2 x 12” floor joists? Why...?

[nereo]

I’ve got something of a mystery.  Reno-ing my home, the core of which is c. 1900 with at least 4 additions.

Currently we are tackling an upstairs “great room” - one of several additions.  It inexplicably had a 6” step up/down from the rest of the upstairs.  Finally pulled up the 20+ year stained, nasty carpet to reveal the VERY squeeky plywood subfloor (see below).  Figured now was the only time to get a look below, and discovered that room is built on 2 x 12” rough joists 16” OC.  But... why?  That seems incredibly overkill. The span is only 17’, and the room is 22 x 17.

Really I have two burning questions;

1) any theories on why the hell they would use 2x12’ lumber when putting up an addition on this one section?  It was previously a one-story living room before they added a ‘great-room’ above it

2) slightly more important:  Subfloor squeeks like hell, even though joists are rock-soil. So I decided to correct the problem.  Pulling up one 4x8’ sheet I found the following:  3/4” TNG plywood that was fastened with 3.5” framing nails and then (presumably later) also fastened with 1.5” drywall screws.  Many of the framing nails have popped.  My choice now seems to be either a) hammer down all the nail pops and possibly add new steel screws, or b) remove all the mishmash of fasteners, pull up each board and then re-lay the subfloor with proper steel flooring screws.

I’m guessing just hammering down the nail pops won’t be a lasting solution, but it’ll take several hours to pull up every framing nail they drove in there.

Thoughts?

[MasterStache]

I’ve got something of a mystery.  Reno-ing my home, the core of which is c. 1900 with at least 4 additions.

Currently we are tackling an upstairs “great room” - one of several additions.  It inexplicably had a 6” step up/down from the rest of the upstairs.  Finally pulled up the 20+ year stained, nasty carpet to reveal the VERY squeeky plywood subfloor (see below).  Figured now was the only time to get a look below, and discovered that room is built on 2 x 12” rough joists 16” OC.  But... why?  That seems incredibly overkill. The span is only 17’, and the room is 22 x 17.

Really I have two burning questions;

1) any theories on why the hell they would use 2x12’ lumber when putting up an addition on this one section?  It was previously a one-story living room before they added a ‘great-room’ above it

2) slightly more important:  Subfloor squeeks like hell, even though joists are rock-soil. So I decided to correct the problem.  Pulling up one 4x8’ sheet I found the following:  3/4” TNG plywood that was fastened with 3.5” framing nails and then (presumably later) also fastened with 1.5” drywall screws.  Many of the framing nails have popped.  My choice now seems to be either a) hammer down all the nail pops and possibly add new steel screws, or b) remove all the mishmash of fasteners, pull up each board and then re-lay the subfloor with proper steel flooring screws.

I’m guessing just hammering down the nail pops won’t be a lasting solution, but it’ll take several hours to pull up every framing nail they drove in there.

Thoughts?

Nail down the existing nails and add some screws to the sub floor. The 1.5" drywall screws aren't doing much. You could back them out and replace them with 2.5" wood screws or just add some extra screws. I typically glue and screw new sub floors.   

[FINate]

1) any theories on why the hell they would use 2x12’ lumber when putting up an addition on this one section?  It was previously a one-story living room before they added a ‘great-room’ above it

I'm having trouble visualizing the layout. Any chance the section in question was once a flat roof that then became the floor after an addition?

[BudgetSlasher]

As to question one. It is hard telling. Codes could have changed, that is what the builder could have been used to, it could have been designed for a higher live/dead load than the rest of the house (the modern tables I quickly looked at say you are at least 2x10 at 16" o.c. to get a 17' span @ 30 lb/ft2 live load), it could have been designed with lower deflections "L/###" to accommodate different flooring options, or it could have been something previously and that was what was already there.

As to question 2, I would drive the nails back down, and add in good quality screws (drywall screws are not very ductile and can snap, and structural screws are closer to nails in ductility. Since you already have nails for structural I would just use a good quality wood screw). I would go with at least 1-1/2" as I like screw to have at least 3/4" of bite (but I often exceed that). If I was laying the subfloor for the first time, or had it removed for some other reason, I would nail (for structural) polyurethane glue to the joist (kills squeaks) and screw (acts as clamps for the glue). You might be able to tell I can go a little overkill.

Also I see no need to remove the old fasteners Unless they are causing you issues. I am redoing a bathroom and after removing the tile I have found 1 layer of 5/8 ply nailed. I am going to drive the nail back down, add 3 in exterior (peace of mind in wet area) screws (I have lots left over from deck building), add a second later of 3/4 ply glue to the first and screwed with 1-3/8 exterior screws avoiding the joists. Then build by new floor on top of that. There are 3 structural supports in the bathroom; exterior wall, beam under the bathtub, and load bearing wall under the oppsitite wall of the exterior wall. (the room is 11 feet wide) And the whole house is framed in 2 x 12 for the floor joists.

[Papa bear]

I don’t find the joists to be that much overkill. I’d be much less excited if it was the other way with 2x8’s. So no big deal with over sizing. 

As for the floor? Screw it down with 2.5” construction screws. If you can pull all the subfloor up, then glue it down with some liquid nails first. 

If you have any duct work, that may end up squeaking too, so don’t expect perfection.


Sent from my iPhone using Tapatalk

[bacchi]

My 2nd floor also has 2x12s.

The engineer specified 2x10s but the framing crew ordered 2x12s by accident and didn't feel like swapping them.

[BudgetSlasher]

I don’t find the joists to be that much overkill. I’d be much less excited if it was the other way with 2x8’s. So no big deal with over sizing. 

