question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?


They would be ok, but I would go with the TGI beams.

I think you have a reason to be concerned. Search the internet using
google. I think you will find many stories of gusset plate failures when
used in floors. Ok for roofs but I would never have a floor built that way.
One story I read a while back was a condo that they had to rip out ceilings
and sister every truss with a solid beam. It is going back a few years but
if I remember correctly the original manufacturer who had invented the
system had misrepresented strength and engineers had been relying on those
numbers when designing floors.


wrote in message
oups.com...
question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

On May 17, 8:25 pm, "Art" wrote:
I think you have a reason to be concerned. Search the internet using
google. I think you will find many stories of gusset plate failures when
used in floors. Ok for roofs but I would never have a floor built that way.
One story I read a while back was a condo that they had to rip out ceilings
and sister every truss with a solid beam. It is going back a few years but
if I remember correctly the original manufacturer who had invented the
system had misrepresented strength and engineers had been relying on those
numbers when designing floors.

wrote in message

oups.com...

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

is the 2x8 part of an attic truss? if so, then they would be
engineered and will be fine. I joists might support more load, but I
assume the project has some budget---I joists would require second
floor framing or perhaps a hand framed roof, all more expensive.

Hopefully, because it is a truss, there are some support members such as
vertical framing to form walls that would add strength to 24 feet of 2 x 8s
with a joint in the middle. Otherwise I would be concerned with its
usability for storage.

"marson" wrote in message
oups.com...
On May 17, 8:25 pm, "Art" wrote:
I think you have a reason to be concerned. Search the internet using
google. I think you will find many stories of gusset plate failures when
used in floors. Ok for roofs but I would never have a floor built that
way.
One story I read a while back was a condo that they had to rip out
ceilings
and sister every truss with a solid beam. It is going back a few years
but
if I remember correctly the original manufacturer who had invented the
system had misrepresented strength and engineers had been relying on
those
numbers when designing floors.

wrote in message

oups.com...

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

is the 2x8 part of an attic truss? if so, then they would be
engineered and will be fine. I joists might support more load, but I
assume the project has some budget---I joists would require second
floor framing or perhaps a hand framed roof, all more expensive.

wrote:
question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions

A couple of things don't seem quite right he there are commercial
trusses stacked up in the yards at all the box stores and lumber yards
and I have (so far) never seen any up to 30' or so with a bottom chord
bigger than a 2 x 4. Seems to me that a 2 x 8 is a huge overkill.
You're not going to be storing a dozen or so Chevy 350 crate engines
up there, are you?
Truss chord mambers are often (maybe usually) mated with 'nailing
plates' at junctions with other truss bracing elements.
If your contractor is building his own trusses, better back off and
order the proper engineered and factory built types. If he doesn't
have a properly architect-designed system it may not pass your local
building inspector. HTH

Joe

In article .com,
) says...
question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

As long as there is a bearing wall or heavy beam under the joists where
they meet in the middle, it will be fine. Otherwise, forget it.

Let me guess: either you live in some backwoods community with no
building codes, or you are trying to bootleg a building in without a
permit. What you are describing would never pass a structural plan
check or inspection.

Do a quick structural calc. Suppose you want to load just the center
12' of the upstairs with something fairly heavy, say 100 psf. If the
joists are 16" on center, that means each joist has to support 1560 lbs,
plus the weight of the lumber and decking. Divide by 2 (two joists)
times 12' of lever arm, divided by 2/3 of a foot (8 inch joist) gives
14,040 lbs. of tension on the bottom edge of that gusset plate. Now how
do you think it's going to work?

--
For email, replace firstnamelastinitial
with my first name and last initial.

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

Joists or trusses? Your confusion alone is worrisome.

You want engineered floor trusses for that span and load. Not joists
assembled by the contractor.

Joe wrote:

A couple of things don't seem quite right he there are commercial
trusses stacked up in the yards at all the box stores and lumber yards
and I have (so far) never seen any up to 30' or so with a bottom chord
bigger than a 2 x 4. Seems to me that a 2 x 8 is a huge overkill.

Standard roof trusses are designed to carry weight on the *roof*, not on
the bottom truss members.

Unless specifically engineered for it, the bottom truss members will
only be designed to handle the weight of the ceiling and insulation,
with enough extra to let people walk around up in the attic safely.

