Will your house fall down if there's too much weight on the 2nd floor if its made out of wood?

Short Answer... YES

Reality... it would take a very large amount of weight to bring down a wood house.

Take for instance the usual design load found in most homes today. The home must be designed to carry a 30 PSF live load and a dead load of 20 PSF (PSF = Pounds per Square Foot), for a total design load of 50 PSF.

A 50 psf load in a house with a floor space of 1000 sf would be a load of 50,000 lbs or about 25 tons to reach the design maximum.

With that said, the actual load required to create failure would be much greater due to design increases required for safety factors. At which time bowing of the floor/ceiling assembly would be noticed before catastrophic failure occurred and the floor collapsed.

If there are damaged structural members or point loading occurs, failure could be expected sooner.

This is a simple description of the concepts

Terry