Exterior use of microlams

[mattradk]

I was asked to look at a set of plans for a deck that were prepared by a large local lumber and building supply company. It's a simple rectangular deck off the back of a house.

The joists are treated 2x8's, all supported by a single beam that's spec'd as 3-2x10LM. I haven't seen "LM" on a lumber designation before so I called and asked what it meant. I was told it meant "microlam."

This is the first time I've heard of an exterior use for a glued engineered member (microlam, LVL, etc.). Is this permissible/advisable?

Thanks!

 

[Phil1934]

Weyerhauser's Parallam is pressure treated as is Pacific Woodtech's LVL