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-   -   Effect of bridging 2"x10", 14' span joists (http://www.diychatroom.com/f19/effect-bridging-2-x10-14-span-joists-97925/)

BMS98 03-10-2011 12:16 PM

Effect of bridging 2"x10", 14' span joists
 
I did a search and found lots of posts on how to install the bridging, but none really discussed what the result typically is in stiffness, say, percentage-wise.

I've got a middle level floor with 2"x10" joists, spanning 14'. 5/8" T&G plyood on top, glued and screwed. Installed 3/4" T&G wood floors and am getting some movement/creaks. Want to install blocking to try to stiffen up the floor, but am curious if there, again, is a factor of stiffness that can be expected. Blocking will be 2"x10" solid, not x-bracing, except where I have to go around a duct or pipe. Planning on 2 rows of bridging, evenly spaced.

Ron6519 03-10-2011 01:08 PM

Quote:

Originally Posted by BMS98 (Post 606711)
I did a search and found lots of posts on how to install the bridging, but none really discussed what the result typically is in stiffness, say, percentage-wise.

I've got a middle level floor with 2"x10" joists, spanning 14'. 5/8" T&G plyood on top, glued and screwed. Installed 3/4" T&G wood floors and am getting some movement/creaks. Want to install blocking to try to stiffen up the floor, but am curious if there, again, is a factor of stiffness that can be expected. Blocking will be 2"x10" solid, not x-bracing, except where I have to go around a duct or pipe. Planning on 2 rows of bridging, evenly spaced.

That size joist spanning 14 feet shouldn't be the issue. What sort of movement are you getting? And what's going on at the time of this movement?
Are you sure it's not the T&G flooring?
When and how was it installed?
Ron

BMS98 03-10-2011 02:44 PM

Installed 3-1/2" x 3/4" T&G wood floor (tigerwood) about a month ago. Nailed it every 8" and into the joists with 2" L-cleats/pneumatic nailer. 3/4" spacing all around. Humidity in the house is between 30%-35% with our whole house humidifier in. Reason I think it is the joists moving is when you step into the room onto the wood, you can hear the floor "crackling" at the other end of the room on the same joist. It's not just where you step. As you walk around, you can hear it all move as a unit. Once you've walked on it for a minute, it completely goes away which I realize would make you think it isn't joist movement or it would keep happening, but I think that is just the wood not making noise because it has already rubbed together. It is still moving.

SIHUNTER 03-10-2011 02:56 PM

Was felt paper laid down prior to installing the Tigerwood? If not, the wood to wood contact of the subfloor to the Tigerwood could be some, if not all of the cause of your problem.

BMS98 03-10-2011 03:35 PM

put down red rosin paper.

Ron6519 03-10-2011 03:40 PM

What species of lumber are the joists made of? I think SPF joists have more bounce then Doug fir.
Ron

BMS98 03-10-2011 08:55 PM

not sure. the ones I bought to sister up to a couple of sagging / crowned ones are douglas fir. They look an awful lot like pine.

Ron6519 03-10-2011 10:23 PM

Quote:

Originally Posted by BMS98 (Post 607029)
not sure. the ones I bought to sister up to a couple of sagging / crowned ones are douglas fir. They look an awful lot like pine.

The joists should have a lumber stamp that identifies the grade and species. The joists should be graded #2 or better. Lower grades, less span length and more bounce.
Ron

loneframer 03-11-2011 06:50 AM

Bridging will help by unifying the floor and forcing the joists to share concentrated load, such as someone walking across the floor.

The key is to make sure it is absolutely tight, including the bay that is over the foundation or supporting wall. This is hard to accomplish with blocking, due to inconsistency in the joists, such as cupping. For best results, the path should be uninterrupted from end to end.


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