Some Odd Shapes after Lighting Building

[emrebaris]

Hello folks. I am a new unreal engine user and I have a problem with lighting building of my house model. Before building, the house is not perfect but better than its built condition. My before and after photos are as follows.
Why is it so, and how can I get a nice lighting build?

Thanks in advance.

Before:

After:

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[Tim_Hobson]

Looks like you need to setup a proper lightmap for your mesh. Take a look in the documentation for lightmapping to see how this should be done.