Therefore I'm requesting feedback on the following idea: 'Sistering' (i.e.
reinforcing with) 2x6s to the topmost rafters, followed by removal of some
of the supporting cross-members of said trusses. Not being a carpenter or
structural engineer of any kind, I'm seeking informed comments/advice from
others before going further with this.
Thanks.
Ken
"Never trust a truss" is what many firefighters say. When any of the support
members of the truss are compromised the strength of the entire truss is
compromised.
Trying to build attic space in a web of truss supports isn't going to be
easy. You'd probably have a safer project if you just put your shelving
boards in the spaces on the trusses where possible. You don't want to start
cutting on any truss. I believe there are issues with doing anything to stop
the flexing of the bottom member of the truss (probably the ceiling joists
for you). There needs to be some room for movement with temp and humidity
fluctuations.
What you are suggesting would require re-engineering of each and every
truss you are killing. All the parts of a truss work together so if you
eliminate one, you have in essence eliminated them all.
--
Joseph Meehan
Dia duit
Ken,
Work with a truss manufacturer and their truss engineers. They have truss
design software that can run your project inside out and upside down. A
normal engineer can do it, but the truss manufacturers have the software to
work up calcs easily.
You might have to pay for this engineering, since you are not buying a truss
set.
David A.
NIX on the sistering.
Truss calculations are figured from the bottom of the truss. Just how much
weight are you planning on adding? any significant weight on the top of the
truss can spell disaster.
I use my attic to store empty boxes that are broken down. total weight,
maybe 50 pounds spread out over a 4x8 sheet of plywood.
Ken:
STOP!!!!
What you are suggesting is a recipe for disaster.
1) It is quite likely that the trusses were NOT designed for attic
storage.
2) Cutting any truss members will void any warranty that the truss
manufacturer may have given or may be implied in your state law. In
other words if the roof collapses, you will have no legal recourse.
3) Rent a storage locker. It will be cheaper and much much safer.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
Tom:
Most likely they won't take the time to deal with it. This is a common
problem, but the truss manufacturers don't really want to deal with a
homeowner on a single project where they are not going to sell anything.
The possible profit to them is too small, so they won't consider it.
This is especially true if the existing trusses are not ones that they
built in the first place.
Most structural engineers (including me) don't really want to be
bothered with this type of problem either. The liability is high for a
very small return. I'd do it for a regular client, but only then. The
cost of engineering services to analyze the truss and its connections,
then design a fix is simply not worth the money in my view. You could
rent a lot of storage space or buy and build a small storage shed for
the same amount of money.
A manufacturer will probably not even give you the time of day.
And I doubt they have a CAD system and/or expert that does finite
element analysis on the stuff they do make.
Look. They churn out the same stuff day in and day out. They're not
going to have expensive computer software (and an even more expensive
engineer) on staff to basically twiddle his fingers. They don't
change their designs often enough to warrant that sort of cost. Wood
trus engineering was worked out decades ago. It's not rocket science.
For liability issues no-one is going to look at your drawings and give
you a thumbs up or down.
If you're a half decent carpenter and you throw enough 2x4's at it,
you'll probably end up with something stronger than you started with.
If you use 1/4 bolts with fender washers and (or) #12 or #14 wood
screws and pre-drill the holes (and not nail anything together) you'll
have something stronger than the existing framework.
I bet your existing wood is full of splits because of the hack job
that is usually done when cutting rafters and pounding over-sized
nails in.
Do yourself a favor and make sure each and every rafter space is
ventilated out to your soffit overhang. Don't stuff the insulation in
there - let it breath.
You are joking aren't you???????????
Most residential trusses are designed to hold up the roof and the drywall.
Attic junk not included. Floor load not included.
Colbyt
Some Guy wrote:
> > You could rent a lot of storage space or buy and build a small
> > storage shed for the same amount of money.
>
> If you're a half decent carpenter and you throw enough 2x4's at it,
> you'll probably end up with something stronger than you started with.
>
> If you use 1/4 bolts with fender washers and (or) #12 or #14 wood
> screws and pre-drill the holes (and not nail anything together) you'll
> have something stronger than the existing framework.
