Window Inspections - Double Buck Conditions

[SoFloJoe]

Hi All,

I do special inspections from time to time for window contractors in South Florida. This project the city inspector specifically asked for an engineer to provide a letter approving the double buck condition, the NOA does not have a double buck configuration.

Essentially what is going on is there are 2x4s on top of 2x4s and then they are using 1bys (0.75") or shims to fill the gap. Is there a specific code that covers this? I do not see anything about it in the Florida Building Code or NDS, maybe looking in the wrong place.

My thought though is as long as the wood members are properly secured than it should be ok, I would include a simple detail specifying the screw requirements at each level. And to have a minimum of 3" wood screws going through at 9" o/c staggered at each new level and the last one connecting to the CMU to have concrete screws with a 1.5" min embedment or per NOA which is more stringent.

Has anyone else run into this?

Thanks in Advance!

 

[Ron]

Joe....how did the rough opening get so far off? Did they order the wrong windows?

FBC doesn't limit the bucks other than to require PT. Though it's not a good condition and particularly if this project is in the HVHZ, I agree...just make sure the attachment is good. I would fasten each layer separately to reduce fastener bending. I would also require more stringent waterproofing as there might be enough flex in the system to break the waterproofing. How do they intend to hide the bucks?

Also, deviating from the NOA or Florida Product Approval will increase your liability.

 

[SoFloJoe]

Thanks Ron

how did the rough opening get so far off?

Well apparently the windows that were there before were framed out this way. They ordered new windows based on the existing window sizes and when they opened it up found this configuration. The city inspector requested that an Engineer approve the double buck condition.

I would fasten each layer separately to reduce fastener bending. I would also require more stringent waterproofing as there might be enough flex in the system to break the waterproofing. How do they intend to hide the bucks?

Thanks for the suggestion! Hardy board/stucco on exterior and drywall on interior. I do not usually get into spec'ing waterproofing, do you think a simple note of "waterproofing with high resistance to flexure required" is adequate?

Thanks again!

 

[Ron]

Joe...if you don't provide any waterproofing info usually, your note is good. FYI....I would specify Prosoco R-Guard FastFlash for an application like this. I'm doing a window replacement project right now with 680 windows in masonry openings. Fortunately keeping the bucks as thin as possible.

 

[r13]

Unless you are quite familiar with waterproofing materials and technics, I'll stay away from specifying a particular product. As Ron said, your note is good enough.