DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Flooring > Flooring - 24 OC joists

Help Support House Repair Talk by donating using the link above.
Thread Tools Search this Thread
Old 02-19-2010, 12:52 PM  
Junior Member
Join Date: Jan 2010
Posts: 6

Sorry for the delayed reply - busy month

Thanks, Wuzzat, for all the info!

After thinking about this for the past month, I would really like to spearhead adding joists...

As I said, I do have construction experience; however, I have only installed floor joist on new builds / additions.

I said in a previous post that I would LIKE to add the joist without ripping up the subfloor (and damaging the existing flanges). I would like to position each joist laying on its side where it's going to go (in the centers - not sister joist), add glue on the flange, then beat the joist upright into place, then someone on top will screw down via chalk lines.

This may be a long shot, but is there anyone out there that has done this? CAN it be done?

Furthermore, Would this help to make the floor feel more solid? Would it be worth the money / effort? The floor is not 'bouncy' per se - but it would be nice to stiffen the floor (as well as close the 24" gap before installing the new tile / hardwoods)

Thanks again.

aaronled is offline  
Reply With Quote
Old 02-19-2010, 01:49 PM  
Join Date: Jan 2010
Location: , Western Hemisphere, N of the equator
Posts: 2,471
Liked 176 Times on 162 Posts
Likes Given: 108


Originally Posted by aaronled View Post
I would like to position each joist laying on its side where it's going to go (in the centers - not sister joist)
If your current deflection is L/360, what deflection would you like to have? L/480?

From the deflection design goal, the joist size [this gives I, the moment] and material [this gives E, the modulus of elasticity] can be figured.

But since I = b(h^3)/12, increasing h [height] by 10% gives a 33% increase in moment [(1.1)^3 = 1.33], but increasing b [width] by 10% gives only a 10% increase in moment.
That's why joists are on edge. It's the best use of the material for the money spent.

In your case you might do better running small steel I beams down the middle between the joists. I have a list of moments and E values for various types of steel I beams.

Or, if you can find a way to fasten a 2x under each existing joist to increase its height and therefore its I, you can dial up however much stiffness you want, at a loss of some headroom.

Last edited by Wuzzat?; 02-20-2010 at 01:52 PM.
Wuzzat? is offline  
Reply With Quote
Old 02-22-2010, 10:43 AM  
Junior Member
Join Date: Jan 2010
Posts: 6

I think what I wrote may have been taken out of context. Yes, I would like to lay the joist down on their sides in between the existing joist - BUT THEN, they would be stood on edge like the existing ones (the laying down on the side bit was just to convey the gluing and installing method.) The end result would be just like the existing joist - only now they would be 12oc instead of 24oc. I was trying to paint a picture of how I would go about it - sorry if it is confusing or not coming out right!

Having said that - your suggestion about the small steel beams sounds interesting. This makes me very curious - as it SEEMS it would be an easier way to install (could be visualizing it wrong though!) This might be worth looking into seeing if it's a viable, price for materials, etc...

The BIGGEST goal here is to provide a nice flat (without dipping) sub for new floors - however, if I can increase the L value, then that would be great too! As another poster pointed out, i could just beef up the sub-ply by adding more sheets...however, I'm not so keen on this idea being that it would seem to add a lot of extra weight on an already questionable deflection rating... Again, the basement is not finished yet (but soon will be) - and I think now would be the time to move on this (if I do)!
aaronled is offline  
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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

Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
not enough floor joists shedee Framing and Foundation 2 08-16-2013 04:32 PM
Joists cmerk16 Walls and Ceilings 7 03-28-2012 06:22 PM
help with joists britny1 Carpentry and Woodworking 2 10-14-2010 06:55 PM
4x8 joists in my woodshed camb General Home Improvement Discussion 2 09-01-2010 07:07 PM
Strengthening joists spooksmcgee Flooring 6 05-25-2008 01:49 PM

Newest Threads