>
> I bet your existing wood is full of splits because of the hack job
> that is usually done when cutting rafters and pounding over-sized
> nails in.
<snip>
Now I have seen some bad advice in this forum before but this ranks
right up there with the worst of them.
Harry K
>> It would certainly
> make
>> my attic storage efforts easier if some of these cross-members could
> somehow
>> be removed out of the way (that is... in such a way as to not compromise
> the
>> structural integrity of my roof, of course).
>>
>> Therefore I'm requesting feedback on the following idea: 'Sistering'
> (i.e.
>> reinforcing with) 2x6s to the topmost rafters, followed by removal of
>> some
>> of the supporting cross-members of said trusses. Not being a carpenter
>> or
>> structural engineer of any kind, I'm seeking informed comments/advice
>> from
>> others before going further with this.
Crazy idea. Sure, there may be some method, but do you really trust a bunch
of us crazies on a newsgroup to tell you how to re-do your roof support?
Only way to know is to have a qualified engineer look at the situation. Not
knowing the spans, load, new floor load, etc, you can be in real serious
trouble with this.
I wouldn't bet on that. The odds of him messing up the structure are
very high.
> If you use 1/4 bolts with fender washers and (or) #12 or #14 wood
> screws and pre-drill the holes (and not nail anything together) you'll
> have something stronger than the existing framework.
Stiffness attracts load. You stiffen up one section of the truss and
another area, maybe on the opposite side of the house, will have its
loads drastically affected. You're intentions are good, but you're not
helping this guy.
> I bet your existing wood is full of splits because of the hack job
> that is usually done when cutting rafters and pounding over-sized
> nails in.
The house is built with trusses. No one was cutting any rafters. And
the trusses are, dollars to donuts, held together with the gangnail
plates.
R
I have to add my professional opinion that this is very bad
advice. There is no way that I would give any advice on
modifying trusses where the work is going to be done by
someone I don't know, much less without even seeing the
situation in person.
Trusses are built with enough strength to hold up what they
are designed to carry and no more. Even storing stuff on them
is considered to be forbidden by the engineers that I use.
One of my PEs will not sign off on a job if there is decking
down on the trusses because he knows that something is going
to eventually be stored there and he will NOT let you leave
it. For him to sign off on the job, decking must be removed
except where it is necessary to access equipment.
The thought of modifying trusses is not a scary thought to me,
because I have done a lot of work that involved modification
and I have worked with a lot of engineers on what to do, and I
have 30 years of experience in construction. The thought of
advising someone else on doing it sends chills up and down my
spine.
Like the time I went to look at a job where the garage trusses
were failing and looked in the attic to see ENGINE BLOCKS
stored up there! I got the heck out of that place as fast as
I could.
--
Robert Allison
Rimshot, Inc.
Georgetown, TX
> You are joking aren't you???????????
> Most residential trusses are designed to hold up the roof and the
> drywall. Attic junk not included. Floor load not included.
I guess that explains how I can load my roof with 120 bundles of
shingles and 5 guys (and that's in addition to the weight of the
existing shingles).
Cut a few truss members and try it. That's what the OP was proposing.
Most roofers I've seen at least make an attempt to spread the load out
some. If you pile all 120 bundles in one place then a roof failure
would not be unexpected.
As for the 5 guys, I assume they are moving around and not sitting in a
bunch having a smoke. That makes them "short-term" load and wood is
pretty forgiving for that type of loading.
The truss is designed to be toploaded. If you put that same load on
the bottom chord of those same trusses they would fail.
Trusses are the most economical use of wood possible. Why do you feel
that they would build in all sorts of reserve strength (and give it
away)?
R
The chords tie the joist to the rafters in a typically angular fashion.
These are mutually supportive of both the joist and the rafter.
Trusses are designed to provide a minimum ceiling load as is. Especially
the exclusive 2X4 type. I wouldn't trust these without the chords in place.
A long run over a bedroom, living area etc is inviting disaster for storage
purposes in the attic. You cut the chords, and its an even worse situation.
