House was built in '74 using trusses made of 2x4s. It needs a neew roof and
the design of the house lends itself to replacing the asphalt shingles with
Spanish terra cotta tiles. In this case probably the light weight concrete
ones. Roofer said the existing trusses will never support the extra load and
I agree.His suggestion was to build new trusses sistered next to the old one
out of enginner lumber(wood I beams) not that difficult to do in this attic
but probably very labor intensive. I need something me and some of my poker
buddies can do without hiring a crew.
I have at least couple of years to do this project before thes roof has to
be replaced, I figure since wood I-beams are so strong. box beams would be
even stronger. My plan is to use use 9" strips of OSB one each side of the
joist and rafters and completing the box beam with another 2x4. This is
something I could do myself over the course of a couple of years or less.
Attic is tall and has a 6 ft wide walkway down the center. Insulation is
sheets of rigid foam.

Also could build I beams in place using exsiting trusses as part of the I.

Any thoughts on my plan would be appreciated.

On 10-Apr-2006, " wrote:

I figure since wood I-beams are so strong. box beams would be
even stronger. My plan is to use use 9" strips of OSB one each side of the
joist and rafters and completing the box beam with another 2x4

If the stuff you build ends up stiffer than the existing trusses, they will take most
fo the load. If it is less stiff, it will not take load until the existing trusses have
deflected somewhat. If your upgrade isn't matched to the existing trusses, you may
end up not improving the situation at all.

When the roofer told you to sister the existing trusses, he should have said to make
them the same as the existing ones or sister with components that will move with
the existing ones _exactly_.

Before you go on with this, get the advice of an expert.

Mike

PS a box beam is only as strong as the shear strength of the join between the
webs and the flanges. Do you know what it takes to make that right?

My reaction too.
Have an engineer analyse the existing trusses.
or
Ask a truss builder to price new trusses for the new load.
In addition, the clips and ties holding the trusses to the building
probably don't meet code.
An engineer can tell you that too.
TB

yeah, call a truss company. they have engineers who are used to roof
trusses.

Of course, this is an opportune time to consider pulling the whole
roof, trusses included, and putting in a cathedral ceiling, or another
room, etc.

Dave

I doubt your plan to make your own box beams would give you anything
near the strength of a manufactured "wood I-beam". The companies that
make the I-beams hire engineers and specialists in materials to design
these things, and for that you end up something that is known to work.
Your poker buddies are likely to just slap together scraps of whatever
OSB and nails and glue they have lying around, hoping to get something
that sort of looks like the real thing, at least in appearance.

"kevin" wrote in message
oups.com...
I doubt your plan to make your own box beams would give you anything
near the strength of a manufactured "wood I-beam". The companies that
make the I-beams hire engineers and specialists in materials to design
these things, and for that you end up something that is known to work.
Your poker buddies are likely to just slap together scraps of whatever
OSB and nails and glue they have lying around, hoping to get something
that sort of looks like the real thing, at least in appearance.


Actually we have made I beams with OSB and 2X4s for a boat house. Local
supplier didnt have them and we didnt meet the minimum order. My poker
buddies are a pretty savy group with a couple of EEs in the group. There is
a stuctural engineer in the group but he say he hasnt done anything with
wood in 30 years and any real engineering at all in 15 years. I havent been
able to get them around to the house yet but in a couple of weeks we will be
down at the house and I can get them together for poker and steaks. Then I
can see what they know.

Some of the comments did get me thinking. Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is and
how much a given lenght deflects under load. I figure this will give whoever
takes a look at it a good starting point. Any other way of doing except by
my plan would probably be too expensive to meet my budget. Would be nice if
I found out I didn't have to do anything at all to it.

wrote:
"kevin" wrote in message
oups.com...
I doubt your plan to make your own box beams would give you anything
near the strength of a manufactured "wood I-beam". The companies that
make the I-beams hire engineers and specialists in materials to design
these things, and for that you end up something that is known to work.
Your poker buddies are likely to just slap together scraps of whatever
OSB and nails and glue they have lying around, hoping to get something
that sort of looks like the real thing, at least in appearance.


Actually we have made I beams with OSB and 2X4s for a boat house. Local
supplier didnt have them and we didnt meet the minimum order. My poker
buddies are a pretty savy group with a couple of EEs in the group. There is
a stuctural engineer in the group but he say he hasnt done anything with
wood in 30 years and any real engineering at all in 15 years. I havent been
able to get them around to the house yet but in a couple of weeks we will be
down at the house and I can get them together for poker and steaks. Then I
can see what they know.

