Allot of sheds are plastic, vinyl, wood, or metal. The cheaper the shed the more flammable. Then think about what's in your shed. Usually people store cardboard boxes, plastic bags, plastic toys, swim toys, chemicals of sorts. The fact of is most outdoor sheds are just waiting to go up in flames. Don't let that happen to you or your backyard will look like this... Luckily the fire didn't spread to the house next door or the tenants.