Yes, it will have to re-calculate the lighting. If you are have a static scene, build lights and then make modifications it will invalidate your previous light build and re-calculate lighting from your directional light, spotlights or pointlights when you built the lights again. However, if you are not creating a project where performance is the main priority you can try a dynamic lighting scene could work better for you, this removes the requirement for light maps and allows all lighting to be ran at real-time via the GPU.
For more information check out this Lighting Troubleshooting Guide:
https://wiki.unrealengine.com/LightingTroubleshootingGuide