Chris

wrote in message
oups.com...
| question on trusses. contractor is building a stand-alone garage
| 24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
| joists, mated in the middle with a gusset plate.
|
| is this sufficient for bearing weight on the 2nd floor for storage?
| some reason I thought wood-composite i-beams were better. he said the
| gusset-type should be fine.
|
| yes? no? opinions?
|

rip it out and do it the right way.
floors can NOT have splices or nailers in them.
24 ft span...........2x8......................under sized for storage.
TJI's would work best......................1 piece.............no
joints.

or add a strong back to the top of the spliced joists.

On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.

On May 18, 6:22 am, under construction wrote:
On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.


There are a lot of people posting on this thread that have never seen
a set of attic trusses. If your contractor is using attic roof
trusses, they commonly come with spliced 2x8's for bottom chords.
These will be engineered and gauranteed for a certain load. They do
come with some caveats--usually the specs call for no holes and of
course no alterations. I have installed many sets of these. Again,
they do have splice plates. I have used them in houses as well as
garage storage areas. Trusses usually come with a packet that will
spell out the assumed loads--your contractor should have that. It
does not mean that your contractor is not good. Floor joist can have
splices. You do not have to rip it out and do it the right way. What
you are doing would indeed pass inspection.

On May 18, 6:55 am, marson wrote:
On May 18, 6:22 am, under construction wrote:



On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.

There are a lot of people posting on this thread that have never seen
a set of attic trusses. If your contractor is using attic roof
trusses, they commonly come with spliced 2x8's for bottom chords.
These will be engineered and gauranteed for a certain load. They do
come with some caveats--usually the specs call for no holes and of
course no alterations. I have installed many sets of these. Again,
they do have splice plates. I have used them in houses as well as
garage storage areas. Trusses usually come with a packet that will
spell out the assumed loads--your contractor should have that. It
does not mean that your contractor is not good. Floor joist can have
splices. You do not have to rip it out and do it the right way. What
you are doing would indeed pass inspection.

Here is a drawing of an attic truss. Note the splice plate in the
bottom chord. http://service.govdelivery.com/docs/...0051014_en.pdf

On 18 May 2007 04:55:26 -0700, marson wrote:

On May 18, 6:22 am, under construction wrote:
On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.


There are a lot of people posting on this thread that have never seen
a set of attic trusses. If your contractor is using attic roof
trusses, they commonly come with spliced 2x8's for bottom chords.
These will be engineered and gauranteed for a certain load. They do
come with some caveats--usually the specs call for no holes and of
course no alterations. I have installed many sets of these. Again,
they do have splice plates. I have used them in houses as well as
garage storage areas. Trusses usually come with a packet that will
spell out the assumed loads--your contractor should have that. It
does not mean that your contractor is not good. Floor joist can have
splices. You do not have to rip it out and do it the right way. What
you are doing would indeed pass inspection.


First of all, your diagram (other post) is NOT a "floor joist" but
rather a chord member for a truss. That said, floor joists should
not have splices especially in the middle (in commercial structures
they use drop in beams). The reason your chord member (in your
diagram) has a splice in the middle is that it is a tension member.
If you are going to help at least give correct advice.

On May 18, 9:24 am, under construction wrote:
On 18 May 2007 04:55:26 -0700, marson wrote:



On May 18, 6:22 am, under construction wrote:
On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.

There are a lot of people posting on this thread that have never seen
a set of attic trusses. If your contractor is using attic roof
trusses, they commonly come with spliced 2x8's for bottom chords.
These will be engineered and gauranteed for a certain load. They do
come with some caveats--usually the specs call for no holes and of
course no alterations. I have installed many sets of these. Again,
they do have splice plates. I have used them in houses as well as
garage storage areas. Trusses usually come with a packet that will
spell out the assumed loads--your contractor should have that. It
does not mean that your contractor is not good. Floor joist can have
splices. You do not have to rip it out and do it the right way. What
you are doing would indeed pass inspection.

First of all, your diagram (other post) is NOT a "floor joist" but
rather a chord member for a truss. That said, floor joists should
not have splices especially in the middle (in commercial structures
they use drop in beams). The reason your chord member (in your
diagram) has a splice in the middle is that it is a tension member.
If you are going to help at least give correct advice.

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248. Why would you use
an attic truss if you couldn't use the space created for a room?

The OP used the term "floor joist", but I suspect that he is looking
at the bottom chord of an attic truss. He needs to clarify this.
Since most attic trusses will have a spliced bottom chord, I suspect
that is what he has, and his contractor hasn't given him a very good
answer.

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.
is this sufficient for bearing weight on the 2nd floor for storage?

