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andersp 01-07-2008 09:16 AM

Subfloor slopes downward from exterior wall for 2-3ft then levels off...
Hi Folks,

I recently removed all carpets, laminate, etc. in my 35 year old house to expose the subfloor and prepare the house to install hardwood flooring. Along one of my exterior walls, there is a noticeable downward slope away from the wall that extends 2-3 feet (i.e. the width of one sheet of the plywood subfloor). This slope extends across the entire wall of the house. I went to the basement to investigate, and it looks like the main support beam, which is completely level across the entire house, that sits on top of the foundation has settled over time. The reason I assume it has settled is that there is a small gap above the main beam in the concrete foundation where the beam rests. The supporting beam is perpendicular and to the wall in question, and directly in the middle. It seems like the floor joist that is sitting on the foundation has stayed in the same place over time while the rest of the house sunk. It looks, from looking below, like the last two floor joists from the wall have been pulled off the main support beam and are still connected to the subfloor. There is a small gap between the last two floor joists and the main support beam (not including the joist sitting on the foundation). The gap is approximately 1/4" under the first joist off the foundation wall, and 1/8" under the second joist, which explains the slope above. Can I fix this issue without having the raise the main support beam across the entire house? My first reaction was to pull the last sheet of subfloor from the wall and shave the joists to level them, but the gap between the joists and the main beam leaves me to wonder if this is the most important issue that needs to be addressed instead.

Thanks in advance!

glennjanie 01-07-2008 04:19 PM

Welcome Andersp:
I would need some pictures of this one to give you any sound advice. It sounds like some posts in the basement didn't have any footer under them, which allowed them to sink. Is the basement floor cracked? You may need to cut square holes in the basemet floor, dig down to bearing soil with post hole diggers and place some new concrete to hold the house up. Then jack it and wedge or space it up until the whole floor is level.
Please post some pictures to give us a more detailed look.

ToolGuy 01-07-2008 04:35 PM

I read this earlier but really had a hard time piecing it together. Definately some pics woud be helpful. If you have a hard time uploading them here, you may want to try, then provide us a link or use the image button when you write your post. Sorry I can't be of much help. What Glenn says about the posts sinking makes the most sense, but then it seems like it would be a gradual slope to the center of the house. However, this you describe seems like something is catching the subfloor at the outside edge, preventing it from sinking with the rest. Some photos of the floor, the basement, and even the outside of the house, may help us spot the problem.

andersp 01-07-2008 04:37 PM

1 Attachment(s)
Thanks a lot for taking the time to read my post. I did some research, and I am very confident that I have the same problem as the attached picture/article. If I were to cut the subfloor in the middle of the first joist (the joist that has a 1/4" gap underneath it between the joist and the main beam) from the foundation wall, I would be making a cut approximately 2-3" from the wall upstairs. So, if this is the solution, and the floor drops back down, I will also need advice on how to address the final 2-3" of subfloor that will end up being higher than the rest of the floor once the joist drops back onto the main beam. I assume I would just cut it out and install a new subfloor using braces since it's only a few inches, an no one would really ever walk along the edge of that wall.

Thanks again!

ToolGuy 01-07-2008 04:54 PM

Way to Go, Andersp!

If that's not the issue, then it's got to be something along that track. As for cutting it, I'd get up close to the wall with a reciprocating saw (SawZall) and just cut enough to let it drop back down to the joist. The nails will probably still hold it up, but a whack with the hammer will fix that. Then I'd put in a few more nails or screws, seeing how the original nails have now been disturbed. Wouldn't want to get a squeeky floor.

If you have to cut it 2 or 3 inches away, you can fill the remaining space with 1x lumber (which is actually 3/4" thick), as it would be more ridgid than a narrow strip of plywood.

andersp 01-07-2008 05:06 PM

Thanks Tool Guy! I'm pretty sure that is the issue as the main beam is perfectly level across the house. What happens if the joist doesn't drop after cutting it? For example, could the joist "warp" into that permanent position over time? If it doesn't drop, how could I pull the joist back down to the main beam and keep it there?

Thanks again!

ToolGuy 01-07-2008 05:15 PM

The joist?

Okay, we really need some pictures. :)

I see the joist is down to the 'settled' level, while the plywood subfloor is lifted away from it because of being snagged on the sill plate. Is there a gap between the joist and the subfloor, as shown in the drawing? Just trying to get a clear picture here. :o

andersp 01-07-2008 05:33 PM

Sorry, my camera is out of commission :( However, the gap is not between the plywood and the joist, it is between the joist and the main beam that would normally support its weight. The subfloor is screwed to the joist, so the subfloor still rests on the joist nice and flush with no gap. Therefore, it looks as if the subfloor pulled the joist off the main beam.

Does this make sense? I could draw a picture with Paint if you still need a better understanding.


ToolGuy 01-07-2008 06:01 PM

I get it now. So, the joist is bent. To be honest, I don't know if it will unbend. It might drop and leave a dip in the floor.

What I'm wonder is why the joists bent. I mean, since the joists are to span the distance between the foundation wall and the main beam, it seems it would be an even slope the whole distance.

andersp 01-08-2008 07:43 AM

Well, you are close in your drawing, but the joists run parallel with the wall in question. So, you have the main beam that runs directly into the middle, perpendicular to this wall, and the joist running parallel with this wall and sitting on the main beam. Where the two joists (one for each side of the wall) meet in the middle over the main beam, there is a 1/4" gap under each one.

Does that make sense?

Another catch is that I have a bedroom wall upstairs that runs directly over the beam. So, I'm not sure how to make the cut in the floor so that it releases from the wall and drops because I assume the wall goes over the foundation since it might be a load bearing wall? I'm going to another computer to upload a picture that I took with someone elses camera. Wait until the next post...

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