Being biodegradable doesn't mean that it will degrade in any circumstances. Lumber in a house is usually protected from many biological degradation agents, even

Being biodegradable doesn't mean that it will degrade in any circumstances. Lumber in a house is usually protected from many biological degradation agents, even if it is not chemically treated. If you took that same wood and threw it in a pile exposed to rain and bugs, it would be gone in less than 100 years.