Some of the comments did get me thinking. Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is and
how much a given lenght deflects under load. I figure this will give whoever
takes a look at it a good starting point. Any other way of doing except by
my plan would probably be too expensive to meet my budget. Would be nice if
I found out I didn't have to do anything at all to it.

Stop guessing & get an engineer to take a look at the roof system,

There is no need to build a test specimen, that's what calcs are for

Shop around for an engineer who would be willling to design a fix (if
any fix is needed) that could be built onsite by your group.

cheers
Bob

On 11-Apr-2006, " wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real engineered beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like asking my mother
to put aside her knitting needles and design a new space shuttle. If you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is and
how much a given lenght deflects under load. I figure this will give whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing roof can do so
what will knowing about box beams tell you? It is entirely possible that the existing
trusses have sufficient reserve capacity to support the planned roof upgrade. If
they cannot, the box beam doesn't sound like the right solution anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find out what it will
cost. Then decide on whether you should do this at all. You and your buddies
don't sound like a good solution.

Mike

"Michael Daly" wrote in message
...

On 11-Apr-2006, "
wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real engineered
beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like asking
my mother
to put aside her knitting needles and design a new space shuttle. If
you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is
and
how much a given lenght deflects under load. I figure this will give
whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing roof can
do so
what will knowing about box beams tell you? It is entirely possible that
the existing
trusses have sufficient reserve capacity to support the planned roof
upgrade. If
they cannot, the box beam doesn't sound like the right solution anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find out
what it will
cost. Then decide on whether you should do this at all. You and your
buddies
don't sound like a good solution.

Mike

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this point
in your life should come when you are about 12.LOL

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local college
ths morning. Just wishful thinking I guess.

Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

wrote:
"Michael Daly" wrote in message
...

On 11-Apr-2006, "
wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real engineered
beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like asking
my mother
" to put aside her knitting needles and design a new space shuttle.
If
you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is
and
how much a given lenght deflects under load. I figure this will give
whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing roof can
do so
what will knowing about box beams tell you? It is entirely possible that
the existing
trusses have sufficient reserve capacity to support the planned roof
upgrade. If
they cannot, the box beam doesn't sound like the right solution anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find out
what it will
cost. Then decide on whether you should do this at all. You and your
buddies
don't sound like a good solution.

Mike

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this point
in your life should come when you are about 12.LOL

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local college
ths morning. Just wishful thinking I guess.

Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

SNIP

"found my box beam plan was way overkill"

SNIP

"I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. "

Really?

cheers
Bob

On 12-Apr-2006, " wrote:

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this point
in your life should come when you are about 12.LOL

You and your friends are obviously in your manic phase. I hope you come to your
senses before you collapse your house on someone. You _think_ you know
what you're doing or can figure it out yourselvest - I've got more than enough years
as a structural engineer to know you don't.

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local college
ths morning. Just wishful thinking I guess.

You got advice but you haven't taken it. The advice that was repeated by several
posters was "get a professional to check it out." Just because that's not what
you want to hear, doesn't mean you didn't get good advice.

Mike

EE = Electrical Engineering, right?

If you had appendicitis, would you hand a medical book and a scapel to one of
your EE buddies?


Actually, you've got to be careful even asking people to
perform within their nominal field, if you're in
a sub-genre they're not used to.

I took a drawing of my attic to a game session with
some of my friends that included PEs in three different
specialties, because I wanted them to check my math,
and it still took me about 90 minutes to convince
them that the bottom chord of a truncated queen-post
truss is a tension member.

In article , Goedjn says...




EE = Electrical Engineering, right?

If you had appendicitis, would you hand a medical book and a scapel to one of
your EE buddies?


Actually, you've got to be careful even asking people to
perform within their nominal field, if you're in
a sub-genre they're not used to.

I took a drawing of my attic to a game session with
some of my friends that included PEs in three different
specialties, because I wanted them to check my math,
and it still took me about 90 minutes to convince
them that the bottom chord of a truncated queen-post
truss is a tension member.

OK - I'll take your word for it

Banty (metallurgist by training)


--
NewsGuy.Com 30Gb $9.95 Carry Forward and On Demand Bandwidth

I did find out that just adding 3-1/2" OSB strips will more than triple the strenght
of the existing 2x4 trusses.

Are you talking about a full-length continuous piece of OSB? Where do
you find 3-1/2" x 20' strips of OSB? I know the engineered wood
companies use single pieces for building their beams. But all I have is
8' lengths.

