This varies greatly from jurisdiction to jurisdiction. It also depends on what kind of work and how much.
In many locations, minor electrical work, in-kind plumbing replacement, interior construction that does not change the overall footprint or the number or types of bedrooms, bathrooms, etc, (such as the building of a closet in an existing room) need no permit. However, some locales may require new installations to come up to a newer code level than those that they replace. You really need to check with your local building department to see what is allowed without permit and when permits are required.
Failure to get a permit for work that requires one could result in a stop work order if the building authority learns of the project. It also could result in the property not having a valid certificate of occupancy, which could make selling the property difficult. It also might compromise your relationship with your lender. Finally, it may put your insurance coverage at risk if a claim is based on the work done in violation of permit regulation.
Often if work is not done based on a permit, it can later be corrected by filing a new application, submitting plans and paying a penalty in addition to the regular fees. But there is a risk that the plans will not meet the standards when the permit is eventually filed, and may fail, requiring a redo.
Your best bet is to check and see what is required before starting on a renovation. Then you can make an informed decision.
Are your 8-inch planks laid tightly together, or is there significant space in between? Old roofs that were originally topped with rigid shingles (wood or tile) were sometimes installed with spaced decking planks, and that kind of decking is not suitable for use under modern asphalt shingles, which are flexible.
However, if the planks are relatively tight together this is not a concern. The planks should be fine as long as they aren't damaged, and you'd only bother replacing damaged sections. Strip old shingles, add new underlayments, add new shingles.
Best Answer
These are metal shims - very very common.
You install ibeam and either right after install or after joists are installed you want to level everything out. You will need to shim at least one side.
This is really common. Dealing with ground settling, concrete shrinking and so on over a 60' or longer stretch you have two options:
Pay a ton of money to make sure all the planets align and your beam is perfectly level on concrete cut-outs. (and after all that money, it could still be off)
Put $2 worth of metal plates under to shim.
Those plates are not going anywhere - the weight of your house is on them. As an inspector it would not concern me in the least.
The only fear you should have is an overzealous inspector in your town - but this should be the same guy that signed off on the house in the first place. They could require the plates welded to the ibeam or to get a welded piece on that. This would require a temp post, jack it up and weld it on.
Also not sure what it looks like if you go further but I like my ibeam resting on a steel flange. I don't see that here and that bothers me more than anything. And looking at the picture further I would like to see the top of the beam - really doesn't make sense on what is going on there.
Notes based on 2nd picture: