I searched the forum for this but want to ask again specifically.

We are going to need to shim a pt site-built girder (3-ply 2×10) that will rest on masonry cmu concrete/rebar filled block.  We haven’t built the girder yet but pretty sure it will need shimmed around 1/4″.

I understand that shims should be sized so that the girder has full bearing over the shim as opposed to sticking some tiny shims in there, and I have also read that the shim should not be wedge shaped.

Question is – what exactly should we use to shim? When I search for shims, everything I’m seeing sold as a shim is small.  

I see a zillion pros/cons of wood vs steel. 

We’re in NE Tennessee, can see pretty heavy rainfall and be a very humid environment. Moderate to heavy termite presence.

I’m concerned as I know moisture and wood expansion/shrinking will likely be an issue to some degree.  Often the PT wood available around here seems relatively wet.

Crawlspace will be closed, and conditioned eventually with a dehumidifier.

County requires IRC 2018.

Cedar shingles seem like they’d be the easiest to source and cut to exact bearing size needed??

Thank you for any input.