"BobK207" wrote in message
ups.com...

wrote:
"Michael Daly" wrote in message
...

On 11-Apr-2006, "
wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real engineered
beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like
asking
my mother
" to put aside her knitting needles and design a new space shuttle.
If
you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength is
and
how much a given lenght deflects under load. I figure this will give
whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing roof
can
do so
what will knowing about box beams tell you? It is entirely possible
that
the existing
trusses have sufficient reserve capacity to support the planned roof
upgrade. If
they cannot, the box beam doesn't sound like the right solution anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find
out
what it will
cost. Then decide on whether you should do this at all. You and your
buddies
don't sound like a good solution.

Mike

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if
they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this
point
in your life should come when you are about 12.LOL

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local
college
ths morning. Just wishful thinking I guess.

Went to test my box beam(built it this AM) at local junior college and
found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find
out
the load of the shingles compared to the concrete tiles.

SNIP

"found my box beam plan was way overkill"

SNIP

"I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. "

Really?

cheers
Bob

Yes, I should have been more clear, That is a piece of 1/2" OSB on each side
of the truss. I was thinking plywood would be even better but found the OSB
is stronger. Plywood would be more than sufficent for my purposes and has
the advantage of being easily glued to the existing truss, the OSB I am
familar with has a waxy coating on it. Is it all like this? We discussed the
possibility of actually building trusses like I suggested. In the real world
it would be easier and cheaper to build them of enginnered lumber but
thought my idea would be plausibe for stengthening an existing structure. He
also thought there was a very good chance that the existing trusses would
work "as is" considering the truss was designed to span the full width of
the house and there are a lot of internal walls that could be load bearing.
For hte most part ther is a load bearing wall that runs almost all of the
way through the center of the house . The exceptions are the den area where
the load walls would be about 1/3 the way in on each side and for about 4 ft
where the dining room on the back side of the house overlaps the livingroom
on the front ther is a 4 foot wide area where the trusses are only supported
by the outside walls. Several years ago there was a problem with the ceiling
cracking in this area. The problem was fixed by placing 2 beams across 6
ceiling joist to support the 2 ceiling joist that otherwise were unsupported
except on the ends.

" wrote in message
...

"BobK207" wrote in message
ups.com...

wrote:
"Michael Daly" wrote in message
...

On 11-Apr-2006, "
wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real engineered
beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like
asking
my mother
" to put aside her knitting needles and design a new space shuttle.
If
you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength
is
and
how much a given lenght deflects under load. I figure this will give
whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing roof
can
do so
what will knowing about box beams tell you? It is entirely possible
that
the existing
trusses have sufficient reserve capacity to support the planned roof
upgrade. If
they cannot, the box beam doesn't sound like the right solution
anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find
out
what it will
cost. Then decide on whether you should do this at all. You and your
buddies
don't sound like a good solution.

Mike

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is
the
one thing we have in common. Im sure my EE friends will let me know if
they
cant handle it. They are at the point in their lives where they can
learn
something new for themselves without taking a class. My dad said this
point
in your life should come when you are about 12.LOL

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local
college
ths morning. Just wishful thinking I guess.

Went to test my box beam(built it this AM) at local junior college and
found
my box beam plan was way overkill. While I didnt get to test it(forgot
it
was Spring break), I did find out that just adding 3-1/2" OSB strips
will
more than triple the strenght of the existing 2x4 trusses. Now to find
out
the load of the shingles compared to the concrete tiles.

SNIP

"found my box beam plan was way overkill"

SNIP

"I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. "

Really?

cheers
Bob

Yes, I should have been more clear, That is a piece of 1/2" OSB on each
side of the truss. I was thinking plywood would be even better but found
the OSB is stronger. Plywood would be more than sufficent for my purposes
and has the advantage of being easily glued to the existing truss, the OSB
I am familar with has a waxy coating on it. Is it all like this? We
discussed the possibility of actually building trusses like I suggested.
In the real world it would be easier and cheaper to build them of
enginnered lumber but thought my idea would be plausibe for stengthening
an existing structure. He also thought there was a very good chance that
the existing trusses would work "as is" considering the truss was designed
to span the full width of the house and there are a lot of internal walls
that could be load bearing. For hte most part ther is a load bearing wall
that runs almost all of the way through the center of the house . The
exceptions are the den area where the load walls would be about 1/3 the
way in on each side and for about 4 ft where the dining room on the back
side of the house overlaps the livingroom on the front ther is a 4 foot
wide area where the trusses are only supported by the outside walls.
Several years ago there was a problem with the ceiling cracking in this
area. The problem was fixed by placing 2 beams across 6 ceiling joist to
support the 2 ceiling joist that otherwise were unsupported except on the
ends.


