truss or retrofit?

[jweinberg]

40 year old home. Comp shingle roof. 2x4 rafters and ceiling joists...no collar ties or purlins.

1x6 web members set up in a fink truss design.....however.... no tags, and the web members are not directly in line with the rafters and joists. They are nailed outside the wood gusset plates.

I'm calling this rafters and joists with retrofit wood members added. Any input would be appreciated.

Thanks!

[Dale Duffy]

A rafter system without the ridge beam....

[Marcel R. Cyr]

Like I have always said, pictures do not give you the thousand words unless they are focused on the whole picture.

These were obviously home built trusses and the plywood gussets at the peak, were common to be 5/8" plywood as such and the first of the truss chords should have been no more than 30 degrees and this pictures show that to be exceeded. The angle should have been reduced and one more added chord on the other end.
In this Era, it was typical to use full 1" boards rough sawn usually to provided the chord bracing. I know, because that is the way I used to build them in the 60's with my father.

The chords displayed in the picture should have been opposite of the plywood gusset at the ridge. Better balance.

A ridge beam is normally used for carrying the weight of the rafters or the roof. It is then supported by end beams that carry the load to the walls below or somewhat in that order.

Pictured here is the common fink truss and possibly should have been a double fink. Just my Opinion.

I am curious at this point as to why the nails are so long and why what appears to be plywood sheathing on spaced boards.??

Marcel
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[Robert J. OConnor]

The top cords/rafters would be too small to span from the ridge to the outside walls, so I agree they look like site built trusses from the initial construction. May have been originally built that way, or modified at some point ... but that would be hard to tell.

[Marcel R. Cyr]

Robert;

I believe that these photo's indicate site built roof framing in an obscured manner to simulate the Fink Truss design. I do no see any modifications to a designed truss system. If in fact, it were a truss design, signs of connector plates would be observed. JMO

Marcel
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[Robert J. OConnor]

Originally Posted by mcyr

I believe that these photo's indicate site built roof framing in an obscured manner to simulate the Fink Truss design. I do no see any modifications to a designed truss system. If in fact, it were a truss design, signs of connector plates would be observed.

Since it was reported to be 40 yrs old I was thinking more along the lines of an older site built truss (or truss like configuration) without metal plates, as the metal plate connectors is more of a modern application.

It does look like a fink type configuration, but something does seem a bit off and I would have expected to see more plywood plates at the connections. It may have been a post type configuration (essentially like a braced rafter) with another series of members added if there were issues, as the ceiling members look a bit large for a fink truss and the wood grain on the vertical members looks a bit different from one row to the next ... but that may just be an optical delusion.

Also the connections at the bottom aren't really visible, and it's possible there are bearing walls near the connections at the ceiling that would make the braced/post type configuration a definite possibility (particulary if there are larger ceiling framing members).

It's all a WAG just based on a few photos that don't tell the whole story, and I'm really just thinking out loud off the top of my head ...

[rwand1]

I don't have any issues considering it was built 40 years ago and seems to be over built. The rafters line up and are further secured with a gusset and additional diagonal support, along with plank decking.

[lewens]

Sure looks way over built. I am curious about the need for 2x material laid on the flat on top of the rafter/truss. My grandfather often used plywood to make his own gussets when he was suspect about the ability of the rafters to carry the snow loads in the Eastern Townships of Quebec. Marcel will understand that comment.
Larry

[Marcel R. Cyr]

Hi. guys and hope you are all doing well.

Back in the 1970's, people (contractors) started simulating roof trusses that were coming out as Engineered Trusses. Since the factories were few and far between, older Carpenters caught on to the fact that Engineered Trusses were faster and more economical. They proceeded to improvise the steel connector plates with plywood 5/8" thick for gusset plates and chose to stay with the oversized lumber they were using as was normally used for stick building. Therefore, you actually ended up with an over Engineered Truss Manufactured by our Fathers of Time.

The plywood gussets were about two feet long for a 4 in 12 pitch at the overhang and three feet to four feet long on the plumb cut , depending on the estimated load, sometimes that was applied on both sides.

The Monoplaner trusses at the time would have had the first chord point at roughly 10'-11" for 2"x4"bottom chord. the angel of the fink chords were 12" rise to 3x the run. This was the basis of the home built truss design.

Since Northern Maine as well as our Canadians friends have a good shore of snow load, most rafters and ceiling joist are almost always 2"x6" wether or not they are stick built simulation of a truss or not. More are using the Engineered Truss now that is manufactured with 2"x4" because of the Engineering behind it for the dead and live loads.

Looking at my Architectural Graphic Standards book Sixth Edition, with a Copyright of 1970, I guess it would be time to renew. ha. ha. Changing just takes me awhile guys, so bear with me. LOL.

Marcel
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[Kenton H. Shepard, CMI]

Site-built trusses, original home construction. Any sign of failure?

[jweinberg]

Originally Posted by kshepard

Site-built trusses, original home construction. Any sign of failure?

Nope....

[Dennis DiVito]

I am curious at this point as to why the nails are so long and why what appears to be plywood sheathing on spaced boards.??

Marcel


Plywood over skip sheathing.

The spaced planks (skip sheathing) originally was the roof decking under a metal roof. The later installation of plywood was for decking a shingle roof. I see it frequently in rural Virginia.

[Barry Adair]

Those long nails (look like 8d-10d) are probably not roofing nails and therefore may not be securing the shingles properly.

The only time I see the lath with ply overdecking is when a wood shingle system is torn off and they put on another system that requires solid decking such as comp, tile, metal...

[Marcel R. Cyr]

Thanks Dennis. That is what I thought, but was not sure.

Marcel