As for the floor? Screw it down with 2.5” construction screws. If you can pull all the subfloor up, then glue it down with some liquid nails first. 

If you have any duct work, that may end up squeaking too, so don’t expect perfection.


Sent from my iPhone using Tapatalk

I much prefer PL 3x or 8x to liquid nails (really I prefer polyurethane to latex based).

[Papa bear]

I don’t find the joists to be that much overkill. I’d be much less excited if it was the other way with 2x8’s. So no big deal with over sizing. 

As for the floor? Screw it down with 2.5” construction screws. If you can pull all the subfloor up, then glue it down with some liquid nails first. 

If you have any duct work, that may end up squeaking too, so don’t expect perfection.


Sent from my iPhone using Tapatalk

I much prefer PL 3x or 8x to liquid nails (really I prefer polyurethane to latex based).

That works too. I use PL premium on projects.  I guess I’m not too brand specific.


Sent from my iPhone using Tapatalk

[nereo]

Thanks all for the responses. 

Update:  Going over the most recent plans the city has it seems likely what’s now the floor used to be a flat roof... so that might explain the 2x12”s.  I was just surprised more than anything because everything else in the home has been done very cheaply.

As most advised, I wound up hammering in the nail pops and then driving in new screws every 8” or so.  Damn that was a lot of screws for a ~350sqft floor...  me and my batteries are depleted.

One thing I found funny (and in a head-smacking sort of way) was that many of the screws that had been driven in - presumably to address the squeaking - were 1” #6 drywall screws.  **shocklingly** they didn’t so much in 3/4” ply, other than make a lot of screws to remove.  Probably 2-3lbs of them in total.

Floor is much quieter now.  No loud squeaks!  Even better it’s now all flush for the flooring, which will be luxury vinyl plank.

[Fishindude]

A general rule of thumb is that a floor joist at 16" centers spans and will carry floor loads at 1.5X it's depth dimension.
For instance a 2x4 spans 6', 2x6 spans 9', 2x8 spans 12', 2x10 spans 15', etc.
They used the correct joist size.

[nereo]

A general rule of thumb is that a floor joist at 16" centers spans and will carry floor loads at 1.5X it's depth dimension.
For instance a 2x4 spans 6', 2x6 spans 9', 2x8 spans 12', 2x10 spans 15', etc.
They used the correct joist size.

Thank you for that.

I guess what surprised me was the rest of the house uses 2x8" joists.... but everywhere else there's a center load-bearing wall in the middle, so there's never more than a ~10' span. 

[lthenderson]

Late to the game but I have found overkill to be quite common especially in older houses. I think there is a number of factors for that. Lumber was cheap, knowledge (span and load tables) was much scarcer and people just opted to go the easy route and make sure it was enough versus undersized. Like other said, I wouldn't worry about it and actually celebrate the fact that it is overkill.

I recently put new solid hardwood floors throughout the main floor of my house after pulling out the carpet and taking care of the very squeaky and uneven floor, much as you described. It was due to nails that has lost their hold and plywood that had curled up with time. I just used good quality screws about eight inches apart down every joist and it is solid as a rock now without a single squeak. I can actually sneak up on the kids now.

[nereo]

Late to the game but I have found overkill to be quite common especially in older houses. I think there is a number of factors for that. Lumber was cheap, knowledge (span and load tables) was much scarcer and people just opted to go the easy route and make sure it was enough versus undersized. Like other said, I wouldn't worry about it and actually celebrate the fact that it is overkill.

I recently put new solid hardwood floors throughout the main floor of my house after pulling out the carpet and taking care of the very squeaky and uneven floor, much as you described. It was due to nails that has lost their hold and plywood that had curled up with time. I just used good quality screws about eight inches apart down every joist and it is solid as a rock now without a single squeak. I can actually sneak up on the kids now.

Yes, but have you considered that you’ve also made it easier for them to sneak up on you (and also out without you hearing)?
:-P

[Dicey]

Late to the game but I have found overkill to be quite common especially in older houses. I think there is a number of factors for that. Lumber was cheap, knowledge (span and load tables) was much scarcer and people just opted to go the easy route and make sure it was enough versus undersized. Like other said, I wouldn't worry about it and actually celebrate the fact that it is overkill.

I recently put new solid hardwood floors throughout the main floor of my house after pulling out the carpet and taking care of the very squeaky and uneven floor, much as you described. It was due to nails that has lost their hold and plywood that had curled up with time. I just used good quality screws about eight inches apart down every joist and it is solid as a rock now without a single squeak. I can actually sneak up on the kids now.

Yes, but have you considered that you’ve also made it easier for them to sneak up on you (and also out without you hearing)?
:-P

I know the deed is done, but I'd have recommended pulling all the popped nails and replacing them with screws. Here's why: When you fill the room, the weight of the furniture will create squeaks in different places. You will be so pissed off disappointed that you did all that work and still end up with squeaks. # askmehow...

[NaN]

I opened this topic and was like "another structural question!" and am pleased at all the smart responses before this. The joists are the correct size.

At least you don't have 1/2" plywood subfloor.  I have that everywhere and all the floors squeak. I just live with it for now.

[BudgetSlasher]

I opened this topic and was like "another structural question!" and am pleased at all the smart responses before this. The joists are the correct size.

At least you don't have 1/2" plywood subfloor.  I have that everywhere and all the floors squeak. I just live with it for now.

I just screwed down the 5/8" subfloor in the bathroom I am redoing ... and in places it easily sucked the plywood down 1/8". Just the improved fasteners made a big difference.

3/4" ply and backerboard still to add.