Repairs Made to Damaged Roof Trusses

[Nick Ostrowski]

The townhome I looked at yesterday had 6 cracked roof truss members that had been sistered or repaired in some fashion and two others that were cracked and in need of repairs. I advised the client he would need a rep for the truss manufacturer or a structural engineer to design appropriate repairs for the damaged trusses that have not yet been repaired and that the same person should also inspect the repaired trusses to determine whether or not the repairs are adequate.

I have no idea what is an appropriate repair for these trusses but I know some of the work doesn't look like it was designed by an engineer.

[Rick Cantrell]

Those are some sorry looking trusses. I can't remember seeing any trusses with knots that big and so many knots in them. It's no wonder they cracked.

[John Kogel]

I'll bet they were damaged before they were put up, by sloppy handling.

If there is any warranty remaining on that townhouse, it should go back to the builder. Structural defect. There may be other units in the complex with similar kaka handywork.

A typical engineered repair involves big plywood gussets and plenty of carefully placed nails. You made the right call, IMO.

[Nick Ostrowski]

I'll bet they were damaged before they were put up, by sloppy handling.



My thought was that the trusses were dumped off the flatbed in unceremonious fashion. But the amount of knots on the truss members definitely do not help.

[Eric Barker]

I know some of the work doesn't look like it was designed by an engineer.

Nothing like a good 'ol gut feeling to steer you right.

[Kristi Silber]

That's crazy! How did it happen - snow load? They couldn't have been installed like that surely, it would never pass inspection. I'm surprised it did anyway, with trusses like that. Is there just one center 2X6 for webbing? What's the span? Totally irresponsible contractors.

[Randy Mayo]

I am in agreement with Rick. I have never seen such low quality lumber used in a manufactured truss. Around here you very seldom see any knots. If they were cutting corners on material what else are they cutting out?

[Thomas McKay]

WOW that is terrible; guess I will have to stop looking for a townhouse in Philly!:(

[Stuart Brooks]

That's crazy! How did it happen - snow load? They couldn't have been installed like that surely, it would never pass inspection. I'm surprised it did anyway, with trusses like that. Is there just one center 2X6 for webbing? What's the span? Totally irresponsible contractors.

The inspector would have to actually look up to see the damage. Not many bother in my general area. I actually ran across one a couple of days ago that was trying to be thorough. He actually asked mmy opnion on fire stopping an area. I had to find a wall to lean on. I was totally flabbergasted.

[Harry Janssen]

I would recommend that any repairs be approved by an engineer,as the original truss was approved by same.

[Kristi Silber]

The inspector would have to actually look up to see the damage. Not many bother in my general area. I actually ran across one a couple of days ago that was trying to be thorough. He actually asked mmy opnion on fire stopping an area. I had to find a wall to lean on. I was totally flabbergasted.

It sure has been eye-opening hearing about the shoddy work some public inspectors do. That must vary considerably from district to district, depending on the oversight, communication, and expectations of the inspections departments generally. Scary to think that not just property, but also lives depend on these poorly-trained/lazy people.

[Thomas McKay]

It sure has been eye-opening hearing about the shoddy work some public inspectors do. That must vary considerably from district to district, depending on the oversight, communication, and expectations of the inspections departments generally. Scary to think that not just property, but also lives depend on these poorly-trained/lazy people.

Yea they work for the local or state government, make more money than you do and have a free benefits package including retirement. Go figure! :eek:

[Raymond Wand]

Found this, which I thought was interesting on knots. If these are engineered products then surely the knots and quality of wood would have been taken into consideration at the design stage by the engineers?

Powered by Google Docs (http://docs.google.com/viewer?a=v&q=cache:9ktsIIMvH_0J:www.wbdg.org/ccb/NAVFAC/OPER/mo111_1.pdf+knots+in+roof+truss&hl=en&gl=ca&pid=bl&srcid=ADGEEShfzH6_elK6VXc_etdBBY72PuO3ntn-0xh55okSkw3UsDeoM5CiJzbwwY0cV41GTzJXlvTmh3ps5-VXrM0eV96wD-AiweN8o1Mqp7NQPcK6eHVuGE0DpQWd6ChIC0icMTbDAOBV&sig=AHIEtbTpkKGliYreE2tVILG1fLwjWuu_lQ)

