If you're building a chicken run, one of the decisions you'll need to make is whether to use roofing felt under the shingles.
Roofing felt, also called tar paper, is a water-resistant material that is commonly installed under asphalt shingles or other roofing materials.
But is it necessary or beneficial for a chicken run roof? Here is a comprehensive look at the pros and cons of using roofing felt under shingles on a chicken run to help you decide.
What is Roofing Felt?
Roofing felt is a paper or fiberglass mat that is coated with asphalt. The asphalt coating makes it water resistant to serve as a protective barrier between the roof deck and the shingles.
There are different grades of roofing felt indicating the level of durability and weather resistance. Common grades used in residential roofing include:
- #15 felt - The lightest grade for use in drier climates
- #30 felt - The most commonly used grade for typical residential roofs
- #90 felt - A heavier grade for use in wetter climates
Roofing felt is commonly sold in rolls 3 feet wide and 36 feet long. It is relatively inexpensive roofing material, costing $15-$30 per roll.
Benefits of Using Roofing Felt Under Shingles
Here are some of the benefits that roofing felt provides when installed under shingles:
Acts as a Leak Barrier
The primary purpose of roofing felt is to act as a leak barrier between the roof deck and the shingles.
If water seeps through the shingles, the felt creates a secondary layer of protection to prevent leaks.
This helps buy time to repair or replace any damaged shingles before water damages the roof deck.
Prevents Wind Damage
In high winds, the felt helps grip the shingles to the roof deck, preventing them from lifting up.
This provides extra resistance against wind damage.
Evens Out Minor Deck Irregularities
Small imperfections or warped areas in the roof deck can be covered by the felt to create an even surface for installing shingles.
This helps the shingles lay flatter and seal better.
Provides a Thermal Layer
The asphalt coating makes roofing felt slightly thermally insulating. This can help moderate temperature swings in the chicken coop, keeping it cooler in the summer and warmer in winter.
Extends Shingle Life
By protecting shingles from wind, weather, and deck irregularities, the felt helps extend the lifespan of the shingles.
This added durability can be important for chicken run roofs that withstand a lot of use.
Facilitates Re-roofing
When it's eventually time to re-roof, having roofing felt under the old shingles allows you to install the new shingles over the top. This avoids needing to tear off and replace the roofing felt, saving time and cost.
Drawbacks of Using Roofing Felt
There are also a few potential drawbacks to consider about using roofing felt under shingles:
Adds Material Cost
Obviously, purchasing and installing the roofing felt adds cost to the project budget. For a small chicken run roof, this may amount to $50-$150 in materials.
Trickier to Install
Proper installation of roofing felt takes some roofing knowledge and skill. The felt needs to be overlapped correctly and sealed down well, especially around valleys and projections.
Improper installation can actually cause leaks or other problems.
Vulnerable to Sun Damage
Unless protected by shingles, roofing felt degrades relatively quickly in sunlight. Any felt that remains uncovered for long can become brittle and ineffective.
Not Necessary for Shed-Type Roofs
On simpler shed-style roofs with minimal pitch, roofing felt provides less benefit. The lack of valleys and projections reduces leak risks.
Felt may be unnecessary if shingles will be installed immediately.
May Attract Vermin
Rodents or insects can potentially chew through roofing felt to access the warm, dry area under the roof.
However, this is not common.
Do You Need Roofing Felt for a Chicken Run?
Whether you need roofing felt under the shingles depends on a few factors:
Roof Pitch - The steeper the roof pitch, the more benefit roofing felt provides. On very shallow pitches, it may not be necessary.
Rain and Snow Levels - In wet climates with heavy precipitation, roofing felt helps protect against leaks. In drier areas, it provides less advantage.
Roof Complexity - For simple roofs with few projections and valleys, felt is less critical than on complex roofs.
Cost Considerations - If budget is tight, skipping the roofing felt could save on materials.
DIY or Professional Install - Skill at properly installing roofing felt impacts whether problems could occur without it.
Here are some recommendations on when to use roofing felt under shingles on a chicken coop:
Recommended
- Steeply pitched roofs greater than 4/12 pitch
- Climates with heavy rain or snowfall
- Roofs with multiple valleys and projections
- When hiring a professional roofer to install the shingles
Optional
- Light precipitation climates
- Simple shed-style roofs with pitch 2/12 to 4/12
- When on a tight budget
Not Necessary
- Very shallow pitched lean-to roofs less than 2/12
So in summary, for most typical backyard chicken run roofs, roofing felt is a recommended best practice.
