PWT treated laminated veneer lumber is the first LVL that can be used outside. We’ve used LVL for at least 20 years but never had a product for the exterior.
The treated wood we get in the Pacific Northwest is not fun to work with—it’s inconsistent and extremely heavy. It’s treated by forcing water into it. When we receive it, the lumber is squirrely and inconsistent. Its weight also limits how much you can carry and wears you out. We go with concrete over wood decks whenever we can because of this.
PWT Treated LVL is more money, but it’s consistent and you don’t have to crown anything. You save quite a bit on labor, and the treatment is different than our treated lumber. It’s also stronger and stiffer, so with your deck design, you could lessen the number of columns and hardware used, saving money. With regular treated wood, you still have to cut, so we order up to 20% more wood, knowing we need to cull everything. It’s expensive.
The only difference is that it’s recommended to use a sealer if Treated LVL will be exposed to the elements, so it doesn’t take on an overly weathered appearance. It takes no time at all. Regular treated lumber requires you treat each cut so it doesn’t rot—this is more of an appearance thing.
Plus, you need to tape the top of the joists, but many do that with regular lumber.