Conventionally framed roofs with ceiling joists of adequate width meant for
storage is probably the only type one can safely store your stuff in the
attic. A few truss designers will design these if the ceiling load specs
are provided by the builder, but its not seen very often.
"Ken Moiarty" <kmoia...@shaw.ca> wrote in message
news:BYdwe.1819374$Xk.1125184@pd7tw3no...
This really has no idea what he is talking about.
While truss manufacturers will do some business "churning out the same
stuff" for subdivision builders, they also do a substantial amount of
work for custom built homes that are one-off projects.
As one who had to source out a truss manufacturer for our custom built
home with some rather unique roof components, they most certainly do
have this sort of capability.
Now, whether they would bother with looking into an alteration issue
as the original poster has, is a whole different question.
--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
-------------------------------------------------------------------------
NOTE: if replying by email, remove "remove." and ".invalid"
The trusses have some extra load capabilities. Afterall, they must
support workers up there moving around.
That said, many peoples' attic crap can easily exceed that capability
quite quickly!
Oh, come on, it's easy. The proper way to modify a truss for
load bearing is to run posts up between the existing trusses,
put beams across just over the top, and build a deck on the
new beams. No problem. You can ADD anything you
want, you just can't take anything out, and nothing that
you add is allowed to touch the existing system.
--Goedjn
Huh? Virtually any truss manufacturer will design and supply
attic trusses for "bonus space". It's not exactly a complicated
or new problem. The problem is that if the truss *WASN'T* designed
for that, then it's almost certainly because the system can't
be easily modified to do it, else they WOULD have, when it went in.
And in someone else's post:
>>Attic junk not included. Floor load not included.
>
>The trusses have some extra load capabilities. Afterall, they must
>support workers up there moving around.
Work that through again... If the truss has, say 500# of excess
temporary support ability, because you need that for workers,
and you use that extra 500# for storage, what happens when the
workers show up?
Which doesn't solve OP's problem of limited access which is the whole
point of the thread...
I didn't mention the design load for one nail over because I did not want
some fool trying to figure out how much attic junk that equaled.
It all comes to down to weight distribution and time.
Modify a truss or two the house most likely won't cave in. Over time you
may have some serious problems.
Your house, do as you wish. I won't help you do it by giving you risky
advice.
Colbyt
Better think again
>
> Look. They churn out the same stuff day in and day out. They're not
> going to have expensive computer software (and an even more expensive
> engineer) on staff to basically twiddle his fingers.
Wrong again
They don't
> change their designs often enough to warrant that sort of cost. Wood
> trus engineering was worked out decades ago. It's not rocket science.
Wrong again
stretching my memory of wood structures class......
the allowable load for temp load was 133% of normal. Impact was 200%
> For liability issues no-one is going to look at your drawings and give
> you a thumbs up or down.
That's what civil engineers are _for_.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
The result. The roof was fine but the floor was sagging. There was
about a 4" sag from the floor was originally(in the center)
Eitherway, knowing that a house is usually someones largest asset, do
you really want to compromise its value by cutting corners. Either
find an engineer or find a different space to store clutter.
c_kubie
Sure. You just have to find one willing to do so.
As I said before, this is not cost effective. The price a homeowner is
willing to pay for services is not commensurate with the liability
exposure.
Are you willing to pay more than $1000 so you can store some stuff in
the attic. If you are, then I might consider doing the work.
The civil engineers that I use don't do structural.
Rant: For a home that sold for hundreds of thousands of dollars, you'd think
the builder could've been a little more liberal budgetwise and built the
house to higher spec.
Ken
There is such a thing as an "attic truss". But, it must be specified at
the time of design and manufacture. Typically, the truss is designed
with an aisle way down the middle and the bottom chord is designed to
carny the weight of stuff stored in a typical attic.
The engineer or architect can specify a heavier than normal load on the
bottom chord. Obviously, the truss manufacturer will do what's typical
unless told to do otherwise. the spec building could specify an attic
truss, but that costs more. Most spec builders on not going to spend
the a few hundred extra dollars if they don't have to.
Most of the older homes that I've seen don't have such beefy floors.
