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Old 04-16-2019, 03:43 PM   #1
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Bridging/Blocking between floor joists


Howdy everyone,

My house is built with 2 x 10's 16" on center. The span is 12 1/2'. The two spans are connected in the center with a double 2 x 10 that is bolted together and supported by 4 2 x 11 (1 1/2 x 9 1/2 actual) laminated and bolted header. There are 2 lally columns on the header so it has support every 8'.

The sub-floor is 5/8" OSB (I am hoping it is T&G). I have put 3/8" cdx plywood on top that was glued and screwed/stapled down prior to putting down 9/16" engineered hardwood.

There is no bridging/blocking between the joists. The floor is a bit bouncy. (Bottles jingle when you walk by).

I am hoping that putting some blocking between the joists will help stiffen it and prevent the slight bouncing.

My questions are:

Does the blocking need to go from sub-floor down or can it be partial? (there is hydronic heating attached to the sub-floor as well as cabling, plumbing, etc..)

What is the spacing for the blocking in the joist run? Is 4 feet okay in my 12+ foot run?

Does it have to be in a straight line or can I stagger it so I can nail it through the joist? Something like: --__--__ instead of ---------

Would the metal bracing that is nailed top and bottom work?

Thanks for all your recommendations.

Dan
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Old 04-16-2019, 04:11 PM   #2
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Re: Bridging/Blocking between floor joists


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Originally Posted by ktownskier View Post
Howdy everyone,

My house is built with 2 x 10's 16" on center. The span is 12 1/2'. The two spans are connected in the center with a double 2 x 10 that is bolted together and supported by 4 2 x 11 (1 1/2 x 9 1/2 actual) laminated and bolted header. There are 2 lally columns on the header so it has support every 8'.

The sub-floor is 5/8" OSB (I am hoping it is T&G). I have put 3/8" cdx plywood on top that was glued and screwed/stapled down prior to putting down 9/16" engineered hardwood.

There is no bridging/blocking between the joists. The floor is a bit bouncy. (Bottles jingle when you walk by).

I am hoping that putting some blocking between the joists will help stiffen it and prevent the slight bouncing.

My questions are:

Does the blocking need to go from sub-floor down or can it be partial? (there is hydronic heating attached to the sub-floor as well as cabling, plumbing, etc..)

What is the spacing for the blocking in the joist run? Is 4 feet okay in my 12+ foot run?

Does it have to be in a straight line or can I stagger it so I can nail it through the joist? Something like: --__--__ instead of ---------

Would the metal bracing that is nailed top and bottom work?

Thanks for all your recommendations.

Dan
There should not be more than 7 ft between bearing points or bridging, so you would want one in the centre, Putting 2 rows would not hurt.
A 2x4 on edge on the bottom is fine and some on the flat to get under pipes or ducts. And yes alternate sides of a line is fine for nailing.
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Old 04-16-2019, 04:32 PM   #3
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Re: Bridging/Blocking between floor joists


In any place where one style blocking, like solid blocks, doesn't fit well but cross blocking would, using either is fine. Sometimes the cross blocking leaves room for pipes and wires better than solid blocks. The key is, tying the movement of each joist to the other adjacent ones.

But don't expect the bounce to disappear. I'm sitting in a 13' x 16' room with 13' 2x10's that are cross blocked with two rows and my 14 pound dachshunds shakes the table when she rund across the floor. Not a lot, but she is tiny.

Bud
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Old 04-16-2019, 04:41 PM   #4
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Re: Bridging/Blocking between floor joists


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Originally Posted by Bud9051 View Post
In any place where one style blocking, like solid blocks, doesn't fit well but cross blocking would, using either is fine. Sometimes the cross blocking leaves room for pipes and wires better than solid blocks. The key is, tying the movement of each joist to the other adjacent ones.

But don't expect the bounce to disappear. I'm sitting in a 13' x 16' room with 13' 2x10's that are cross blocked with two rows and my 14 pound dachshunds shakes the table when she rund across the floor. Not a lot, but she is tiny.

Bud
There is another fix for that if your joists are still open below.
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Old 04-16-2019, 04:54 PM   #5
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Re: Bridging/Blocking between floor joists


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Originally Posted by Nealtw View Post
There is another fix for that if your joists are still open below.
What is it Neal?

And thanks for the answer!
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Old 04-16-2019, 04:57 PM   #6
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Re: Bridging/Blocking between floor joists


One thing I forgot to mention is that my home is a modular home. There are no joist hangers. The joists on the center are nailed through from the back. (or possibly screwed).

Would it help at all to put in some kind of joist connector? The joists are supported below so they are not hanging loose.
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Old 04-16-2019, 05:03 PM   #7
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Re: Bridging/Blocking between floor joists


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Originally Posted by ktownskier View Post
What is it Neal?

And thanks for the answer!

I haven't done it or seen it but an engineer told me about it.

You make an upside down T beam out of the joist by adding a 2x4 on the flat. He said to glue the center of the 2x4 and put it up first with a couple screws in the centre then wedge it up a little to add to the crown and screw off the 2x4 with a screw ever 6 inches.

A normal joist is under compression on the top and tension on the bottom.
The T makes the 2x4 also under compression and it works more like an arch.

It all sounds good but like I say, I have not seen it.
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Old 04-16-2019, 05:06 PM   #8
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Re: Bridging/Blocking between floor joists


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Originally Posted by ktownskier View Post
One thing I forgot to mention is that my home is a modular home. There are no joist hangers. The joists on the center are nailed through from the back. (or possibly screwed).

Would it help at all to put in some kind of joist connector? The joists are supported below so they are not hanging loose.
If they are on a wall or beam that is load bearing by 1 1/2" they are fine.
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