Ok to use horizontal vent like this?

[Greg5OH]

I want to run a 40k BTU 10ft radiant tube heater in my attached garage. Vent would be horizontal going through a combustible wall, outside being T11 shiplap.
This is the vent I want to use, also called out by the tube heater mfg.

I can't see in the vent instructions how much room I need below the soffit? Its a normal house soffit, about 12" projection. I was going to go 12" under it...
anything wrong with that?

 

[The Cobbler]

is the soffit vented? I'm thinking the 4' rule would apply

 

[stokefire7]

Doesn't really say, does it.

 

[stokefire7]

NFPA #54 is what you're looking for.

 

[stokefire7]

One issue I see is that flue gasses are corrosive, you may have discoloration of your T-111.
Looks like your vent terminal is directional (which is a plus) ?