Shed roofing felt is a popular and reliable material for protecting garden sheds and outdoor structures from the elements. While shed felt is highly effective on its own, many homeowners and builders wonder whether adding an underlay is necessary. The short answer is: underlay isn’t always essential, but it can significantly improve the durability and performance of your shed roof. Let’s explore why underlay might be worth considering and when it’s most beneficial.
What is Roofing Underlay?
Roofing underlay is a protective layer installed beneath the shed felt. Typically made from waterproof or breathable materials, it acts as an additional barrier to prevent moisture, condensation, and wind from penetrating the roof structure.
In roofing systems for buildings with a pitch of less than 20 degrees, underlay is often used to enhance waterproofing. This same principle can be applied to sheds, especially in areas with harsh weather conditions or if the roof structure is particularly vulnerable to moisture damage.
Benefits of Using Underlay with Shed Felt
Adding an underlay beneath your shed roofing felt provides several advantages:
1. Enhanced Waterproofing
Underlay creates an extra layer of protection against water ingress, which is particularly useful in rainy or snowy climates. If the felt is damaged or worn over time, the underlay acts as a backup to prevent leaks.
2. Reduced Condensation
Breathable underlay helps to regulate moisture by allowing condensation inside the shed to escape while keeping external water out. This prevents mold growth and protects stored items.
3. Improved Insulation
An underlay layer can add a level of insulation, helping to maintain a more stable temperature inside the shed. This can be especially beneficial if you’re using the shed as a workshop or for storing temperature-sensitive items.
4. Increased Durability
By supporting the roofing felt, underlay reduces the wear and tear caused by friction, wind, or other environmental factors. This extends the lifespan of your shed roof.
5. Cost-Effective Maintenance
Although underlay is an additional upfront cost, it reduces the likelihood of needing expensive repairs or replacements down the line.
When is Underlay Most Beneficial?
While underlay is not mandatory for all shed roofs, there are certain scenarios where its use is highly recommended:
- Low-Pitched Roofs: Roofs with a pitch of less than 20 degrees are more prone to water pooling, making underlay an excellent safeguard.
- Harsh Weather Areas: In regions with heavy rainfall, strong winds, or snow, underlay provides added protection.
- High-Value Contents: If you’re storing valuable tools, equipment, or furniture in your shed, underlay can ensure extra peace of mind.
- Old or Damaged Roofs: For older sheds or those with compromised roof structures, underlay can provide reinforcement beneath the felt.
How to Install Shed Felt with Underlay
If you decide to use underlay, here’s a basic guide for installation:
- Prepare the Roof:
Ensure the roof deck is clean, dry, and free from debris or damage. Repair any loose or damaged boards. - Install the Underlay:
- Roll out the underlay from the bottom edge of the roof, working upwards.
- Secure it in place using nails, staples, or adhesive.
- Overlap each strip by at least 100mm to ensure a watertight seal.
- Apply the Shed Felt:
- Roll out the shed felt over the underlay.
- Nail it in place along the edges and overlaps, spacing the nails every 100-150mm.
- Trim any excess material for a clean finish.
- Inspect the Roof:
Once the felt is in place, check for any loose edges or gaps and secure them as needed.
Do All Shed Roofs Need Underlay?
In most cases, shed felt alone is sufficient to protect your shed roof, particularly for smaller structures with minimal exposure to harsh weather. However, if you want to maximize the lifespan of your shed roof and protect against potential issues like leaks or condensation, adding underlay is a wise choice.
Conclusion: Is Underlay Worth It?
While shed roofing felt is a robust and reliable material on its own, using underlay can provide an extra layer of protection and durability. If you’re building or repairing a shed in a challenging climate, have a low-pitched roof, or want to enhance the longevity of your shed, underlay is a valuable investment.
For high-quality shed felt and roofing underlay, browse our range at GetYourselfFelt.co.uk. We stock everything you need to create a durable, weatherproof roof for your shed or outdoor structure. Shop now and give your shed the protection it deserves!
