leveling floor joists with 2x4s.....

Reply

  #1  
Old 03-01-11, 06:39 AM
Member
Thread Starter
Join Date: Oct 2008
Location: NYC
Posts: 433
leveling floor joists with 2x4s.....

I will be installing a Bruce pre-finished wood flooring in my bedroom and I am thinking of leveling the 60 year old 3"x12" 16" on center 23' span joists so that I can install the 2 - 3/4 cdx sheet plywood subfloor on before the wood flooring goes in.
I was thinking of nailing/screwing 2x4s on to the sides of the 3x12s where needed for leveling purposes.
The floor is not sagging, but there is a small difference from joist to joist, I would say no more than 1/8 to 1/4" or 5/8" to 1" total in a 12 foot span.
I thought that nailing the 2x4s with 3" nails every 6"-10" would do.
Any comments come appreciated.
 

Last edited by zizanio; 03-01-11 at 08:49 AM.
Sponsored Links
  #2  
Old 03-02-11, 06:59 AM
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,986
I don't think it's necessary. The plywood is flexible enough.
 
  #3  
Old 03-03-11, 12:14 PM
Member
Thread Starter
Join Date: Oct 2008
Location: NYC
Posts: 433
Originally Posted by Pulpo View Post
I don't think it's necessary. The plywood is flexible enough.

Thanks Pulpo. The plywood is probably flexible enough you're right, but the money was burning a hole in my pocket so I went out and bought 40 2x4s and a box of nails and did it so that I wouldnt have to say "I should have" after I close it up.
Thanks again
 
  #4  
Old 03-03-11, 02:58 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,968
If you're sistering all those 2x4's to the existing joists, your underlayment seams will be offset and you need to bolt all the sisters to the existing joists. Nailing is not sufficient. Sorry to be the bearer of such news. Applying the plywood to the existing joists would have been fine, and if you needed, you could have floated the difference out.
 
  #5  
Old 03-04-11, 03:33 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,968
Afterthought. I would not use 2x4's for sisters, anyway. They must be of a dimension that will take the full weight of the floor, probably 2x10 in your case.
 
  #6  
Old 03-05-11, 04:04 PM
Member
Join Date: Mar 2009
Location: WA
Posts: 1,167
Never heard that before, where did you get your information? A 10d (3") framing nail with 1-1/2" into the joist from the side will hold 120# shear.Attach the 2x4 every 2' nail spacing will give you 60# of shear, spaced 16" o.c., no worries at all.....depends on the joist spacing for the 40# per sq. ft. Common wire nails

Gary
 
  #7  
Old 03-05-11, 04:40 PM
Member
Join Date: Mar 2011
Location: canada
Posts: 22
This is a bedroom so i believe this would work for you.Myself i would have used glue and screws.If you drive your spike the right way...on an angle..would help.Again.your bedroom, not subject to pianos or fridge..,etc. You may wanna double up on the spikes around the bed posts if ...ya know...lol..
 
  #8  
Old 03-06-11, 05:59 AM
Member
Join Date: Aug 2009
Location: USA
Posts: 4,941
I saw this done on This Old House not too long ago. I believe Tom Silva used nails an construction adhesive. I think the most the 2x4 stuck above was about 3/4" in his situation.

This isn't my area of expertise, but I don't see much trouble with it. If for some reason it becomes problematic in the future, I think it wouldn't be too difficult to shore up. You can add screws, some lags and even put a larger board underneath the 2x4 and glue and bolt that to the old beam.
 
  #9  
Old 03-06-11, 10:00 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,968
My exact point, drooplug, why take a chance to having a failure when it can be done sufficiently to stay in the first place. Gary, you bring up a good reference, but I still don't like nails alone to hold up sistered boards that will carry the entire weight of what was a much wider and thicker board. The nails may be advertised as having a certain sheer strength, and I praise the Chinese for their intuitiveness, but not to hold up a critical part of a house. I think the OP will have to make a decision, and go with it. Hopefully not on the fact he already bought 40 2x4's.
 
  #10  
Old 03-06-11, 12:11 PM
Member
Join Date: Jan 2011
Location: USA
Posts: 4,183
I also would never have used 2 X 4's,way to narrow and will tend to twist and cause squecks.
I also would never have used CDX as a subflooring. It's not even subfloor rated.
Subfloor rated would be 0 voids in the core. CDX is full of holes and should only be used for roof and wall sheathing.
Advantec T&G should have been used.
 
  #11  
Old 03-06-11, 03:28 PM
Member
Join Date: Mar 2009
Location: WA
Posts: 1,167
The 2x4's are not spanning to hold up the load as a joist would. The 3x12's are carrying the load. Loads are transmitted straight down from above through the nails to the carrying joists. Span does not figure into the equation here, 2x4 or 2x6 wouldn't make a difference---- no span involved. It's the nail spacing that carries the load. And the 2x4 is not carrying "the entire floor" only the load above the nail.

Worried about twisting wood---- don't buy from the box stores.

Good point on the t&g though, or blocking is required; APA Blog for Professional Associates: Proper Orientation of Plywood Underlayment in Floor Systems

Gary
 
  #12  
Old 03-15-11, 03:19 PM
Member
Thread Starter
Join Date: Oct 2008
Location: NYC
Posts: 433
Well guys, thanks for the comments. I decided to go with it as I originally posted. I must say, the job came out nice, I will post here if I see anything in time.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes