Floor Joists

[upnorthguy]

Hello! I live in a home that was built in the 40's. right now I am in the middle of gutting my main floor and 2nd floor. The floor joists on the 2nd floor are sagging, not a suprise since they used 2x6, 24 oc, 16 foot span. Idiots. Anyways, looking at all my options(I cannot put a beam in the middle of the span). I was going to just sister 2x10's to the sagging joists to give more rigidity and level out the floor. However there is about 4 joists that need to be completely replaced(where the stairs are) I plan to completely take out the stairs and start fresh. All the joists are connected straight to the 2x4 framing of the house. There is no joist plate.

Instead of sistering to the sagging 2x6, can I just go on the opposite side of the 2x4 and attach it that way? And then either leave in the sagging joist or cut it out once the new one is in place.

My father in law is leary of me taking out all of the current subfloor and then replacing it one joist at a time, he's thinking the subfloor is giving the house some strength. Is he crazy? If I rip all the subfloor up and then replace one joist at a time, and replace with new subfloor within one weekend do you think the structure of the house will be okay?

Appreciate any help.

Thanks

[HayZee518]

try an engineered beam in place of the 2X10. its not as heavy as two 2X10's and will aford you a place to fasten joist hangers.

[upnorthguy]

Thanks for the reply, but I'm not quite understanding where I would hang joist hangers.

[pushkins]

From your description I think the style of framing your talking about is called Balloon Framing.
Site unseen if it were me I would never remove all the floor joists or sub flooring at the same time, remove one section and replace it at a time. In balloon framing floor joists are often used as a form of strengthening of the side walls to stop bowing in and or out, likewise the sub flooring offers a form of stiffening.

The max. span for a 2x10 SPF on 24" centers is 13' 4".
The max. span for a 2x12 SPF on 24" centers is 16' 3".
Now before you say " why so big and so close spacing, 2x6's got the house this far".....50 years ago they used aged lumber or old growth lumber, now they use tree's that are much younger.

If you don't have the room for the 2x12"'s I'd use the 2x10's and put them on 12" centers that will get you up to 16' 10", this way you can leave the existing joists in place and only have to remove every 4th existing joist (12"...24"...36"...48") that would be in the way. This also allows you to work in roughly 4" wide sections at a time and replace new sub flooring sheets as you go.

With balloon framing you should have a piece of lumber (ledger) nailed to the inside of your 2x4" wall this is what the floor joists sit on, while the area is open add ledger lock bolts to this ledger.
I've seen (seldom) where they sat the floor joists on blocking added between the studs, if this is your case add a ledger to the wall like mentioned above under your new joists.

[upnorthguy]

Thanks for the reply. I defiantly want to try to stick with 2x10's. I'm loosing quite the headroom the way it is. Look's like going 12 oc might be the way to go.

They do NOT have any ledgers that the joists sit on. They are just nailed to the 2x4 with no support below them. Looks like I will have to add ledgerboards(which is fine because that should double as a fireblock?)

I am a little confused with only having to replace only the 4th joist. If it's 12 oc, wouldnt I still have to replace every original joist? 12'' 24'' 36'' 48'' ?

Because they are only 2x6'' (and are sagging up to 1 1/2'' on 4') I'd either have to sister or replace so theres something to fasten subfloor down to at 24''. (or would I just leave the original joist in at 24'', and when attaching the subfloor I would just have a 24'' on from 12''-36''.

Also when referring to ledger lock bolts, is this a special type bolt? Doing a quick search on google didn't produce any obvious results.

I appreciate your help times 100.

[pushkins]

I am a little confused with only having to replace only the 4th joist. If it's 12 oc, wouldnt I still have to replace every original joist? 12'' 24'' 36'' 48'' ?

Ooops my error, My brain was thinking 16" on center but should have been 12", so your correct in that every 2nd existing joist will come out. You could still only remove the 48" joist and place the new (24"ctr) joist hard against the existing 2x6 joist...so you would have 0".....12".....22.5"(up against existing 2x6).....36".....48"......60"....72"....82.5"....e tc...
If you do it this way glue and screw the new 2x10 to the existing 2x6 simply to stop possible future squeaks of the 2x6 up against the new 2x10.


Ledgerloks are available at lowe's and HD as well as almost all supply houses. the following link will show what they are:
Search results for 'ledgerlok' (2 found) | McFeely's
If you have a good impact driver you can put them in very easily, either that of a socket wrench and some elbow grease.

The ledger wont act as a fire block as it's screwed to the inside face of the framing, this still leaves a cavity up inside the framing between floors.
You might want to talk to your local building inspector about your local requirements regarding fire blocking. Individual 2x material between stud bays should be nailed in place as min. code requirements under IRC.

[upnorthguy]

Do I use a 2x10 for the ledger? And then use joist hangers to attach the new joists? Also just thinking how I will put in ledgers between the 2x4's when the orignal joists are in the way.

[pushkins]

The problem with installing a 2x10 ledger and then using that with joist hangers for your new joists is that you have to remove all the existing 2x6 joists first. However because your existing joists are 2x6 and your new ones are 2x10 you can install a 2x10 or 2x8 ledger under the 2x6's without removing them because your 2x10's will be lower anyway, so the existing joists don't get in the way.

If your referring to the fire blocking between the 2x4 studs, install them from below the 2x6. or for that matter install them as you install your new 2x10 joists. You still should be able to install the blocking between the studs by toe nailing/screwing.
The bearing surface for your new floor joists only needs to be 1 1/2" so the joists can sit only on the ledger.

If you could post a picture you know what they say......worth a thousand words.