Mono-pitched roof on garage letting daylight in along soffit / eave boards

First and foremost - please excuse my ignorance and improper use of terminology.

I have a free standing garage with a mono-pitched / shed style roof:



The garage is unfinished inside and I noticed that during the day there is daylight shining through all along the eave / soffit portion (I think that's what it's called. Basically where the high wall meets the top of the roof). I have also noticed a little bit of water damage on the high wall (which may be just do to the older roof) and a lot of / squirrel droppings.

From inside:



From outside:


-Are these gaps normal?

-Should they be sealed up?

-If so - how do I go about doing this? Expanding foam seems like it would make a mess as it expands to the outside.

-I do plan on finishing the inside of the garage at some point - so while I'm up there, would I need to install vents in the soffit?

 

While not great it is sort of common for there to be gaps underneath eaves and on soffits. I would look closely to see if water is actually getting in or it it's old damage. If things are getting wet then you need to find the source and fix it as it will only get worse.

If you don't like seeing the daylight coming through the soffit then you can caulk the cracks which will help keep insects out. But, don't simply rely on caulk if water is getting in as that may be better and more permanently fixed with flashing.

 

I figured that might be the case.

I recently got a moisture meter so I'll be keeping an eye on it after the rain. My current theory in terms of the source of the water damage is the lack of a drip edge.

I have no problem with the daylight so long as it's normal. If I plan on insulating and finishing the ceiling - is it worth installing vents in the soffit?

 

Not sure why you would insulate it unless you are planning on adding heat and air conditioning.

 

I would be hesitant to insulate the shed unless you have a really good reason. Insulation will trap any moisture and hasten rot so I'd make very certain you have any water problems taken care of. For a shed I wouldn't worry about roof venting. Plus, you don't have much roof pitch for ventilation to work well.