Went down to the house this past week and got the guys to show up with an
offer of steaks beer and poker, this is where I found that this kind of
engineering isnt as mystical as I thought. There are programs available just
for this sort of thing. We spent about 30 minutes in the attic taking some
measurements and then plugged them into the computer. What we found was that
the existing manufactured trusses were just fine to use with the concrete
roofing tiles the hip ends of the roof are another story being stick built
on site. These need some improvements but not a whole lot, just two pieces
of 2x4 per truss. The big problem is that almost every damn one of them has
to be a different length.

" wrote in message
...

" wrote in message
...

"BobK207" wrote in message
ups.com...

wrote:
"Michael Daly" wrote in message
...

On 11-Apr-2006, "

wrote:

Actually we have made I beams with OSB and 2X4s for a boat house.

And how do you know it is anywhere near the spec for a real
engineered
beam?

a pretty savy group with a couple of EEs in the group

Asking an electrical engineer to solve a structural problem is like
asking
my mother
" to put aside her knitting needles and design a new space shuttle.
If
you want a
structural problem solved, you get a structural engineer.

Plan on building a test section of
the box beam mades of OSB and 2x4 and see what the failure strength
is
and
how much a given lenght deflects under load. I figure this will give
whoever
takes a look at it a good starting point.

A good starting point for what? You don't know what the existing
roof can
do so
what will knowing about box beams tell you? It is entirely possible
that
the existing
trusses have sufficient reserve capacity to support the planned roof
upgrade. If
they cannot, the box beam doesn't sound like the right solution
anyway.

Any other way of doing except by
my plan would probably be too expensive to meet my budget.

Then sell the house. Either do it right or walk away.

Better: Start with an expert and find out what you _need_, then find
out
what it will
cost. Then decide on whether you should do this at all. You and
your
buddies
don't sound like a good solution.

Mike

Obviously you dont know the capabilites of my friends or me. If we
dont
know we learn. We really hate spending money for not knowing. That is
the
one thing we have in common. Im sure my EE friends will let me know if
they
cant handle it. They are at the point in their lives where they can
learn
something new for themselves without taking a class. My dad said this
point
in your life should come when you are about 12.LOL

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local
college
ths morning. Just wishful thinking I guess.

Went to test my box beam(built it this AM) at local junior college and
found
my box beam plan was way overkill. While I didnt get to test it(forgot
it
was Spring break), I did find out that just adding 3-1/2" OSB strips
will
more than triple the strenght of the existing 2x4 trusses. Now to find
out
the load of the shingles compared to the concrete tiles.

SNIP

"found my box beam plan was way overkill"

SNIP

"I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. "

Really?

cheers
Bob

Yes, I should have been more clear, That is a piece of 1/2" OSB on each
side of the truss. I was thinking plywood would be even better but found
the OSB is stronger. Plywood would be more than sufficent for my purposes
and has the advantage of being easily glued to the existing truss, the
OSB I am familar with has a waxy coating on it. Is it all like this? We
discussed the possibility of actually building trusses like I suggested.
In the real world it would be easier and cheaper to build them of
enginnered lumber but thought my idea would be plausibe for stengthening
an existing structure. He also thought there was a very good chance that
the existing trusses would work "as is" considering the truss was
designed to span the full width of the house and there are a lot of
internal walls that could be load bearing. For hte most part ther is a
load bearing wall that runs almost all of the way through the center of
the house . The exceptions are the den area where the load walls would be
about 1/3 the way in on each side and for about 4 ft where the dining
room on the back side of the house overlaps the livingroom on the front
ther is a 4 foot wide area where the trusses are only supported by the
outside walls. Several years ago there was a problem with the ceiling
cracking in this area. The problem was fixed by placing 2 beams across 6
ceiling joist to support the 2 ceiling joist that otherwise were
unsupported except on the ends.


Went down to the house this past week and got the guys to show up with an
offer of steaks beer and poker, this is where I found that this kind of
engineering isnt as mystical as I thought. There are programs available
just for this sort of thing. We spent about 30 minutes in the attic taking
some measurements and then plugged them into the computer. What we found
was that the existing manufactured trusses were just fine to use with the
concrete roofing tiles the hip ends of the roof are another story being
stick built on site. These need some improvements but not a whole lot,
just two pieces of 2x4 per truss. The big problem is that almost every
damn one of them has to be a different length.


