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Posted by Alan on August 4, 2006, 10:00 pm
I provided a truss company the basics of my present garage, so that
they could design a new roof for it. I told them I have 18"D by 15"W
perimeter foundation, which is suitable for support of two story house
in my county. I also told them that I have 16" OC 2x4 stud walls with
double top plate, also capable of supporting a second story by code.
Some of this information was provided in drawings and other by e-mail.
The computer techie designer spent a lot of time with me on a truss
system, I put half down and got engineered stamped calculations. When
I managed to have a presubmisson review by the senior architect at the
planning department, he told me that the point load for two multiply
trusses, which support the ladder of joists supporting dormers and a
deck, exceed the point load capability of the foundation. Can anybody
tell me how to calculate what point load my foundation can take? Also,
need help considering possibilities, other than the big hassle of
jackhammering, digging, and pouring more concrete and rebar into an
otherwise good foundation. I want the dormers and the patio deck. Can
I spread the load from these trusses to adjacent trusses for example?
Ideas wanted before I deal with the truss company again.
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Posted by RicodJour on August 4, 2006, 10:32 pm
Alan wrote:
> I provided a truss company the basics of my present garage, so that
> they could design a new roof for it. I told them I have 18"D by 15"W
> perimeter foundation, which is suitable for support of two story house
> in my county. I also told them that I have 16" OC 2x4 stud walls with
> double top plate, also capable of supporting a second story by code.
> Some of this information was provided in drawings and other by e-mail.
> The computer techie designer spent a lot of time with me on a truss
> system, I put half down and got engineered stamped calculations. When
> I managed to have a presubmisson review by the senior architect at the
> planning department, he told me that the point load for two multiply
> trusses, which support the ladder of joists supporting dormers and a
> deck, exceed the point load capability of the foundation. Can anybody
> tell me how to calculate what point load my foundation can take? Also,
> need help considering possibilities, other than the big hassle of
> jackhammering, digging, and pouring more concrete and rebar into an
> otherwise good foundation. I want the dormers and the patio deck. Can
> I spread the load from these trusses to adjacent trusses for example?
> Ideas wanted before I deal with the truss company again.
There are many ways to do it. You could make the first floor wall a
box beam, you could install a header above the top plate and have the
trusses hung off of that, you could let in a header into the first
floor framing, etc.
R
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Posted by Alan on August 5, 2006, 2:17 am
I don't exactly follow the ideas given. My garage door headers are
already in contact with the top plate, so if I simply put another
header on top of this, I don't see how I'm getting rid of the point
load. The local architect at the planning department says I would need
a 3-1/3 cube footer of concrete and rebar to support the 10,000lbs of
point load, and since I have two such trusses, that means four of these
huge concrete blocks, in and through an existing foundation as
described. Calculating the divided loads of a header will mean hiring
an engineer in addition to the truss company. My current thinking, to
avoid so much professional consultation, jackhammer and concrete hassle
is to have the truss company redesign the trusses to distribute load
from just the two opposing walls that are 34' apart, into three point
loads, one of which is one an engineered truss beam running down the
middle of the garage, perpendicular to the trusses, parallel to the
stressed two walls/foundations. This would put some of the point loads
on the other two walls which so far are hardly being tested by the
truss system. But, I can't figure out how many of these engineered
members I because I don't know what the max my current foundation can
take in terms of point load lbs. If you can clarify the ideas you have
in mind, I'd appreciate this....
RicodJour wrote:
> Alan wrote:
> > I provided a truss company the basics of my present garage, so that
> > they could design a new roof for it. I told them I have 18"D by 15"W
> > perimeter foundation, which is suitable for support of two story house
> > in my county. I also told them that I have 16" OC 2x4 stud walls with
> > double top plate, also capable of supporting a second story by code.
> > Some of this information was provided in drawings and other by e-mail.
> > The computer techie designer spent a lot of time with me on a truss
> > system, I put half down and got engineered stamped calculations. When
> > I managed to have a presubmisson review by the senior architect at the
> > planning department, he told me that the point load for two multiply
> > trusses, which support the ladder of joists supporting dormers and a
> > deck, exceed the point load capability of the foundation. Can anybody
> > tell me how to calculate what point load my foundation can take? Also,
> > need help considering possibilities, other than the big hassle of
> > jackhammering, digging, and pouring more concrete and rebar into an
> > otherwise good foundation. I want the dormers and the patio deck. Can
> > I spread the load from these trusses to adjacent trusses for example?
> > Ideas wanted before I deal with the truss company again.
>
> There are many ways to do it. You could make the first floor wall a
> box beam, you could install a header above the top plate and have the
> trusses hung off of that, you could let in a header into the first
> floor framing, etc.
>
> R
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Posted by Alan on August 5, 2006, 2:31 am
Maybe I wrote too soon. Are you suggesting that if I rip off the top
plate, and down the studs, say 12" or so, and install a header into the
void to make-up back to the height of the original top plate, I would
effectively be able to convert the point loads into weight distributed
along all the studs and the axis of the entire wall foundation, or a
least also whatever is the length of the header? Just to clarify,
these trusses cantilever over the top plate to create a soffett eave,
rather than simply have rafter ends exposed, and they are also designed
to raised the height of the eave because they have a heal height of 12"
at the bearing wall. Of the 7 trusses, 5 are OK in terms of point
load, but each of the two center multi-ply trusses that support the
dormers and 8' of floorspace between them produce about 10,000 lbs load
on each end. 10,000lbs is apparently too much point load...
>
> There are many ways to do it. You could make the first floor wall a
> box beam, you could install a header above the top plate and have the
> trusses hung off of that, you could let in a header into the first
> floor framing, etc.
>
> R
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Posted by Wayne Whitney on August 5, 2006, 11:18 am
> Are you suggesting that if I rip off the top plate, and down the
> studs, say 12" or so, and install a header into the void to make-up
> back to the height of the original top plate, I would effectively be
> able to convert the point loads into weight distributed along all
> the studs and the axis of the entire wall foundation, or a least
> also whatever is the length of the header?
A header will distribute the loads from above (usually a distributed
load, but in your case a point load) into two point loads, one at each
end of the header. So the advantage in your case is to take a single
point load and transform it into two offset point loads half the size.
Cheers, Wayne
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