Most of them have 2x6 ceiling joists or even 2x4s.
>Then the roof is 2X6's
> from the outer walls, and come together at the peak. Built that way,
> you can make a real attic, build rooms up there and whatever.
Sure, if the home is built the way you say.
>Trusses
> save the expense of the larger dimension lumber, but are all wasted
> space. They are fine for a barn or something where you would not need
> an attic, but for a house they are just a big waste of space.
Trusses can be, and are, designed for all sorts of conditions and
loads. I frequently have to beef up or replace existing stick frame
structures when remodeling. If it wasn't designed for it, it has to be
modified. The only difference is that trusses are more complicated to
analyze and therefore modify.
> Considering the high cost of trusses, I tend to wonder if they are
> really worth the savings, because I tend to think the savings is
> minimal.
Every tract home builder in the country disagrees with you. There are
many advantages - much longer spans possible eliminating the need for
interior support and concomitant foundation costs, faster roof framing,
weight savings, etc.
> As for your situation, I can only say this. You cant just sister
the
> roof joists, because the floor could drop (along with your ceiling
> below) However, if you were to sister 2x8s across the floor, AND
> 2x6's on the roof, being sure both the 2x8's and 2x6s are resting on
> the outer walls, and on the center support wall of the home, you could
> probably get away with it.
If he's just looking to add storage capabilities (floor load), why does
he have to touch the roof? He could ignore the trusses and install
floor joists next to them, but if he doesn't have a center support
wall, he probably can't do that.
>Look at the way an older home roof was
> built, and duplicate that. But, if your trusses are 2x4s, you may not
> be able to get your new wood onto the outer walls, unless you can cut
> the angle and still have enough wood on the walls. I am not
> suggesting you do this without having a professional engineer or
> builder look at it, but it could possibly work. Your other option
> would be to remove the entire roof and rebuild it using stick
> construction, but I dont think you want to go that extreme.
Probably not.
> As someone else said, trusses are not made to hold heavy loads, as a
> floor. Those 2x4's are likely spliced right in the middle of your
> rooms below, so even if you leave the trusses intact, I would still
> add some at least 2x6's from outer walls to center walls and floor on
> top of them.
You are advising that substantial loads be placed on walls that may not
be bearing walls...?
> Of course you could move too....
> Remember, many of the older stick built houses have lasted a hundred
> years or more. These new houses built out of crap have a life
> expectancy of about 30 years. So you might save a few bucks today,
> but you will pay and pay and pay later.
Not sure where you got your life expectancy number from, but it's
_extremely_ pessimistic.
R
> If he's just looking to add storage capabilities (floor load),
> why does he have to touch the roof? He could ignore the trusses
> and install floor joists next to them, but if he doesn't have a
> center support wall, he probably can't do that.
Look what the original poster (OP) said:
"Currently I'm busy fastening 3/4" plyboard over the ceiling
rafters (so objects to be stored won't crash thru the drywall
ceiling)."
So we can assume that the rafters are strong enough to support someone
wiggling around putting plywood down?
3/4 plywood to tie the rafters together will certainly give some
additional strength to the load-bearing capacity.
What for? You bought it anyway...
It's adding a substantial load just sitting there and it's overkill.
It will help spread out load, it won't add to the overall capacity.
R
That's the problem - the builders brag about meeting minimum standards (as if
that's an accomplishment) and then people buy them regardless. Price comes
before quality as usual.
Mike
And, "what the customer doesn't know won't hurt him..."? Uh huh. I used to
work in floor covering and dealt with many a commission salesman... Talk
about tunnel-vision! You can recite any of the litany of self-serving
excuses all you like. I've heard them all before.
Ken
I don't think Goedjn was commenting on the morality of doing inferior
work - not that trusses are in and by themselves inferior, but more
that the OP didn't have to buy the house in the first place. If he
needed attic storage, he should have bought attic storage or insured
that it was doable on his budget. If he didn't do the homework, he
shouldn't hold it against anyone but himself.
R
Well, you can get trusses designed to provide attic space.
