First of all if you have a mortgage they will make you take out for that amount , the rest it depends we're it's located , what's it made out of , how many stories , the replacement coast or actual cash value a lot goes into it .
I don't think that's true. The reason the lender requires you to get homeowners insurance is because if something happens they want to make sure they have a way of recouping the money they lent you. But if, for example the mortgage is for less than the value of the land, they may not even require any insurance. Obviously that's usually not the case, but the point is there is no set rule that you have to be covered to the full amount of the mortgage.
As far as the OP's question, if you're talking about a 'replacement cost' policy, you don't want to have a coverage limit higher than the replacement cost of the house (unless you need to raise one of the secondary coverages - which are usually calculated based off of the dwelling amount) because they won't pay you more than the replacement cost anyway. If you just went through the process of buying the house, what you can do is look at the report from the lender's appraiser. One of the methods they have for assessing whether the house is worth enough money to justify the mortgage is to assess the value of the land, cost of building the house etc. So you can use the building cost value listed there to determine your coverage amount.
