You don't need to have coal or log fires to burn a house down! Nearly 40 years ago, one of our neighbours decided to run a bath, whilst waiting for it to fill she turned on her gas oven, without lighting it, then lit a cigarette. Luckily she was blown straight out through the kitchen door into the garden, but he house was destroyed together with a lot of damage to the other semi detached house next door.
As you can imagine, the rebuilding cost was extensive, but was covered by her insurance!
Furthermore, if you still have a mortgage, your bank or building society will insist that rebuilding costs are fully covered.