Matt
> I realize trusses go up
> faster, but normally a crane is needed to lift them to the roof, and
> renting or owning and running that crane adds to the cost of the
> labor. Stick construction just requires some men to lift the boards.
Pick-up-sticks construction? They don't just lift them, they have to
put them together. That takes time ($$$). Even with the cost of a
crane, there's no way that hand-built roofs in the field can be cheaper
than factory built roof trusses unless you're talking about building
_one_ house with cheap labour.
Mike
> They MUST be load bearing walls. In most homes the wall down the
> center of the house IS the load bearing wall. The way to find out is
> to see if that wall is on top of the support beam in the basement.
Maybe where you live, but I've seen lots of bungalows built with a
centre support beam holding up the floors and full span roof
trusses. The centre wall in those cases is not load bearing.
Mike
I [the OP] didn't take him to be commenting in any way on "morality" in
any way. My comment was simply to convey my personal distaste for
builders and/or other vendors, even other consumers, etc, who are just
plain "cheap". IOW, what's wrong with a little "class"? I will accept
however, that most people don't care to possess much in the way of this
quality. So I am well out-voted by the majority here.
Ken
How does "class" enter into it? I'm not sure what you could mean by
that. Do you mean that a builder should just throw in all sorts of
extras and upgrades for free to show he has class?
You wrote:
"Rant: For a home that sold for hundreds of thousands of dollars, you'd
think
the builder could've been a little more liberal budgetwise and built
the
house to higher spec."
The builder didn't set prices for the materials he bought, the
subcontractors he used, the land in your area, etc., etc. He set the
sale price for the house based on what he thought the market would
bear. If he, or a subsequent owner that you purchased it from, had
priced it higher you might not have bought it, or it might not have
sold at all. It's a balancing act. If the builder was a fly by night,
or cut every imaginable corner, this should have shown up when you were
doing your research.
Since you bought the house, you must have felt it was a good value at
the time, based on your research into the housing market in your area.
>From your personal distaste comment above about cheapness, you couldn't
have been afraid to spend the necessary money. So how did the building
all of a sudden become cheaply made?
Obviously it didn't change from when you had it inspected and made your
offer. You did have it professionally inspected, right? If the house
is as shoddily built as you say, I'm surprised that the inspector
didn't steer you away from the house you're in.
I'm not sure if this is the first home you've bought, but it sounds
like you've come to realize that you now have higher expectations for
your house, and have learned more about how houses are built.
Looking on the bright side, with the market the way it is, your house
is probably increasing in equity value fairly rapidly - regardless of
the way it was built.
R
Ken
"RicodJour" <rico...@worldemail.com> wrote in message
news:1120287396.3...@g44g2000cwa.googlegroups.com...
Ken
"John Willis" <jdwill...@airmail.net> wrote in message
news:moadc1dup48lkjs1h...@4ax.com...
> On Sat, 02 Jul 2005 07:37:11 GMT, "Ken Moiarty" <kmoia...@shaw.ca>
> scribbled this interesting note:
>
>>
>>"John Willis" <jdwill...@airmail.net> wrote in message
>>news:u7nac1p6pq19d5bb3...@4ax.com...
>>> [...]
>>>
>>> Really? Seems you fail to understand that as with any business these
>>> days, accounting is what actually runs it, not the quality control
>>> department!:~(
>>>
>>
>>Accounting is just a tool. As with any tool, the tool itself doesn't
>>determine what your mix of priorities are to be. "People", with their
>>objectives, interests, values, aspirations and desires etc. ultimately
>>determine that. If the people don't enter "quality control" into their
>>accounting equations, it is 'people' who have chosen to not do so, not the
>>'science of accounting'.
>>
>>You seem to imply that "quality" is some kind of silly, superfluous,
>>entity,
>>which is non-essential to productive business activity. Though I expect
>>no
>>shortage of, say... overpaid government bureacrats, slick talking used-car
>>salesmen, or back street drug dealers, etc... who'd likely be eager to
>>agree
>>with you, I for one beg to differ!:~)
>>
>>Ken
>>
>
> Sorry if what I said seemed to imply what you inferred. It was not my
> intention. The point being exactly as you made it. The lack of quality
> is caused by a short term focus on one portion of the equation, that
> being the bottom line at the end of the day, instead of the end of the
> decade. It is an unfortunate state of affairs that the "Wal-Mart"
> syndrome is everywhere...
