40FT 3 FT thick Load bearing beam supported by only one rafer?

[Susico]

Hello everyone.

So my main experience is in carpentry but have an avid interest in engineering so i tend to get a funny feeling when i see something that looks a bit strange.

A friend of mine recently had a load bearing wall removed which included a chimney breast. The roof pearl lines split at this area and on both ends they were propped bearing down on this wall. Also there were about 25 joists which were once supported by this wall.

Some builders came in an installed a big wooden beam to support all of the joists etc and one end of the beam was supported by a concrete wall. To my shock the other end of the beam traveled a distance of about 40 feet only to meet the roof at the other end where it had to be cut down to an angle corresponding with the roof. Since the beam could not reach that external wall because the roof was in the way they bolted the beam to a single 4 x 2 rafter. I know from my experience as a roofer that these rafters are held in place with 2 four inch nails into the wall plate.

I have included a picture to supplement my explanation of the situation. Basically all of the weight of this beam and all that it is supporting including the roof via the pearl lines is bearing down on this one rafter.

Shouldnt a beam like this be supported by either two load bearing walls on either end or at least some kind of pillar on either side?

 

[Susico]

In the second picture the "pearl line support" text is too far to the right for some reason, it should be over that support that comes down at an angle to the left of the beam.

 

[MotorCity]

What's a pearl line?

 

[Susico]

Oh sorry its been about 15 years since I was roofing so my terminology/spelling might be a bit off. Its spelled Purlin and it is a beam which supports the weight of the roof at the center of the rafters.

 

[BridgeSmith]

Its spelled Purlin and it is a beam which supports the weight of the roof at the center of the rafters.

What you describe sounds more like a ridge beam.

Without seeing the rest of the roof system, I can't tell what the LVL is supporting, and whether there is anything missing from the support structure.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Susico]

Not sure how to quote your post BridgeSmith but to answer your question the Purlin im describing is labeled as the "under purlin" in this diagram and the "purlin support" is labeled as the "prop" beneath the under purlin in this diagram.

The following diagram also gives a pretty good idea of the structure of this roof.

 

[RPGs]

Suscio, it's difficult to tell what's going on. This would definitely require a site visit to really understand what the beam is supporting currently vs. what the bearing wall used to support.

It appears the beam is only supporting a portion of the attic/ceiling joists, some of which are headered off, which are quite light on their own, but I would be surprised if this configuration will calc out to support code-required loading, especially if it's single-shear bolted at one end to a 2x4 rafter as you stated.

I'm not sure what your role is in the project, but I recommend contacting a licensed PE to review the construction of the beam and draft you a report if you have concerns.

 

[BridgeSmith]

Ah, now I understand the purlin. I still don't understand what the LVL beam is doing, unless what you have shown as the "wind brace" is attached to the LVL and is thereby supporting the ridge.

Rod Smith, P.E., The artist formerly known as HotRod10