I had two roofers look at my house for some damage. There are about 10 shingles missing and another 10 tabs missing. The first roofer gave me the estimate and told me that he could directly add new shingles on the roof.

The second roofer did no give me an estimate at all, but he would repair whatever the insurance company pays. I thought that this way is more practical and I probably don't have to pay something that's not needed to be changed or repaired. I had to sign a contract with this roofer though that I would use him to get the job done. However, if the insurance company declines/disapprove the claim, this contract is automatically invalid.

I did sign the contract before the insurance adjuster came. The insurance company estimated the cost of the roof repair is much too low. The roofer said that he needed to take the layer underneath the shingles out in order to put the new one on. Thus, what the insurance estimates is not going to be enough to cover the repair cost.

Well, my question here is not about the insurance or the cost, but about ONE-layer shingle roof. I had these two roofers saying the different things. For repairs, is the layer underneath the shingles needed to be taken out/changed/replaced in order to repair. I actually HEARD from other people that only do double layer roof need to take the layer underneath the shingles off.