Inspection of wood beams and trusses


1.2.1-B QUALITY. Within a species, a high-quality piece may have twice
the strength of a low-quality piece of comparable size. The principal features
affecting the strength of lumber are knots, cross grain. and checks or splits.
The effect of a knot depends on its size and location together with the type
of strength property being considered. The strength reducing effect is generally
in direct proportion to the portion of the cross section occupied by the knot or
to the portion of the width of the surface in which the knot appears. Knots near
the bottom edges of members loaded in bending have about twice the strength-
reducing effect of those located elsewhere. Knots near the ends of beams have
little effect on the strength. Compressive strength is reduced only about half as
much as are tensile or bending strength. Knots have only a small effect on lumber
stiffness. Since the principal effects from knots are in the distorted grain around
the knot, loose knots or knotholes are generally considered to have about the
same effect on strength properties as intergrown knots of the same size. Knots
have no significant effect on bearing strength (compression perpendicular to grain)
or shear strength.Also
Inspecting Wood Trusses | ASHI Reporter (http://www.ashireporter.org/articles/articles.aspx?id=1213#Fig-09.gif)

[Jerry Peck]

Yea they work for the local or state government, make more money than you do

In some areas, the inspectors may be paid well, but even in areas where the municipal inspectors are paid well (and not all areas pay well), a good home inspector, in decent times, would make A LOT more money than the municipal inspectors. In tough times, yeah, the inspectors who are left (many have been laid off) still make a the same as they did before.

Keep in mind, though, that not areas pay their inspectors well.


and have a free benefits package including retirement.

Yeah, if you work there for 30 years ... 20 years does not get them much of a percentage, and anything less than 20 years doesn't help much.

Also keep in mind that there are good and bad home inspectors, just like there are good and bad municipal inspectors.

I can only speak from the areas that I have worked in, and the good municipal inspectors are far more prevalent than the bad ones, just like the good home inspectors are far more prevalent than the bad home inspectors, but it is the bad ones you hear about and remember.

Yesterday I spent 2 hours at a framing inspection, the builder agreed that the truss engineer had to come out and go over the entire roof system and floor system as they specified one type of hanger and provided a different type; specified one type of bearing for top bearing floor trusses which was impossible to do on this structure and now have to approve what was done or design and affect appropriate repairs for them; the hangers provided did not have enough nail holes; the list goes on and on, but the end result is that the truss company and their engineer are going to have to eat the redesign and repairs, which may become quite costly.

Regarding having inspectors look up ... the framer said this to me: "Your neck must get tired and sore looking up all the time.", to which I replied "Yes it does, quite sore at times."

When making general comments about "bad" code inspectors keep in mind that there are "bad" home inspectors too.

This information is for those who seem to think that I spend all my time in a courtroom ('they' know who I am referring to :p ) and have no on-site inspection experience or real world understanding of what goes on - *almost all* my time is spent in the field as a "First Preventer" ... trying to keep the First Responders from having to respond later.

[Kristi Silber]

Jerry, you better post your field experience in an electrical thread if you want *some* people to know about it.

Half the people in any profession perform below average! Just a matter of what the average is.

[bruce audretsch]

Those knots in the second photo should never be in an engineered truss member.
I think these were home-made.

[Raymond Wand]

My thinking is these trusses were damaged during delivery. Repairs conducted onsite.

Also

A great guide

Building Component Safety Information
Guide to Good Practice for Handling, Installing, Restraining & Bracing of Metal Plate Connected Wood Trusses

Building Component Safety Information (http://www.sbcindustry.com/bcsi.php)

[Thomas McKay]

Jerry, who was talking about bad home inspectors; I thought the conversation was about defective trusses and the possibility they were missed by the building inspector? Your comments don't really equate! :confused:

[Darryl Grimaldi]

In most states, if a truss has been inspected by a structural engineer or the truss manufacturer and repairs made based on their recommendations, there will be a stamped repairs spec sheet stapled to the repaired trusses. Some states have the truss manufacturer or engineering firm actually stamp the repaired truss. If none of these are present, the repairs have not been made by truss manufacturer or in consultation with structural engineer.

[Larry Morrison]

In most states, if a truss has been inspected by a structural engineer or the truss manufacturer and repairs made based on their recommendations, there will be a stamped repairs spec sheet stapled to the repaired trusses. Some states have the truss manufacturer or engineering firm actually stamp the repaired truss. If none of these are present, the repairs have not been made by truss manufacturer or in consultation with structural engineer.
That is exactly the case where I am. Normally it is the truss manufacturer that makes the repair on site. A sticker is placed at the repair and an addendum is added to the truss documents.

[Jerry Peck]

It sure has been eye-opening hearing about the shoddy work some public inspectors do. That must vary considerably from district to district, depending on the oversight, communication, and expectations of the inspections departments generally. Scary to think that not just property, but also lives depend on these poorly-trained/lazy people.


Yea they work for the local or state government, make more money than you do and have a free benefits package including retirement. Go figure! :eek:


Jerry, who was talking about bad home inspectors; I thought the conversation was about defective trusses and the possibility they were missed by the building inspector? Your comments don't really equate! :confused:

I think you must have missed those two posts above, re-read my post and I suspect you will see where my post fits in with those comments above.

[Tom Huling]

I think the advice to contact the truss manufacture is the appropriate way to approach this situation. Truss manufacturer's expect situations like this, it happens all this time.
In reality, the truss manufacture would rather resolve an issue like this for minimal cost as opposed to face litigation on a catastrophic failure.
The repairs are pretty straight forward , using the correctly sized structural member, plywood/OSB gussets, a correct nailing pattern and nail size and construction adhesive. Again the repair is to be designed by the truss manufacture!
To kind of set the record straight on how the home building business works regarding truss systems. The builder/developer will submit their architectural plans to the truss manufacture for engineering on the roof truss system. With a pretty sophisticated software program, a designer will enter all of the given information regarding the particular structure.
The elements considered are the live and dead loads, any concentrated loads and wind and seismic criteria and any special connection requirements.
Most all reputable truss manufacture take the business very seriously, with everything being supported by a structural engineer.
In regarding this particular roof system a couple of things pop out at me.
The one photo has a bracket attached to the vertical member and the fire wall and the other photo with the split horizontal chord, I think a safe bet would be that damaged on installation.
However, the photos that show broken vertical chords indicate something else was going on to cause the breaking. I'll admit the size of the knots is not a pretty sight. but if my memory serves me right there should be a grading stamp somewhere on the wood components and it should read something like #2SPF, which should be acceptable for these components(if there is a truss designer out there to correct me, please do so).
What I think caused the failure is there was a concentrated load set on the peak of the roof, i.e. shingles.
When shingles are delivered to the job site, it is common practice to "spot" the bundles on the peak of the roof. I'll be conservative on this example. If you figure that one bundle of shingle weighs about 50#'s. and lets say that 15 bundles (5 squares) are concentrated on two trusses, that is 750#'s dead load at that point. The metal plates are designed to move with the loading, but in this situation, when the vertical wood component went into compression, that big ugly knot couldn't handle it.
In regards to the speculation of the inspector not catching this wood butchering job. I would bet again that the attempt to fix this was done after the rough in framing inspection was completed.

As a final thought, there is a nice little publication title "Encyclopedia of Trusses" published by Alpine Engineered Products. Welcome to Alpine Engineered Products (http://www.alpeng.com)

[Kristi Silber]

I think the advice to contact the truss manufacture is the appropriate way to approach this situation. Truss manufacturer's expect situations like this, it happens all this time.

Really? That's a scary thought! It shouldn't happen at all! Problems like this could easily go undetected, getting worse and worse until it's too late.

I'm thinking Bruce might have hit the nail on the head - the trusses weren't made by a truss manufacturer at all. To me, from what I can see in the photos, these don't look well-designed for the span - too little webbing, perhaps to save on lumber costs. I also agree with Tom that the damage came after installation, and his idea of shingle load makes sense. However, some of the damage must have occurred later, or it would have been "fixed" at the same time as the rest.

The fact that the horizontal tie beam is cracked suggest the middle web member is transferring weight to the beam, when it should be under tension. In fact, since those vertical pieces should be under tension, it shouldn't matter as much as it obviously does that they have knots (not that the knots are acceptible anyway). It makes me wonder how the trusses are attached to the wall plates, and whether there is slippage going on. That is where the load from the roof should be transferred to; the tie beams of trusses simply aren't designed to handle it. The bracing, too, looks inadequate. SO many problems here!