I had a chance this past weekend to check out a house with the Spanish tile
roof like I want. The house was only a few miles awy from the house I want o
put them on. When I went up into the attic I was amazed at how much cooler
the house with the spanish tiles was.Up until my visit the way the my house
would look was only in my imagination. The outside this house is nearly
identical to mine and the ties make it gorgeous.

kevin wrote:
I doubt your plan to make your own box beams would give you anything
near the strength of a manufactured "wood I-beam". The companies that
make the I-beams hire engineers and specialists in materials to design
these things, and for that you end up something that is known to work.
Your poker buddies are likely to just slap together scraps of whatever
OSB and nails and glue they have lying around, hoping to get something
that sort of looks like the real thing, at least in appearance.

IF you understand the principles around which beams are designed
it is trivial to make a homemade beam that is better than
a pre-manufactured I-beam. Instead of an OSB web, join
the flanges with plywood sides instead of a 2x3 flange, use a
2x4, instead of #2 SPF, use #1 hem-fir. Viola, a better beam.
It will cost you more in both materials and labor, but it will be
better.

To be cost-competative the manufacturers
have to make their product as cheaply as possible while still (barely)
meeting code. They are so good at this, that the material cost of
homemade beams will almost certainly exceed the cost of pre-
manufactured beams of the same stiffness.

OTOH if you do not understand the relevant principles it is easy to
design beams that are heavier and not as stiff as the pre-manufactured
ones.

For the existing roof, it would be trivial to double the strength and
stiffness by sistering a new truss next to each old one, exactly
duplicating the dimensions and materials of the old. This is
where there may be an advantage to the do-it-yourself
approach as it will not be necessary to take the whole roof
down and rebuild it from scratch.

If that is not good enough, then probably the thing to do is to replace
the old trusses with new, designed to carry the new load. Here the
problem will not be with the roof, which OP is going to redo anyhow,
but the interior ceiling which is likely to be slung from joists that
are integral to the trusses.

Either way, the local building codes will probably require a
PE to sign off on the design. Pre-fab trusses will usually be
pre-approved having already been designed by an engineer, as
noted above.

--

FF

wrote:

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this point
in your life should come when you are about 12.LOL

I guess we didn't get the memo telling us of you and your friends'
capabilities.

There's learning, and then there's learning. You may feel you've
mastered the first, but it's obvious you need to work on the second.

I really thought I might get some practical info here, Something on the
order of "I've done that before" or the info I got from the local college
ths morning. Just wishful thinking I guess.

Every so often someone pops up on one of the construction newsgroups
and wants to do something similar to what you are contemplating.
Invariably they get the same advice. The curious thing is that the
replies come from many different people who are pros - engineers,
architects, experienced contractors, etc. - it's not always the same
people spouting the company line. Invariably, if the response isn't
quite so rosy as the OP hoped, the OP's response is, "What do you
know?!" I find that amusing.

Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

Ummm, no, those strips won't triple the strength of the trusses. They
may strengthen the chords, but chord strength alone does not make a
truss. Wherever you got that information, don't go back there for
more.

To the problem at hand:
If you're in an area that requires building permits it's a sure thing
that the building department will require sealed drawings. Since you
have some engineer buddies, that shouldn't be a problem. I'm sure your
buddies are up on the major code revisions that were implemented in the
last few years, and if not, are capable of coming up to speed. I'm
sure that they'll also realize that it's not the member strength but
the connections that will be the Achilles heel of your modified truss
design, and that adding intermediate supports to a truss that was not
designed for them can create localized stresses that are beyond the
capabilities of the original design. A quick way to make your attic
ground floor accessable.

Everyone approaches such remodeling in different ways. I'd have to see
the roof structure to make up my mind for sure, but from my
understanding of your description, I'd be more likely to wait until the
roof is ripped and add new trusses at that time. You'd have all of the
roof work done in a day or two, as opposed to many days or weeks, you'd
have a designed solution, and you'd have new sheathing. I'm sure your
buddies pointed out that the sheathing will almost certainly have to be
replaced as it will be undersized for the new load. Smart people keep
up with current events, and a couple of EEs and a PE will have
commented on the major changes in construction techniques with respect
to wind loads, uplift and required metal connectors due to recent
hurricanes. These things are a pain to deal with while you're lying
flat on your stomach reaching into the eaves, but a snap when the
sheathing is removed.

