system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: When a house gets completely burned down, how can experts figure out where the fire originated?
gpt
I am a licensed General Contractor, noticed the responses didn't give any insight as to what fire inspectors look for so i thought i would try to. To start, one must understand how houses are built to a small degree. By today's standards, all materials are built with materials that have a fire rating. Drywall for example is comprised of approximately 1/5th water, when it burns the water converts to steam slowing the fires ability to spread. This also means that each material reacts differently to heat and flame over time. Fire inspectors have the knowledge of what materials look like after being exposed to different temperatures at different lengths of time. Similar to how an ice cube will melt faster on a hot day than a cold one, fiberglass insulation, OSB, and framing studs burn at different rates. When homes are being built they add "fire barriers" to slow the burn. Fire calk and fire resistant insulation between levels of a home is a good example of this. These slow down the fire, so the materials toward the origin of the fire will have been exposed to more heat and flame for a longer period of time so the damage will be more severe. another thing they look for are common causes each with their own signs. For example an electrical fire will show signs of arcing or "black marks" on the walls etc. Hope this helped a little bit.