[Raymond Wand]

How old is this house?

No one noted the the OSB and plywood decking. Something amiss other than the trusses.

[Nick Ostrowski]

The house was 13 years old.

What is the significance of having both OSB and plywood decking? In townhouses around here, I regularly see different roof decking materials adjacent to the firewalls (4-8 feet away from the walls). I believe there is a reason for this but I can't recall what it is right now.

[Raymond Wand]

Thanks for the info. Given it a townhouse I wonder if other trusses are damaged in adjoining attics? Not that it would be of a concern to you but out of interest.

There is great info at the site I listed earlier about placing stacks of shingle bundles on the trusses, and how they may be damaged by lifting btw and other associated issues.

Building Component Safety Information (http://www.sbcindustry.com/bcsi.php)

[Raymond Wand]

Kristi wrote in part:

The fact that the horizontal tie beam is cracked suggest the middle web member is transferring weight to the beam, when it should be under tension. In fact, since those vertical pieces should be under tension, it shouldn't matter as much as it obviously does that they have knots (not that the knots are acceptible anyway)

I think your terminology is wrong the webs and horizontal members are under shear and compression loads.

Also the knots may not be a problem as per earlier post as to knots.

[Jerry Peck]

The trusses do look like they were manufactured by a truss manufacturing company, at least to me they do.

There is no problem having fire retardant treated plywood covering the first 4 feet of the roof sheathing as 4 feet from each side of the separation wall needs to be protected.

The main thing I see with the way the plywood and the OSB were installed is that there are not staggered joints over that truss which is 4 feet away from the wall, and the joints need to be staggered.

The fire retardant treated plywood should be staggered, such as one 4' piece and one 6' or 8' piece, then another 4' piece.

[Raymond Wand]

Thanks Jerry

Good observation about the plywood not be staggered, missed that one.

[Kristi Silber]

Kristi wrote in part:

"The fact that the horizontal tie beam is cracked suggest the middle web member is transferring weight to the beam, when it should be under tension. In fact, since those vertical pieces should be under tension, it shouldn't matter as much as it obviously does that they have knots (not that the knots are acceptible anyway)"

I think your terminology is wrong the webs and horizontal members are under shear and compression loads.

Also the knots may not be a problem as per earlier post as to knots.

Since the pieces of the truss are not designed to move relative to each other the forces have to cancel out. The bottom horizontal tie (chord) is under tension - it's keeping the ends of the truss from spreading out. The webs can be under tension or compression, depending on where they are. I may be wrong, but in this case I don't see any webbing except at the ends and the single vertical piece in the middle. If that's the case, the center post should be under tension - it should not be transferring a load to the center of the tie unless there are other webs under tension to counteract that force.

I'm not sure what you're talking about when you say the knots may not be a problem. Most of the paragraph you (Raymond) quoted earlier talks about problems with knots. Do you mean, "Knots
have no significant effect on bearing strength (compression perpendicular to grain)"? That refers to things like wall plates, where the wood is horizontal, supported underneath, and bearing the weight of something else on top of it. The compression in trusses is parallel to the grain, a combination of the force of gravity and the tension in the tie beam.

[Timothy M. Barr]

I have been hanging trusses for many years and have never seen a knot more than an 1/2 in dia.. Made at the site would be my guess then handled poorly

[Douglas Mudge]

In my experiance as a framer for years before becoming a home inspector. when it comes to broken truss webs only an engineered repair would be correct. this is in many cases a 2x member scabbed to the side of the broken member that extends a certain distance on each side of the break. there is usually a required nail pattern that to me seems excessive. Looking at your photos, it appears to be a temp fix, probably to get the trusses up and then when you have to wait for enegineered repair specs , sometimes it gets forgotten. Anyway, Good Call.

