This was an unusual framing configuration for me. Obviously wrong with the disconnected metal straps, but I was hoping one of our engineers could enlighten me with this configuration. The unattached metal straps are fairly thin and offer no compressive strength to the roof structure. The roof is completely supported by the webbing with the metal straps only offering tensile strength to the roofing—and I’m unclear on it’s function.
Thanks in Advance!
That was my first thought, but it’s on a poured foundation. It was built in 1957. Roof framing and webbing is bolted together.
Are those square headed nuts/bolts? If so, that’s an indication of age for sure. Whatever it is looks pretty old. Looks like a metal workers house. Guys that work with metal will do EVERYTHING with it. It’s like a pride thing… they refuse to buy wood.
Actually, it was a whole neighborhood of similar homes. I’m guessing 1957 Prefab homes, but someone may set me straight on this one. It’s just not something I’ve run into before.
Likely that, or something similar. I’m still at a loss on the purpose of the upright straps. They were thin enough that you could fold them over double with your hands. The disconnected ones caused no soft spots when walking on the roof. I’ll recommend reconnecting them, but I’d like to know their purpose in the structure for my own education.
Right, so they must hold something up. What’s the floorplan directly below? Outside photo? Detail photo of the pin attachment (e.g. why did it come out?).
Is there a load bearing wall under this truss like roof system? Can you draw a sketch showing how all the parts fit together?
Scott may be on to this; A king post in this style truss is under extraction, not compression pressure. That would explain the thin metal. I see diagonal struts, queen posts, farther down the rafter. Queens are lumber because thay are under compression.
The wall on the right side is a load bearing wall running the length of the home offset about 3 feet from the center of the trusses. The area under the unattached straps is shown here (about 4 feet past the attic access) with no sagging in the ceiling. Thanks!
With a truss roof, how can you call the wall below the trusses a bearing wall?
Looking at the photos, I’ve been cogitating and I have come up with something that would account for the elements shown. Note; I’m not going to attempt to figure out the “why”, just the “how”. The equi-distant triangle has been used for clarity - the actual structure is lower and wider:
The rough diagram above shows not one but two trusses - B, D, E & E, F, C
Each triangle has one side extended to double it’s length (1 => 2 and 4 => 3) such that the extended legs meet at point A
Downward force applied at point A would therefore be spread across points B, C and E evenly
Lateral force on side 2 or 3 would be countered by the support at both ends of DA or AF
Upward force (wind lift) or lateral force on sides 1 or 4 would cause sides 2 and 3 to separate at point A, forcing them apart.
This would account for the requirement for the vertical metal straps running from A to E - they don’t need to handle compression as that is already taken care of.
Assuming that beam B, E, C is one continuous piece, then most of the load would be carried at points B & C, but an additional load bearing wall at or near point E would certainly help.
The question remains as to why the straps were disconnected and left that way. My guess would be that someone removed them to work or get around them, and simply left them like that as they “didn’t seem to be needed”.
As for the “why”, this is pure conjecture:
Q I’ll bet you can’t frame a roof without a king post!
A Hold my beer!
This is all just a theory - thoughts welcome!
Very nicely done and explained, Dave! Thank You.