warping roof steel to avoid adding crickets

[Nicole Brooks]

The GC on this single story tilt project has suggested warping all the steel on the low end of the building in order to save money by not having to have built up insulation crickets. Does this seem like a cost saving measure or just a huge headache to get the placement of the embed plates and joists just right? The structural engineer is very weary of this tactic and would prefer not to do it. He does not see this as a cost savings taking into account the extra roof drains that we need on either end of the building and any other erection problems we might face. Has anyone ever used this approach and what was the outcome?

 

[JPohling]

That sounds preposterous.

 

[tmurray]

I would rely on the advice of my engineer.

 

[TheCommish]

If the engineer designs and stamps it go for it.

many buildings are built with sloped roof trusses with built up insulation crickets to control the valley

 

[fatboy]

I would stick with YOUR engineer's opinion.

 

[Tim Mailloux]

The GC on this single story tilt project has suggested warping all the steel on the low end of the building in order to save money by not having to have built up insulation crickets. Does this seem like a cost saving measure or just a huge headache to get the placement of the embed plates and joists just right? The structural engineer is very weary of this tactic and would prefer not to do it. He does not see this as a cost savings taking into account the extra roof drains that we need on either end of the building and any other erection problems we might face. Has anyone ever used this approach and what was the outcome?

This is a very common practice and will certainly save money for the project.

 

[Paul Sweet]

Sloping the deck for sections of roof can be an economical method to reduce crickets. I'd be nervous about warping the roof structure; too many chances for errors.

 

[Tim Mailloux]

Sloping the deck for sections of roof can be an economical method to reduce crickets. I'd be nervous about warping the roof structure; too many chances for errors.

its done all the time....I would say that 90% of the roof structure & deck on any commercial flat roofs I design are sloped / warped. I try to only use tapered insulation for crickets at roof drains to divert water back to the drains.

 

[e hilton]

I would want a better definition of the original proposal. He said “warped”. To me that implies a non-linear piece of steel. Twisted. Curved. Different from sloped.

 

[Nicole Brooks]

its done all the time....I would say that 90% of the roof structure & deck on any commercial flat roofs I design are sloped / warped. I try to only use tapered insulation for crickets at roof drains to divert water back to the drains.

Yes, we are sloping all the joists 1/4" per foot to the low side, and then from the first column line in they are all at different slopes in order to create the valley for the roof drain. Each joist (6' apart) is 2.25" below the next, until the low point. Each of these joists will be sitting in a cast pocket in the tilt wall. To me, this just seems like a comedy of errors waiting to happen.

 

[Tim Mailloux]

Yes, we are sloping all the joists 1/4" per foot to the low side, and then from the first column line in they are all at different slopes in order to create the valley for the roof drain. Each joist (6' apart) is 2.25" below the next, until the low point. Each of these joists will be sitting in a cast pocket in the tilt wall. To me, this just seems like a comedy of errors waiting to happen.

again, this is a very common construction practice. It does require a little extra coordination and careful review of shop drawings, but it saves a considerable amount of money on the roofing, especially with a large roof where tapered can really add up.

 

[e hilton]

I don’t see the problem. Agree with Tim … just a matter of coordination and attention to details.

 

[Tim Mailloux]

Yes, we are sloping all the joists 1/4" per foot to the low side, and then from the first column line in they are all at different slopes in order to create the valley for the roof drain. Each joist (6' apart) is 2.25" below the next, until the low point. Each of these joists will be sitting in a cast pocket in the tilt wall. To me, this just seems like a comedy of errors waiting to happen.

I just noticed the 'tilt wall' piece of the puzzle. Is these are precast concrete walls panels fabricated in a shop / factory, coordination and quality control will not be an issue. If these wall panels are cast on site then I would probably stay away from this approach.

 

[Mark K]

What does the code say about it?

Unless something is compelled or prohibited the decision is left to the applicant and his or her consultants.

 

[Msradell]

I just noticed the 'tilt wall' piece of the puzzle. Is these are precast concrete walls panels fabricated in a shop / factory, coordination and quality control will not be an issue. If these wall panels are cast on site then I would probably stay away from this approach.

From my experience cast in the field panels are just as good as shop cast panels except in extreme circumstances.

 

[Nicole Brooks]

I just noticed the 'tilt wall' piece of the puzzle. Is these are precast concrete walls panels fabricated in a shop / factory, coordination and quality control will not be an issue. If these wall panels are cast on site then I would probably stay away from this approach.

THey are cast on-site.