This depends on the type of project and which section of the Planning Laws that it falls under.
This is usually either Permitted Development, where planning permission is not specifically required. Or Planning Approval where planning permission needs to be sought before any construction work can start.
Permitted Development often requires confirmation by the Local Authority but almost always requires Building Regulation approval.
Planning Permission requires an application to Local Authority which usually takes 8 – 10 weeks after submission for a decision (be it an approval or refusal). Again, successful planning application requires building regulation approval.