If the 2x8 is the bottom chord of an engineered "attic truss", it's
probably sized for the intended loads. The other chords of the truss help
carry the load, the same way a 2x4 is typically used to build a standard
truss. The 2x8 would essentially be sized to carry the load between the
truss chords (maybe 10 feet for a typical attic truss?). Assuming the truss
is being built by a truss company, they should be able to supply you (or
your contractor) with a copy of the engineering diagrams and the loads it
is designed to carry. In fact, that's one of the required items for
building permits around here, so it may already be part of the plan
package.

On the other hand, if you're talking individual 2x8's for spanning 24'
you're going to have big problems. Even when sized for a ceiling joist, a
2x8 at 16" OC is only good for about 17 feet, and that's for a very light
load. You'll never get by spanning 24 feet with a 2x8.

Just for reference, I spanned 24' in my garage using 2x12's at 16" OC. Even
that is way undersized for a floor joist. It works OK for my light attic
storage (empty boxes, Christmas decorations, suitcases, etc.), but it is
far too bouncy to be considered a usable floor joist.

14" I-joists would probably work well if you have the vertical space to
install them.

"IF" you have a beam running down the middle of the garage, your span would
only be 12', in which case 2x8 joists would probably be perfect for floor
joists. You could even splice shorter joists over the beam if needed.

However, if you DO NOT have a beam, any splice in the joist is going to be
an immediate failure point (unless it's part of an engineered truss).

Anthony

On 18 May 2007 07:48:26 -0700, marson wrote:

On May 18, 9:24 am, under construction wrote:
On 18 May 2007 04:55:26 -0700, marson wrote:



On May 18, 6:22 am, under construction wrote:
On 17 May 2007 18:18:17 -0700, wrote:

question on trusses. contractor is building a stand-alone garage
24'x30'. 2nd floor is for storage. he's using 2x8 lumber for the floor
joists, mated in the middle with a gusset plate.

is this sufficient for bearing weight on the 2nd floor for storage?
some reason I thought wood-composite i-beams were better. he said the
gusset-type should be fine.

yes? no? opinions?

I'm a bit confused. You say question about trusses but I don't think
you are describing trusses? To me, you are describing a 24' long 2x8
spliced in the center of the span, right? Also, are you building a 2
story garage so there is a floor at the 2nd story or is it just a
normal garage where the ceiling chords are going to be used for
storage above?

Assuming a 2 story garage with a long 2x8 with a splice in the middle
of the span and NO support in the middle (like a column or beam) you
do NOT want this. Not only will it not support a FLOOR load but it
will also DEFLECT too much. And if these members are only ceiling
chords as in a normal garage, I'd still want no splices and at least
2x10 members.

Please do yourself a favor and hire an engineer or architect for
adequate member sizes. It sounds to me like the contractor is not
good or is trying to keep the cost very low by building a subquality
garage. Over the years you will be sorry about this garage.

There are a lot of people posting on this thread that have never seen
a set of attic trusses. If your contractor is using attic roof
trusses, they commonly come with spliced 2x8's for bottom chords.
These will be engineered and gauranteed for a certain load. They do
come with some caveats--usually the specs call for no holes and of
course no alterations. I have installed many sets of these. Again,
they do have splice plates. I have used them in houses as well as
garage storage areas. Trusses usually come with a packet that will
spell out the assumed loads--your contractor should have that. It
does not mean that your contractor is not good. Floor joist can have
splices. You do not have to rip it out and do it the right way. What
you are doing would indeed pass inspection.

First of all, your diagram (other post) is NOT a "floor joist" but
rather a chord member for a truss. That said, floor joists should
not have splices especially in the middle (in commercial structures
they use drop in beams). The reason your chord member (in your
diagram) has a splice in the middle is that it is a tension member.
If you are going to help at least give correct advice.

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248. Why would you use
an attic truss if you couldn't use the space created for a room?

The OP used the term "floor joist", but I suspect that he is looking
at the bottom chord of an attic truss. He needs to clarify this.
Since most attic trusses will have a spliced bottom chord, I suspect
that is what he has, and his contractor hasn't given him a very good
answer.


Just to clarify, I agree that bottom chords can have bending between
panel points if engineered accordingly but generally they are tension
members. Notice tho even as in floor joists, the splice is not in
the middle to avoid maximum stresses.

I agree w/ your 2nd paragraph.

under construction wrote:

Notice tho even as in floor joists, the splice is not in
the middle to avoid maximum stresses.

Actually, take a look at truss A288 at the same site. The splice is
dead-center.

Chris

marson wrote:

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248.

Note that the 40psf is a live load and so is expected to be temporary.
The specified dead load for the bottom chord in the room area is only 5psf.

