thanks for your input. To answer your questions:

- I'll try to get some (1Mpix) pictures this wkend.

- A wall is an idea I hadn't considered. However, this is in a rather small storage area; a wall is feasible, but would make it a little more cramped. (That's why i wanted to extend my beam from 8' to 12': just to get one of the poles out of the way.) Also, while this would probably support the existing double-joist adaquetly, I would still need to secure the single floor-joists to the double-joist. (With a new 6" beam, the single fj's would just rest on the beam.)

- When you say "dig & fill the holes", I assume you mean cutting into the existing floor for the footing. What's a good way to cut into the floor? What about pouring a 2'x2' footing on TOP of the existing floor?

- Also, what's an easy way to determine how thick my basement floor is?

- Regarding joist-hangers: there are none. It looks like all the joists I've referred to are nailed in with 2 or 3 nails in the end of the joist (through the adjoing double joist). I considered using JH's to shore up the problem joints, but I can't get at one of the sides of the parallel DJ. (It's right next to the stairs.)
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Old 10-15-2006, 09:54 AM  
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Default Concrete holes

Well for starters, to find out how thick your slab is you can drill a hole in the areas you will be installing the future posts. These are concrete filled steel columns usually called "lally" columns for the company that introduced them.
You would not be able to install the footing on top of the concrete. You do not know if there are any voids underneath your slab which will crack in due time if you did.
As far as cutting the floor you can rent a small concrete diamond blade saw, or buy a blade for your skillsaw. This is a meassy job, dust and all .Use a skillsaw you will not care about.

As far as the rest goes you need to find out your loads above before you do any of this. As it was said before this is a high level DIY gig.

Try some professional opinions in your area first, then let us know what answers were given. Mabey we can help from there.



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