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Posted by marson on October 11, 2006, 9:02 am
i am about to start framing a superinsulated house. the specs call for
1/2" structural fiberboard sheathing (brace-rite by knight celotex).
no osb on the corners. this is not something i chose, but it is on
contract so i'm stuck with it. no additional bracing is required.
what do you engineers out there think of this system? i've heard of
houses which creak in the wind, but that was not the structural
fiberboard. there is no additional bracing specced.
anyone used this much? i'd really really like to sheath my walls
before standing them up, but am wondering if this is even possible with
this shit. for example, can you even walk on a wall, or will it break
between studs? can i cut it with a rotozip?
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Posted by PPS on October 13, 2006, 7:43 pm
It's listed as a permissible braced wall product in the IRC (method #4, 1/2"
or 25/32" structural fiberboard applied vertically or horizontally, on studs
spaced 16" o.c. maximum, and installed per table 602.3(1).
The kicker is it's only certified for 16" OC. [ R602.10.3 (4) ]
For a single story home in SDC (Seismic Design Category) A or B, 100 mph
wind or less, it's installed at each in and 25 feet oc (min. of 16% of the
wall). For SDC C or wind 110 mpg or less, it's 25% of the wall, for SCD D-1
it's 30% and for SCD D-2 it's 40% of the wall. ((Same as OSB)).
Fastening is 1-1/2" gal roofing nail, 6d common nail (8d if structurally
rated) or staple 16 ga. 1-1/2". All fastening is 6" oc field and 3" oc.
edge. (man that's a lot of nails.)
Advantages appear to be high permeability rating of 20 and an R-value of 1.3
(yawn). It appears to be ok for up to a 3-story home, <110 mph wind, and
seismic category D-2 or less.
Restrictions stated are; "Knight-Celotex Fiberboard products must not be
used in close proximity to chimneys, heater units, fireplaces, steam pipes
or other surfaces which could provide long term exposure to excessive heat
(maximum 212*F) without adequate thermal protection. Consult the appropriate
heating appliance manufacturer's instructions before installation."
The Modulus of Rupture, is 400 psi min.
Water Absorption for 24 hrs. is 15% max.
Tensile Strength (perpendicular to surface) : 800 psi
Warnings are: "Provide proper ventilation and use of respiratory protection
as required by the manufacturer. Avoid dust inhalation. Use caution when
creating large amounts of dust because of potential
explosion hazard. Refer to manufacturer's MSDS data for these and other
precautions." "Panels must be installed vertically."
Installation instructions include: "It is recommended that the exterior
finish be applied within 30 days. If applied sheathing should get wet, wait
until completely dry before application of exterior finish."
In looking at the ICC Evaluation report ESR-1978, conditions for use state
that: (5.1) it is not to be used as a nailing base for finish siding. (5.2)
it's limited to type V-B construction and IRC structures. (5.4) if installed
on exterior side of exterior wall, must be protected a water-resistive
barrier. (Product information requires this to be done within 30 days.)
Keep in mind that the stuff will not qualify as fire blocking (if that
applies).
My **guess** in looking at the spec's is, you can walk on the sheathing
without rupture.
Personally I would have specified 24" oc studs to gain more R-value, and
OSB. (But that's opinion only.)
>i am about to start framing a superinsulated house. the specs call for
> 1/2" structural fiberboard sheathing (brace-rite by knight celotex).
> no osb on the corners. this is not something i chose, but it is on
> contract so i'm stuck with it. no additional bracing is required.
>
> what do you engineers out there think of this system? i've heard of
> houses which creak in the wind, but that was not the structural
> fiberboard. there is no additional bracing specced.
>
> anyone used this much? i'd really really like to sheath my walls
> before standing them up, but am wondering if this is even possible with
> this shit. for example, can you even walk on a wall, or will it break
> between studs? can i cut it with a rotozip?
>
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Posted by Bob Morrison on October 14, 2006, 2:27 pm
In a previous post PPS wrote...
> > what do you engineers out there think of this system? i've heard of
> > houses which creak in the wind, but that was not the structural
> > fiberboard. there is no additional bracing specced.
>
You could always use OSB or plywood over the fiberboard.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
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Posted by RicodJour on October 14, 2006, 8:27 pm
Bob Morrison wrote:
> In a previous post PPS wrote...
> > > what do you engineers out there think of this system? i've heard of
> > > houses which creak in the wind, but that was not the structural
> > > fiberboard. there is no additional bracing specced.
> >
>
> You could always use OSB or plywood over the fiberboard.
That's a big expense to cover a building twice - who's supposed to pay
for it? If you're talking about just adding the OSB over the
fiberboard on the corners, that's going to cause an issue with the
siding surface. Please clarify, Bob.
R
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Posted by marson on October 15, 2006, 9:35 pm
RicodJour wrote:
> Bob Morrison wrote:
> > In a previous post PPS wrote...
> > > > what do you engineers out there think of this system? i've heard of
> > > > houses which creak in the wind, but that was not the structural
> > > > fiberboard. there is no additional bracing specced.
> > >
> >
> > You could always use OSB or plywood over the fiberboard.
>
> That's a big expense to cover a building twice - who's supposed to pay
> for it? If you're talking about just adding the OSB over the
> fiberboard on the corners, that's going to cause an issue with the
> siding surface. Please clarify, Bob.
>
one of the reasons they are calling for fiberboard is because of its
high perm rating. so adding OSB would defeat that purpose.
my main concern is that it provides enough rigidity. after all, this
is a half million dollar project, and here we are using a product that
is regarded by many as inferior to OSB. well, I guess i'll find out.
thanks for the replies.
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