Instead of "shack-like," you could use:
* Dilapidated: Describing something in a state of disrepair.
* Run-down: Similar to dilapidated, emphasizing neglect and poor condition.
* ramshackle: Suggests a structure that is likely to fall apart.
* Crude: Implies something hastily built and lacking in refinement.
* Hasty: Similar to crude, suggesting something built quickly without much care.
* Improvised: Describes something made with whatever materials were available.
The best choice depends on the specific context and the nuance you want to convey.