[Thom Huggett]

I note 2 things in the pictures:

The king post web in the second picture has a section containing 2 large knots. I am not a lumber grader, but I don't believe that this condition meets even utility grade lumber, so I would guess that the truss manufacturer did not know what he was doing when he fabricated the trusses.
The NDS (National Design Specification for Wood Construction) requires that structural panel (plywood/osb) sections be at least 24" wide without using a correction factor. In the second picture it appears that a very narrow piece of roof sheathing (6"?) was installed at the ridge. (The NDS is a part of the IBC per section 2306).I also agree that the damage was most likely done during installation of the trusses, and fixes must be designed by a registered civil/structural engineer (IBC section 2303.4).

[Charles Gifford]

This is interesting discussion.

Good catch on the FRT Plywood and the stagger.

Living, building and inspecting in an area where roof trusses have been common since the early 60s I have had a need to understand trusses, lumber grading, truss engineering and truss plate applications.

A couple of things. In our area (NE Florida) most trusses are #2 Southern Yellow Pine. It has knots and sometimes there are lots of knots. The truss manufactures typically use machine grading and cutting. The boards are scanned and cut using computer scanning and saws that take the bulk lumber and select the best pieces and cut to the best length. The key is not necessarily the number of knots but where they are located within the length of the board. There is however specific guidance provided by the Truss Plate Institute that addresses the truss plate, the ability of the truss plate to bite into and grip the wood and the location of knots, etc.

Charles

[brian schmitt]

The trusses do look like they were manufactured by a truss manufacturing company, at least to me they do.

There is no problem having fire retardant treated plywood covering the first 4 feet of the roof sheathing as 4 feet from each side of the separation wall needs to be protected.

The main thing I see with the way the plywood and the OSB were installed is that there are not staggered joints over that truss which is 4 feet away from the wall, and the joints need to be staggered.

The fire retardant treated plywood should be staggered, such as one 4' piece and one 6' or 8' piece, then another 4' piece.
jerry,
if the joints have to be staggered, why is table 2306.2.1(1) in the ibc?

[Jerry Peck]

jerry,
if the joints have to be staggered, why is table 2306.2.1(1) in the ibc?

Notice the load reductions (which are considerable) and/or nail spacing reductions (closer spaced nails equals more nails) when the panels are not staggered.

That table is new to the 2009 IBC and allows designers more choices as long as the revised loads and/or more nails are used.

[Kristi Silber]

Is that a water mark I see up top in the second photo? Ridge nailing problems?

I don't understand why, if the damage happened during installation, they "repaired" just some of it. Is the damage grouped? And what's the span of the roof?

I also don't understand how any truss manufacturer could stay in business building such poorly design trusses with such cheap materials. Their quality is on par with the rest of the workmanship.

Which photo shows the lack of stagger? I can't tell what you're looking at.

[brian schmitt]

Notice the load reductions (which are considerable) and/or nail spacing reductions (closer spaced nails equals more nails) when the panels are not staggered.

That table is new to the 2009 IBC and allows designers more choices as long as the revised loads and/or more nails are used.
jerry,
this method of not staggering the joints has been in the APA installation guides for many,many years and in the ubc for many ,many years. Your statement is one man's opinion, not a code requirement. have a happy thanksgiving old boy:D

[Jerry Peck]

Notice the load reductions (which are considerable) and/or nail spacing reductions (closer spaced nails equals more nails) when the panels are not staggered.

That table is new to the 2009 IBC and allows designers more choices as long as the revised loads and/or more nails are used.


jerry,
this method of not staggering the joints has been in the APA installation guides for many,many years and in the ubc for many ,many years. Your statement is one man's opinion, not a code requirement. have a happy thanksgiving old boy:D

Guess it's just that this Old Boy has always seen structural panels installed staggered, guess no one wanted to REDUCE THE LOAD AND INCREASE THE NUMBER OF NAILS ... :p ... when there was no need to. :)

Regarding my previous comment about that table being new to the 2009 IBC, it is not, I just could not find it in the 2006 until I did some more searching through it - seems that it has been okay to REDUCE THE LOAD AND INCREASE THE NUMBER OF NAILS for some time now - just not sure why anyone would want to add more nails and still end up with lower load capacity, but that option seems to be in there. :p

[brian schmitt]

jerry,
not staggering is a piss poor way to build but acceptable in minimum code. I always staggered the joints for strength and it would prevent the joints in the plywood from telegraphing thru the roofing after a few years.;)