>
>
> --
> John Willis
> (Remove the Primes before e-mailing me)
> > That's what civil engineers are _for_.
> The civil engineers that I use don't do structural.
Maybe a terminology difference. Here, I believe there isn't
a "structural engineer" designation per-se, it's a specialty
in civil. My dad was a civil, and he did structures, tho,
his main work was in other stuff.
If you time your truss delivery properly, then the delivery driver will
lift them onto the roof for you. All you need to is roll them up and
nail them down.
The designation of "civil" vs "structural" engineer will vary by state.
The requirements for becoming a "Structural" engineer also vary by
state.
In Washington State, you must be a licensed PE (civil, mechanical,
mining, etc.) before you are allowed to sit for the structural exam.
A summary of requirements goes like this:
1. 4 years college or appropriate work experience
2. Take and pass the Engineer-in-Training exam (8 hours)
3. 4 years work experience for a total of 8 years counting college
4. Take and pas the PE exam in an appropriate discipline (usually civil)
5. 2 more years work experience
6. Take and pass the NCEES Structural I and II exams (16 hours)
7. Take and pas the Western states seismic exam (8) hours)
So to be a licensed structural engineer in Washington State you must
have the following minimum requirements:
a. 10 years appropriate work experience
b. take and pass 32 hours of examination
Exactly. Not of much help to the OP, but that's the way to do it. I have
just completed the rebuild of a total ground up rebuild of my home that was
lost in a fire. The original home (50 yrs old) had a stick built roof and
was considered to be in the premier neighborhood in the area at the time.
The construction was what I would rate as average, although contractors who
examined what was left said it was very well built. 2x6 outside walls,
plaster walls, mahogany trim, etc. Attic access was through the garage. 2
X 8's on 16" centers spanning 24'! Most of the plaster on the garage
ceiling was cracked due to sag. Didn't store too much other than christmas
stuff and empty boxes. Still, just my weight (170lbs) you could feel the
joists move. In the new house, I had the garage (increased to 35') area
trussed for storage (the truss people like to call it a "bonus room").
Solid as rock! I can literally jump up and down and the floor/ceiling
doesn't give a bit! So much for old vs. new construction. Could a free
rafter roof be as solid? Sure, I have no doubt. Lot's more expensive
lumber. The big bonus as far as I'm concerned with trusses is the future
flexibility with floor plans. Want to move a wall? No problem. Most
interior walls are non-load bearing so just knock 'em down and move 'em. As
far as the "particle board" I-joists, I doubt a toilet over flowing once (
or even a dozen times) is going to dissolve them. And if you've got that
bad of a water problem, you've got some serious problems! They got a bad
rap early on, but the adhesives have vastly improved in the last ten years.
A good analogy is the world of automobiles. Once upon a time, to build a
solid car, you added more metal. Now, look at the most structurally solid
cars. What do they use? Carbon fiber in honeycomb EPOXY matrix. Yeah,
they're glued together! Try to field a formula one or indy car out of good
old fashioned steel and see where you get. Technology marches on. If you
use it wisely, you can build a very solid house. However, I am convinced
after working early on in the design phase of my home that your typical GC
doesn't give a hoot about quality. If you want a well built house (or
anything else, for that matter) you're better off building it yourself.
That's what I had to do.
--
JerryD(upstateNY)
Well, it COULD be done, but it would be expensive as you'd need glulam
or other engineered lumber for the joists and rafters. :-)
Matt
>I just built a house and used trusses because I have a floor plan with the
>kitchen/dining/living room all open.
>There is a 32' open span that couldn't be done with ceiling joist/rafters.
My garage has a 32' clear span and I did it with I-joists. Plus, I
put them up singlehandedly.
Amputee? ;)
R
No, one hand on the ladder, one hand pushing the joist into the
hanger. :-)