The moderate cost is justified by the added leak protection and durability. It's an easy way to add an extra layer of insurance against weather damage.
However, for very basic roofs in drier climates, the cost of roofing felt may not be warranted. Evaluate your specific situation to decide if you should use it under the shingles or not.
Choosing the Right Roofing Felt
If you decide roofing felt makes sense for your chicken run roof, make sure to choose an appropriate product:
Use asphalt-coated felt - This is more durable than plain felt or synthetics.
Choose #15 or #30 weight felt - Heavier #90 is overkill for a chicken coop.
Select an ASTM D226 Type I ("Standard") grade - This is the common grade for residential use.
Look for fiberglass reinforced felt - This lasts longer than organic felt.
Get wide rolls - 36" rolls cover roof area faster with fewer seams.
Choose a synthetic underlayment - If you want added durability and tear resistance.
Make sure any product you choose is clearly labeled as meeting ASTM D226 standards for asphalt-saturated roofing felt.
Proper Installation of Roofing Felt
To gain the full benefit of using roofing felt, it's critical that it's installed correctly:
Install over entire roof deck - Don't leave any areas uncovered.
Run felt horizontally - Start at the bottom edge, overlapping vertical seams.
Overlap seams by 4-6 inches - And seal with roofing cement.
Lay felt wrinkle-free - Smooth out any bumps, wrinkles or folds.
Use metal drip edge - Install drip edge then place felt over it.
Seal around roof edges - Apply roofing cement along eaves, rakes, and projections.
Cut and seal around penetrations - Use roofing cement to seal felt around vents, ducts, etc.
Apply shingles promptly - Don't leave felt exposed to the weather any longer than necessary.
If you don't have roofing experience, it's a good idea to have a roofing contractor install the felt to ensure proper overlaps, sealing, and integration with flashings.
Alternatives to Asphalt Roofing Felt
There are a few alternatives that provide similar leak protection as asphalt roofing felt:
Synthetic roof underlayment - Made from woven or spun polymers, these are more tear resistant.
EPDM rubber membrane - Rubber sheets that adhere to the roof and serve as durable underlayment.
Ice & water barrier - Special membranes used at roof edges, valleys and projections.
However, these alternatives are generally more expensive than asphalt roofing felt. For a basic chicken run roof, conventional felt usually provides sufficient durability at the best value.
Related Considerations for Chicken Run Roofs
When installing roofing felt and shingles on a chicken coop, there are several other roofing factors to consider that impact performance and durability:
Roof Framing and Rafters
The roof rafters provide the essential framework that the roof sheathing and shingles are attached to. Use the appropriate rafter design and spacing to support the load.
Roof Slope and Drainage
Adequate roof slope and drainage prevents water from pooling on the roof. This is especially important with roofing felt to avoid leaks.
Ventilation
Proper ventilation removes moisture and heat from the coop interior and attic space. This helps maintain roof integrity.
Roofing Material Options
Beyond shingles, metal and plastic roofing like corrugated plastic are options to consider for durability and weather resistance.
Roof Access Points
Accessible roof openings make inspections, cleaning, and repairs easier without damaging roofing.
Supplemental Waterproofing
Extra water protection like ice & water barrier helps high risk areas like eaves.
Electrical Considerations
If adding lighting, electrical boxes and wiring need to be properly integrated.
Maintaining Appearances
Painting or staining not only enhances appearance but also protects the roof.
Thinking through these additional factors helps build a comprehensive roofing strategy for maximum chicken run protection, functionality and longevity.
Roofing felt serves as just one key component within the full roof assembly.
Final Recommendation
Installing roofing felt under the shingles is recommended for most chicken run roofs beyond the most basic designs.
For relatively little cost, it reliably protects against wind damage, leaks, and sheathing deterioration.
This preserves the structure of the chicken run and saves on repairs or replacement costs over the long term.
Be sure to choose an appropriate ASTM D226 certified asphalt felt product. And take steps to ensure it is installed fully and sealed properly at seams and edges.
Correct installation is just as important as using the underlayment.
With roofing felt installed under the shingles, you can have confidence that your chicken run's roof will effectively stand up to rain, snow, wind, and sun.
Your chickens will stay dry and comfortable in their coop, season after season.