I think it's great that you want to do the improvement, and that you
would like to learn how to do it yourself. These are admirable traits.
Another admirable trait is to not dismiss the people you have asked to
help you. It's kind of like insulting the waiter before your food
arrives - not a good idea.

R

RicodJour wrote:
wrote:

Obviously you dont know the capabilites of my friends or me. If we dont
know we learn. We really hate spending money for not knowing. That is the
one thing we have in common. Im sure my EE friends will let me know if they
cant handle it. They are at the point in their lives where they can learn
something new for themselves without taking a class. My dad said this point
in your life should come when you are about 12.LOL

I guess we didn't get the memo telling us of you and your friends'
capabilities.


Have you ever met an EE who didn't _think_ he understood every
other engineering discipline?



Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

Ummm, no, those strips won't triple the strength of the trusses.

Sure they will, if he sisters enough of them (like built up to about 4"
thick) alongside all of the existing 2x4 members in the present
trusses.

That certainly wouldn't be my first choice about how to do it...

--

FF

wrote:
RicodJour wrote:
wrote:


Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

Ummm, no, those strips won't triple the strength of the trusses.

Sure they will, if he sisters enough of them (like built up to about 4"
thick) alongside all of the existing 2x4 members in the present
trusses.

Notice how the OP didn't mention the connections, gussets nor anything
else? If he bolted 1/2" by 3 1/2" steel plate to the existing truss
members it wouldn't triple the strength of the trusses. The weak
point, the limiting factor, is the existing gang nail plates.

R

RicodJour wrote:
wrote:
RicodJour wrote:
wrote:


Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

Ummm, no, those strips won't triple the strength of the trusses.

Sure they will, if he sisters enough of them (like built up to about 4"
thick) alongside all of the existing 2x4 members in the present
trusses.

Notice how the OP didn't mention the connections, gussets nor anything
else? If he bolted 1/2" by 3 1/2" steel plate to the existing truss
members it wouldn't triple the strength of the trusses. The weak
point, the limiting factor, is the existing gang nail plates.


Yes but I assumed he wasn't so ignorant as to assume that
a series of unconnected segments would add strength to the
trusses.

He may be thinking about adding them to make a T- section,
rather than sistering them. That might do what he wants,
provided he joins them all properly where all the pieces
intersect but it would be a major pain compares to just
sistering them. Sistering them with 2x6 (properly connected
with nailers might triple the strength too, keeping in mind
that by nailing the 2x6 to the existing 2x4 (again with
proper connections at the joints) they become
one truss, not two trusses sharing the
load unequally due to unequal stiffness.

--

FF

wrote:
RicodJour wrote:
wrote:
RicodJour wrote:
wrote:


Went to test my box beam(built it this AM) at local junior college and found
my box beam plan was way overkill. While I didnt get to test it(forgot it
was Spring break), I did find out that just adding 3-1/2" OSB strips will
more than triple the strenght of the existing 2x4 trusses. Now to find out
the load of the shingles compared to the concrete tiles.

Ummm, no, those strips won't triple the strength of the trusses.

Sure they will, if he sisters enough of them (like built up to about 4"
thick) alongside all of the existing 2x4 members in the present
trusses.

Notice how the OP didn't mention the connections, gussets nor anything
else? If he bolted 1/2" by 3 1/2" steel plate to the existing truss
members it wouldn't triple the strength of the trusses. The weak
point, the limiting factor, is the existing gang nail plates.


Yes but I assumed he wasn't so ignorant as to assume that
a series of unconnected segments would add strength to the
trusses.

I am with you on giving people the benefit of the doubt...on matters
that won't cause big problems. On those matters I prefer to err on the
side of caution.

He may be thinking about adding them to make a T- section,
rather than sistering them. That might do what he wants,
provided he joins them all properly where all the pieces
intersect but it would be a major pain compares to just
sistering them. Sistering them with 2x6 (properly connected
with nailers might triple the strength too, keeping in mind
that by nailing the 2x6 to the existing 2x4 (again with
proper connections at the joints) they become
one truss, not two trusses sharing the
load unequally due to unequal stiffness.

The operative phrase being "proper connections at the joints". Those
are the areas where someone will run into trouble.

From an installation perspective - how would you go about getting full
length 2x6s into the attic? How would you cut them to allow fitting
around the ridge and plates?

In any event, the OP will do what he wants based on what information he
has and what he believes to be the important factors. He will then
make up his mind that he either did or did not do the right thing. If
the thing fails, well, that's clear, if the thing doesn't fail, he'll
believe that he did the right thing - whether he did or not. That's
simply human nature.

R