A Rundown House is a naturally occurring structure found in a Marsh biome. Its main purpose is spawning and housing Merms. In It has an appearance similar to that of a Pig House, but in a dilapidated state. It cannot be crafted by the player, making it non-renewable. Rundown Houses can hold up to four Merms and spawns a Merm every four days if any Merms are killed. During the day, only one Merm per Rundown House is normally outside. If that Merm gets into combat or when the house is struck with a Hammer, the rest of the Merms will come out and help it fight. Also, when Dusk comes, all Merms exit their house to wander around the vicinity.
In the Shipwrecked DLC, Rundown Houses are replaced by Merm Huts in Shipwrecked Worlds. Merm Huts have a more tropical and better maintained appearance compared to Rundown Houses. When destroyed, instead of Fish, they drop Tropical Fish. Otherwise, their behavior is identical.
- In the single player version, hitting a Rundown House with a Hammer once will make it look like a Pig House but behave normally.