Chris

On May 18, 11:28 am, Chris Friesen wrote:
marson wrote:
Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248.

Note that the 40psf is a live load and so is expected to be temporary.
The specified dead load for the bottom chord in the room area is only 5psf.

Chris

And why would that be any different than any other joist or rafter?

On Fri, 18 May 2007 10:21:54 -0600, Chris Friesen
wrote:

under construction wrote:

Notice tho even as in floor joists, the splice is not in
the middle to avoid maximum stresses.

Actually, take a look at truss A288 at the same site. The splice is
dead-center.

Chris


I'll take your word on that but generally it's not good practice to do
that but that doesn't mean it can't be done. It generally means heavy
plates and more nails to carry the additional stresses.

On Fri, 18 May 2007 10:28:56 -0600, Chris Friesen
wrote:

marson wrote:

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248.

Note that the 40psf is a live load and so is expected to be temporary.
The specified dead load for the bottom chord in the room area is only 5psf.

Chris

Agreed temporary in so far as it can be removed but it doesn't have to
be. Regardless, it still has to be designed for as a bending stress
in the chord member.

On Fri, 18 May 2007 11:54:13 -0500, under construction wrote:

On Fri, 18 May 2007 10:21:54 -0600, Chris Friesen
wrote:

under construction wrote:

Notice tho even as in floor joists, the splice is not in
the middle to avoid maximum stresses.

Actually, take a look at truss A288 at the same site. The splice is
dead-center.

Chris


I'll take your word on that but generally it's not good practice to do
that but that doesn't mean it can't be done. It generally means heavy
plates and more nails to carry the additional stresses.

I meant to say not heavy plates but "thicker" plates. My bad.

Cindy Boucher wrote:

24 ft span... 2x8...

With a perfect splice, S = bd^2/6 = 1.5x7.25^2/6 = 13.1 in^3 and
M = fS = 13100 in-lb and W = 8M/L = 8x13100/(12x24) = 365 pounds
of total load, ie 15.2 pounds per linear foot or 11.4 psf on 16"
centers, if I did that right.

So maybe we need more than a perfect splice, eg a kingpost
or a truss or a wall under the middle.

Nick

Yep, "bottom chord of an attic truss" is what I am referring to. Your
link is precisely what the contractor is using. After reading these
posts, I obtained the diagrams from the truss company, and it appears
they can bear 60 psf (40 live load, the rest I'm assuming dead load).

Thanks.

The OP used the term "floor joist", but I suspect that he is looking
at the bottom chord of an attic truss. He needs to clarify this.
Since most attic trusses will have a spliced bottom chord, I suspect
that is what he has, and his contractor hasn't given him a very good
answer.

Yep - bottom chord of an engineered attic truss from a truss company.
After reading your post, got the truss company to send over the
engineering diagrams - turns out it can support 60 psf (40 ll +
remaining dead load I'm assuming). Wasn't required for our permit,
but I'm sure the building inspector will be happy to see it in
writing.

Thanks.

If the 2x8 is the bottom chord of an engineered "attic truss", it's
probably sized for the intended loads. The other chords of the truss help
carry the load, the same way a 2x4 is typically used to build a standard
truss. The 2x8 would essentially be sized to carry the load between the
truss chords (maybe 10 feet for a typical attic truss?). Assuming the truss
is being built by a truss company, they should be able to supply you (or
your contractor) with a copy of the engineering diagrams and the loads it
is designed to carry. In fact, that's one of the required items for
building permits around here, so it may already be part of the plan
package.

In article .com,
(marson) says...

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248. Why would you use
an attic truss if you couldn't use the space created for a room?

You need to learn to read a spec sheet. The bottom chord is designed
for a 10 psf live load (note 9).

--
For email, replace firstnamelastinitial
with my first name and last initial.

On May 19, 10:13 am, Larry Caldwell
wrote:
In article .com,
(marson) says...

Here is a link for the engineering of an attic truss. Note the splice
in the bottom chord. Note the bottom chord loading of 40 psf.
http://www.wsitruss.com/Prod_Frame.asp?Truss=A248. Why would you use
an attic truss if you couldn't use the space created for a room?

You need to learn to read a spec sheet. The bottom chord is designed
for a 10 psf live load (note 9).

--
For email, replace firstnamelastinitial
with my first name and last initial.

That's for the bottom chord as a whole. For the room area (10-12) live
load is 40 psf. Wouldn't meet code in most places if it wasn't.
Again, attic trusses have been in use for many years. I gotta wonder
how much experience you have if you've never seen them.