To obtain a permit for building an extension to your house, you will typically need to follow a specific process mandated by your local government or building authority. The specific requirements may vary depending on your location, so it's important to consult with your local building department or planning office for accurate information. However, here is a general step-by-step guide that can help you understand the process:

1. Research local regulations: Begin by familiarizing yourself with the local building codes and regulations that govern construction projects in your area. These regulations may include setback requirements, height restrictions, and specific design guidelines. You can usually find this information on your local government's website or by contacting the relevant department directly.

2. Engage an architect or designer: Depending on the complexity of your extension project, you may need to hire an architect or designer to create detailed plans and drawings. They will ensure that your extension meets all the necessary building codes and regulations. A professional designer can also help you with the overall design, functionality, and aesthetics of your extension.

3. Prepare detailed plans: Work with your architect or designer to create detailed plans and drawings of your proposed extension. These plans should include floor plans, elevations, construction details, and any other necessary information as required by your local building department. The plans should accurately represent the scope and scale of the project.

4. Submit your application: Once your plans are ready, you will need to complete an application for a building permit. This application typically includes details about the project, such as the proposed construction, materials to be used, and estimated costs. You may also need to include your property survey, site plan, and any other supporting documents required by your local building department.

5. Pay the fees: Along with your application, you will usually be required to pay a permit fee. The fee amount varies depending on the size and value of your project. The payment is typically made at the time of application submission.

6. Application review: After submitting your application, the building department will review your plans to ensure compliance with local regulations. They will assess the structural integrity, safety measures, and adherence to zoning laws. This review process can take several weeks, depending on the workload of the department.

7. Inspection and approval: Once your plans are approved, you will receive your building permit. However, before you start construction, you will need to schedule inspections at various stages of the project. These inspections ensure that the construction is progressing according to the approved plans and meeting all safety standards. Typical inspection points include foundation, framing, electrical, plumbing, and final inspection.

8. Complete the extension: With the necessary permits and inspections in place, you can proceed with the construction of your extension. It is crucial to adhere to the approved plans and any conditions outlined in your permit.

Remember, this is a general guide, and the specific requirements and process may vary depending on your location. Always consult with your local building department or planning office to ensure you have accurate information and to address any specific questions or concerns you may have.

References:

- United States: U.S. Small Business Administration - Building Permits: https://www.sba.gov/business-guide/launch-your-business/get-federal-and-state-tax-id-numbers/building-permits

- United Kingdom: Planning Portal - Do you need permission?: https://www.planningportal.co.uk/info/200130/common_projects/17/extensions