installing 3' knee wall
bitternut
centers and the roof pitch is 12/12. I am insulating with R-38 batts. To
make insulating easier I was planning on using a bottom 2x4 plate and
cutting the top ends of the knee wall studs at a 45 so they could be nailed
flush with the edge of the rafters. Would this be the way to do it or should
I lap the knee wall studs onto the sides of my rafters? The total span of
the attic roof is 24'. I would be using a framing nailer.
willshak
typed the following:
I would nail the studs to the sides of the rafters. You don't have to
worry about the exact height of each stud's 45º cuts, and the framing
nailer is less likely to bang the studs out of plumb.
--
Bill
JerryD(upstateNY)
amount of crown in them so if you are going to drywall the ceiling, it will
be up and down where it meets the knee wall.
If you are just leaving the rafters exposed, you will never see the up and
down of the rafters.
If you are going to drywall it and want it to look nice, you should nail a
top plate to the bottom of the rafters and fasten the studs to the plate.
When you snap a chalkline across the bottom of the rafters, for the plate
line, you might have to put a temporary stud under one or more rafters that
are much lower than the rest.
Don't forget that the line you snap will be ?' or so down the rafter from
what the inside wall line will be.
Most important...........don't forget to use Styrofoam spacers between the
rafters to keep the insulation down from the roof you get air circulation.
Without the airspace, the roof will rot.
--
JerryD(upstateNY)
Jim
birdmouth to allow for the kneewall in the rafters locks all in place. Not
as dependent on nails for rigidity for the roof frame structure as a whole.
Does take more time, patience, and finesse this way.
--
Lil' Dave
Beware the rule quoters, the corp mindset, the Borg
Else you will be absorbed
"bitternut" <bitt...@adelphia.net> wrote in message
news:sq-dnYjiBIQN3u7e...@adelphia.com...
RicodJour
> I wouldn't. Its more difficult to keep the knee wall straight. Cutting a
> birdmouth to allow for the kneewall in the rafters locks all in place. Not
> as dependent on nails for rigidity for the roof frame structure as a whole.
> Does take more time, patience, and finesse this way.
And it also compromises the rafters. The idea is to not have the
kneewall pick up any of the rafter loading and transfer it to the
floor/ceiling below. Rafters move with wind and snow loading - that
will translate into cracks in the ceiling below the kneewall. It's
better to build the kneewall freestanding and attach it to the rafters
with some clips made from some steel stud scrap to allow the rafters to
move.
R
Bob Morrison
> And it also compromises the rafters. The idea is to not have the
> kneewall pick up any of the rafter loading and transfer it to the
> floor/ceiling below. Rafters move with wind and snow loading - that
> will translate into cracks in the ceiling below the kneewall. It's
> better to build the kneewall freestanding and attach it to the rafters
> with some clips made from some steel stud scrap to allow the rafters to
> move.
>
As usual, Rico has given an excellent recommendation.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bitternut
make a difference. The plans show a birdsmouth in the rafters and no use of
a top plate on the knee wall. The floor that the knee wall sits on is tongue
and groove 3/4" plywood glued and nailed to 11-7/8" I-joists. The joists are
on 24" centers. The plans also have an engineer's stamp. I would prefer to
not cut a birdsmouth in the rafters since I would assume that would weaken
the rafters. I have already installed Styrofoam baffles against the roof
sheathing. for ventilation. The house is located in New York State which may
also affect someone's opinion. I kind of like the idea of making the wall
free standing and then attaching it to the rafters with brackets. Would most
likely be the easiest to accomplish. I just was wondering if the knee wall
was supposed to act like part of a truss in some sense. Since the wall is
only 3' high and also 3' from the edge of the exterior walls would there
really be enough flexing to cause dry wall cracks? We have had some pretty
strong winds and things seem pretty solid without the knee wall so maybe it
is not needed for strength. Of course the attic is not loaded up yet and
there is no drywall on the attic ceiling yet.
"bitternut" <bitt...@adelphia.net> wrote in message
news:sq-dnYjiBIQN3u7e...@adelphia.com...
Bobk207
at first it seemed like the knee wall was being added to an existing
structure, that is was just a simple partition to change the attic.
if that is the case then Rico's free standing suggesetion makes the
most sense.
Now you're talking about plans & what appears to be an engineered
design.
Only the designer knows if the wall is supposed to "act as part of a
truss"
IMO bring any part of the roof load into the attic floor (& thus into
the ceiling below) doesn't sound like a great idea
just what parts of this project are "existing" and what parts are
'new"
Did the engineered plans cover all the attic mods including the drywall
which is being added to the bottom side of the roof rafters?
cheers
Bob
bitternut
new 12/12 pitch roof replaced it. Everything from the first floor walls top
plate up is new construction. The plans call for 1/2" drywall on all
interior walls and the ceiling. The ceiling collar ties are 2x6 placed at 8'
height. Will end up with a room 18' x 40'.
"Bobk207" <rkaz...@gmail.com> wrote in message
news:1131670388.2...@g49g2000cwa.googlegroups.com...
Jim
would probably work. Originally, I was under the impression the knee wall
was some load bearing wall. But, since you're relying on engineered plans,
follow those to the letter.
