floor joists

[dieselfish]

What is the best way to reinforce or replace sagging floor joists? and which way is preferred?

[giddonah]

Best way would be to jack up the floor a bit and sister new joists to support it. I plan on doing that when I get around to redoing the kitchen in the house I'm working on. I plan on going from wall to wall with the new joist(s) (not sure whether I'll do more than just one) for maximum strength. Then, let the floor down on the new joist(s).



Anyone else?

[dieselfish]

This is for my own house it is 81 years old. It is my kitchen also, I tiled it last year and I noticed the sag but didnt have time or money to fix it. I am going to redo the whole kitchen now and would like to rip up the floor and plywood it then retile.

I have never done it before . What exactly is the best way to jack it up , Is a floor jack for cars ok ? then about how much of the floor to jack up ? I a 2X6 enough to use across the joists?

[giddonah]

You'll want to lift with a pretty large surface. A few 2x6's would probably do nicely. I'd use a hydraulic lift (not a car jack), and make absolutely sure you have things VERY stable. You're not lifting very far, just enough to get the new joists under there.

On second thought, you're ripping the whole thing up? Why bother with the jack? What about just tearing everything down to the joists, nailing in the new joists and removing the old joists. You might come across plumbing/wiring run through the joists, but you can cut around them. Or just leave the old joists right where they are...

[dieselfish]

I mean a hydraulic 3 ton car jack. using a 6 foot piece of 4X4 with 2X6 under the joists.

That was kind of my dilema in my first question. SO it would be easily done putting in the new joist and removing the old ones? Never done it bfore, will they come out that easily? I will most likely be redoing plumbing if any. I fear what the joists in the bathroom look like.

[giddonah]

Yeah, that's the kind of jack I was thinking of. If you're redoing the plumbing, are there a lot of wires strung through there too? I'd say it'd be easiest to just drop the new ones in from above. I wouldn't take the old ones out until new ones were in for support. And even then, I might just leave them in there anyway. Unless they're termite infested, or rotting, I can't see why leaving them in would hurt, and all the extra wood would add strength. And you won't have to dispose of it...


I guess my ideas aren't too crazy, nobody has come in here to correct me. :)


Another thought: If things aren't totally gone, you may just need to double the joists that run through the middle of the floor. Or just double every other joist. If it looks good, but just isn't strong enough, it just might need a little support. Kind of like suspenders :lol:

[dieselfish]

I hear ya , thanks

[Sweep]

Why are the joists sagging? What is the size, span and spacing of the orignal joists? Be sure to solve the original problem.

Using hydraulic jacks can be difficult if you need to raise the entire floor. This requires a lot of jacks or temporary beams and the things tend to be unstable unless you can jack them all exacrly the same amount each lift or if you can secure the jack posts to the jacks so they don't fall off the jack when not in compression.

If you only need to raise the joists 3/4" or so, I would use the old temporary bracing technique of a 2x6 at the floor and ceiling on the flat and cut vertical 2x6's the length of the final height wanted plus 1/4" or more. Put the verticals in at an angle (because they are too long by an inch) and hammer the bottoms laterally until they are all vertical or close to it. Use as many as you need to lift the whole floor. Nail temporarily.

If the new joists are going to be deeper be sure to block the temporary upper plate down so the new joists can be installed. I would not count on the old joists to contribute any strength to the new floor so I am assuming the new joists would be deeper.

If the sag is more than 3/4" you might need to cut the bottom half of the old joists at mid-span to make it easier to raise them. Do it after starting the support system so your saw won't get stuck.

Unless the sub-floor is not strong enough, in very bad shape or there is not enough room for tile underlayment, I would try to avoid the unnecessary work of removing it.

[dieselfish]

I havent checked yet but I think they are 2X8 and the span somewhere around 12' . I think they are saggin because the house is 81 years old and have seen alot of traffic. I want to replace the floor because there are alot of creeks and loose hdwood flooring and ceramice tile on the other half that I would like to replace with laminate. I figure ripping it out wouldnt be that much more work.