Framing a New Roof on Top of an Existing PEMB Roof 5

[structuralengr89]

Would anyone ever consider framing a new roof on top of an existing PEMB? I have someone who has adjacent pre-engineered metal buildings and wants to frame a new roof between them to get rid of the valley. Reasons to not do it:
1. Expansion/Contraction. Tying 2 buildings together with framing between the valley would change how the buildings move with temperature.
2. Collateral Loads. I see many PEMB's in my state, where the PEMB engineers are indicating 1 PSF for collateral! Not enough capacity.
3. Liability. You touch it, you own it.


If I had good documentation that said I had maybe 10 psf collateral and the buildings were small...I might consider framing with some CFS framing above.

 

[JAE]

Your reason 1: You could overbuilt two roofs with an expansion joint between them - still gets rid of the valley but allows differential movement.
PEMB's move a lot so a large EJ would be required for both directions - hard to create and maintain for a roof.

Your reasons 2 and 3: Yessir

 

[dik]

PEMBs are so tightly designed that they may not be able to accommodate the added loading.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[bones206]

I like to tell clients: pre-engineered buildings are not meant to be post-engineered.

 

[KootK]

How wide is the PEMB and how tall is the step between buildings?

Also, what is the reason to do this? What is the client trying to achieve? Better drainage? Less snow buildup?

I like to tell clients: pre-engineered buildings are not meant to be post-engineered.

That's gold; I'm using it.

 

[TLHS]

Wait, is this two existing buildings, or is this one existing building that a new one is getting installed directly beside?

How close are they?

 

[Brad805]

Great line Bones.

 

[bones206]

It’s my weak attempt at expectation management. People usually don’t want to hear it though.