--
Lil' Dave
Beware the rule quoters, the corp mindset, the Borg
Else you will be absorbed
"bitternut" <bitt...@adelphia.net> wrote in message
news:E7qdnQ7wZdN...@adelphia.com...
willshak
the following:
> On Thu, 10 Nov 2005 08:24:50 -0500, willshak <will...@oohvc.rr.com>
> wrote:
>
>
>> On 11/10/2005 7:56 AM US(ET), bitternut took fingers to keyboard, and
>> typed the following:
>>
>>> I will be installing a 3' knee wall in my attic. The rafters are 2x12 on 16"
>>> centers and the roof pitch is 12/12. I am insulating with R-38 batts. To
>>> make insulating easier I was planning on using a bottom 2x4 plate and
>>> cutting the top ends of the knee wall studs at a 45 so they could be nailed
>>> flush with the edge of the rafters. Would this be the way to do it or should
>>> I lap the knee wall studs onto the sides of my rafters? The total span of
>>> the attic roof is 24'. I would be using a framing nailer.
>>>
>> I would nail the studs to the sides of the rafters. You don't have to
>>
>
> inspector will call it out every time.
>
I may be misinterpreting what the OP is trying to do, but I had assumed
that he is building a non-bearing wall between the joists and the
rafters in order to apply sheetrock or other material to build an
enclosed living space, as in this image:
http://tinyurl.com/dd5km
--
Bill
RicodJour
> On 11/10/2005 10:22 PM US(ET), TimL took fingers to keyboard, and typed
> the following:
> > On Thu, 10 Nov 2005 08:24:50 -0500, willshak <will...@oohvc.rr.com>
> > wrote:
> >
> >
> >> On 11/10/2005 7:56 AM US(ET), bitternut took fingers to keyboard, and
> >> typed the following:
> >>
> >>> I will be installing a 3' knee wall in my attic. The rafters are 2x12 on 16"
> >>> centers and the roof pitch is 12/12. I am insulating with R-38 batts. To
> >>> make insulating easier I was planning on using a bottom 2x4 plate and
> >>> cutting the top ends of the knee wall studs at a 45 so they could be nailed
> >>> flush with the edge of the rafters. Would this be the way to do it or should
> >>> I lap the knee wall studs onto the sides of my rafters? The total span of
> >>> the attic roof is 24'. I would be using a framing nailer.
> >>>
> >> I would nail the studs to the sides of the rafters. You don't have to
> >> nailer is less likely to bang the studs out of plumb.
> >>
> >
> > That won't pass building codes. Least not is Houston and a home
> > inspector will call it out every time.
> >
> I may be misinterpreting what the OP is trying to do, but I had assumed
> that he is building a non-bearing wall between the joists and the
> rafters in order to apply sheetrock or other material to build an
> enclosed living space, as in this image:
> http://tinyurl.com/dd5km
The picture that shows the knee wall framing is perfect. That shows
the metal clips that are attached to the sides of the rafters that
brace the kneewall studs. The clips don't support the rafters in any
way so there will be no transfer of roof load to the kneewall and
floor.
R
bitternut
only difference is that my roof pitch is 12/12 and I used Andersen venting
roof windows instead of dormers. Now if I can find some of those framing
clips. I have checked with the standard box stores and have not found
anything that appears to be dedicated for my purpose. Guess I will have to
use my imagination with what is available.
"RicodJour" <rico...@worldemail.com> wrote in message
news:1131713559.6...@f14g2000cwb.googlegroups.com...
Bobk207
http://www.strongtie.com/products/connectors/STC-STCT-DTC_PT.html
If you build your partition wall with a top plate, this family of clip
is meant to control the top of the partition wall w/o allowing
vertical load transfer between the roof structure & the wall.
Again I am somewhat reluctant to suggest changes to the engineered
plans but they seem lacking.
cheers
Bob
stealth
> Bob..........An existing low pitched roof was removed from my house and a
> new 12/12 pitch roof replaced it. Everything from the first floor walls
> top plate up is new construction. The plans call for 1/2" drywall on all
> interior walls and the ceiling. The ceiling collar ties are 2x6 placed at
> 8' height. Will end up with a room 18' x 40'.
The answers you have received are indeed correct, but the correct answer
isn't always the right answer. If the engineered project is completed with
the roof currently standing on its own merit, and the only purpose of the
knee wall is for finishing out the area, then it is a none-bearing wall,
period. If properly installed, any deflection/additional loading from the
2" X 12" rafters covered in OBS/plywood with a bottom strap is going to be
quite minimal and not for concern.
Assuming you would not be removing/altering any roof bracing that may be
already in place, I agree with the bird-mouth cutout method, as it will
provide the straightest and most secure wall and is a common building
practice. As for any structural compromising of the rafters, that is more
than offset with the support of the knee-wall, which by the way, would be
distributing any roof load it may gain over several floor joists. IOW, you
are not creating any point loads, and the truth be known, the knee-wall
would place less stress on the floor than a heavy couch or pool table or
human walking. Furthermore, the floor load most likely already exceeds the
roof load per specs, with even distribution versus point loads being the key
here. As a side note, the bird-mouth does not need to be cut out more than
2" for this type of install.
Personally, unless there is something that has not been addressed here
already, the simplest method for a DIY would be to build the knee-wall
laying down on the floor using both bottom and top plates, and then stand
the finished wall up and against the rafters. Once in place, stand a beveled
2" X4" on edge on top of the top plate to fill in the resulting gap from
top-plate and rafter. Use a chalk line to keep the wall straight and even
at the rafters, and note you will need to build the wall 3 1/2" shorter than
the finished wall height to allow for the inner/outer differences (thickness
of the wall against 12/12 pitch). The filler board on top will bring the
wall up to the finished height.
In summary, a quick visit to the engineer that drew the plans would be in
order if you have any doubts.
Hope this helps.
s