In New Zealand, it is generally possible to refelt a shed roof over existing felt, but there are several factors to consider before making that decision. Here are some key points:

  1. Condition of Existing Felt: The condition of the existing felt plays a crucial role. If the current felt is in good condition, with no significant damage, leaks, or deterioration, it may be suitable to refelt over it. However, if the existing felt is worn out, damaged, or has moisture-related issues, it is recommended to remove and replace it.
  1. Roof Structure: Assess the structural integrity of the shed roof. Adding an additional layer of felt can increase the weight on the roof structure. Ensure that the structure can support the additional load and that it is not compromised by any underlying issues.
  1. Compatibility of Roofing Materials: Confirm that the new felt is compatible with the existing roofing materials. Different types of felt may have varying installation requirements, and using incompatible materials can lead to poor adhesion or other issues.
  1. Building Codes and Regulations: Check local building codes and regulations. Some areas may have specific requirements regarding roofing installations, including restrictions on the number of layers allowed or specifications for roof underlayment.
  1. Cost Considerations: Refelting over existing felt can be a more cost-effective solution compared to a complete roof replacement. However, it is essential to weigh the cost savings against the potential risks and long-term performance.

Before deciding to refelt over existing felt, it is advisable to consult with a professional roofing contractor. They can assess the condition of the existing felt, evaluate the roof structure, and provide expert advice on the best course of action. They will consider factors such as safety, durability, and compliance with local regulations to help you make an informed decision about refelting your shed roof.