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CMU lintels

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We prefer pre-cast lintels at our office, as do builders. They are quicker in lay-up by far then stopping to form a lintel. Also I have seen too many improperly constructed lintels to really like them. They have strength right away so the masons can keep laying up block. In FL, which I think is the biggest CMU block state, these are pretty much the standard, even on residential. We like them as engineers because they are easy- get an actual gravity, uplift, and lateral load and go to a table. Usually they are way over what we need. They get more stength because of lots of reasons, pre-cast concrete being stronger then grout filled block, and also they can fit more reinforcement in them as they cast some bars into the lintels. Sometimes they are prestressed too.
I don't know if they make them with split-faced finishes, but that would be one reason to use a regular lintel formed in the field. There may be other aeshtetic reasons like a curved lintel to not use pre-cast, or if they want an exposed block finish. I just finished some calcs on field-formed lintels for a project in the Virgin Islands- no precast supplier there....
Steel lintels- we had some problems in FL in this office because they produce them to a standard length then they are cut in the field. They do not come out in standard opening + bearing lengths. That creates a corrosion issue because they are hot dipped and you cut and expose the ends. I guess you have to make sure you have a good note covering this to be painted/coated in the field. They are great from a strength standpoint, go up fast, and finish nice with any type of block. I also believe they make special ones with built in brick angles...
My two pesetas,
Andrew Kester, PE
Longwood, FL