Are owners responsible for improvements to building by builder 4 years after building is occupied?

I cannot tell you what Washington law would be. In California the issue would depend on what is said in your CC&R's and in the bylaws of the Condo Association. I can only assume from your comment that the Condominium Complex was built in stages by the same developer, and each stage was governed by a different Condominium Association.

That raises issues as it regards the developer/builder's [if it is the case of a single entity] continuing right to make changes to the common area over the entire complex in order to revise and change each stage. In many projects the developer/builder retains the right to make architectural changes to harmonize the entire development. Those reserved rights are normally found in the recorded CC&R's.

This answer is under the Avvo system and is subject to its Terms of Use and is not to be considered as creating a lawyer/client relationship. I am only licensed in the State of California and this answer is based on California law.