New house Louisana Pacific I beams too far apart

Posted by Bobk207 on December 31, 2008, 12:27 pm

On Dec 30, 7:23=A0am, laco...@gmail.com wrote:

> This house is about 2 years old now. Two story house on a unfinished
> basement. There is a lot of noise from the walls and subfloor (creaks
> and pops) when walking on it. I carefully screwed down the subfloor to
> the LP wooden I-beams, but this makes no difference since the 3/4 OSB
> that makes up the subfloor is sitting across I-beams that are 24" OC
> apart. I can visibly see the OSB flexing when stepping in gap b/w the
> I-beams. The OSB is 4x8' sheet tounge and groove on the 8' side. The
> span of the unsupported beam is about 19' with the longest beam being
> 29'.
> 24" seems a bit much to prevent minor floor noise. I am wondering what
> can be done to make the floor as quiet as possible. My solution up
> until now is to take up the OSB and install "struts" between the I-
> beams, but I am not sure how the strut should be constructed and how
> far apart they should be. Thanks for your suggestions!
> Chris

Chris-

I-joists at 24" o/c is allowable but imo, a little on the optomistic
side. :(

How deep are you I-joists? you mention an average span of 19' and
longest span of 29'?

Wooden floors can be quite noisy, esp when over an unfinished
basement. You mention visible movement but can you associate the
visible movement with noise?

Before you go through the work & expense of............

adding blocking or another layer of sheathing or removing and
replacing sheathing with thicker T&G plywood

be sure you really have determined the source(s) of the
noise......otherwise all the work will be wasted.

LP has blocking designs, you can use rim board or I-joists. They both
need to be cut to fit. I would suggest not using sawn lumber, use
"engineered" lumber.

Blocking could be added from below w/o having to R&R the current
sheathing but it would rather tediuous.

cheers
Bob

Posted by tbasc@bellsouth.net on December 31, 2008, 2:02 pm

On Dec 30, 10:23=A0am, laco...@gmail.com wrote:

Most of the info posted in reply is good as far as it goes.
However, since you note "a lot of noise from the walls and
subfloor ...", Iwould, if it were my house, invest in a forensic
engineer or architect to investigate the entire frame. This on the
theory that 'nose' suggests movement and movement suggest structural
problems.
T

Posted by Voyager on January 2, 2009, 1:30 pm

tbasc@bellsouth.net wrote:

> On Dec 30, 10:23 am, laco...@gmail.com wrote:

>> This house is about 2 years old now. Two story house on a unfinished
>> basement. There is a lot of noise from the walls and subfloor (creaks
>> and pops) when walking on it. I carefully screwed down the subfloor to
>> the LP wooden I-beams, but this makes no difference since the 3/4 OSB
>> that makes up the subfloor is sitting across I-beams that are 24" OC
>> apart. I can visibly see the OSB flexing when stepping in gap b/w the
>> I-beams. The OSB is 4x8' sheet tounge and groove on the 8' side. The
>> span of the unsupported beam is about 19' with the longest beam being
>> 29'.
>> 24" seems a bit much to prevent minor floor noise. I am wondering what
>> can be done to make the floor as quiet as possible. My solution up
>> until now is to take up the OSB and install "struts" between the I-
>> beams, but I am not sure how the strut should be constructed and how
>> far apart they should be. Thanks for your suggestions!
>> Chris

>
> Most of the info posted in reply is good as far as it goes.
> However, since you note "a lot of noise from the walls and
> subfloor ...", Iwould, if it were my house, invest in a forensic
> engineer or architect to investigate the entire frame. This on the
> theory that 'nose' suggests movement and movement suggest structural
> problems.
> T

Not at all. ALL structures move (deflect) under load. Deflection
limits are one of the design criterion and typical residential floors
are designed for deflection up to L/360 at maximum allowable load. So,
for the 19' span listed above, a deflection of up to 5/8" is acceptable
for most building codes. Movement does not at all correlate to a
structural problem. It may be an annoyance, but that is far different
from being a structural problem.

Often the issue isn't the deflection itself, but the damping of the
floor structure. A heavier floor often "feels" much better even if it
has the same or even greater deflection as compared to a lighter floor.
The reason is that the dynamics from someone walking across the floor
can be quite different.

Matt

Posted by Bobk207 on January 3, 2009, 2:31 am

> tb...@bellsouth.net wrote:

> > On Dec 30, 10:23 am, laco...@gmail.com wrote:

> >> This house is about 2 years old now. Two story house on a unfinished
> >> basement. There is a lot of noise from the walls and subfloor (creaks
> >> and pops) when walking on it. I carefully screwed down the subfloor to
> >> the LP wooden I-beams, but this makes no difference since the 3/4 OSB
> >> that makes up the subfloor is sitting across I-beams that are 24" OC
> >> apart. I can visibly see the OSB flexing when stepping in gap b/w the
> >> I-beams. The OSB is 4x8' sheet tounge and groove on the 8' side. The
> >> span of the unsupported beam is about 19' with the longest beam being
> >> 29'.
> >> 24" seems a bit much to prevent minor floor noise. I am wondering what
> >> can be done to make the floor as quiet as possible. My solution up
> >> until now is to take up the OSB and install "struts" between the I-
> >> beams, but I am not sure how the strut should be constructed and how
> >> far apart they should be. Thanks for your suggestions!
> >> Chris

> > Most of the info posted in reply is good as far as it goes.
> > However, since you note "a lot of noise from the walls and
> > subfloor ...", Iwould, if it were my house, invest in a forensic
> > engineer or architect to investigate the entire frame. This on the
> > theory that 'nose' suggests movement and movement suggest structural
> > problems.
> > T

> Not at all. =A0ALL structures move (deflect) under load. =A0Deflection
> limits are one of the design criterion and typical residential floors
> are designed for deflection up to L/360 at maximum allowable load. =A0So,
> for the 19' span listed above, a deflection of up to 5/8" is acceptable
> for most building codes. =A0Movement does not at all correlate to a
> structural problem. =A0It may be an annoyance, but that is far different
> from being a structural problem.
> Often the issue isn't the deflection itself, but the damping of the
> floor structure. =A0A heavier floor often "feels" much better even if it
> has the same or even greater deflection as compared to a lighter floor.
> =A0 The reason is that the dynamics from someone walking across the floor
> can be quite different.
> Matt

Chris-

Matt's comment

>>>>"Movement does not at all correlate to a

structural problem. It may be an annoyance, but that is far different
from being a structural problem. "<<<<

is right on the money.

Noise / deflection / springiness is annoying but usually nothign
more. :(

Depending on how serious you are about eliminating (reducing) the
noise, I would suggest getting an engineer experienced in floor
diaphragm dynamics out to take a listen.

cheers
Bob

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New house Louisana Pacific I beams too far apart - Page 2