Yes, roofing felt can get rained on, but it’s not ideal. Traditional felt paper (15# or 30#) will absorb water, get heavy, wrinkle, and lose strength when wet. After 20+ years of roofing, I can tell you that wet felt is one of the most common headaches on job sites—and honestly, it’s why I switched to synthetic underlayment years ago.
But if you’re using felt and it gets wet, don’t panic. It happens constantly. Here’s what you actually need to know.
What Happens When Roofing Felt Gets Wet
Roofing felt is made from organic or fiberglass mat saturated with asphalt. When it gets rained on:
Immediate effects:
- Absorbs water like a sponge (40-70% by weight)
- Becomes heavy and difficult to work with
- Gets slippery—seriously dangerous to walk on
- Can tear easily when saturated
After a few hours:
- Starts to wrinkle and buckle as it expands
- May develop “fish mouths” (lifted edges at seams)
- Can sag between rafters if deck spacing is wide
If it stays wet for days:
- Loses significant tear strength (50-70% reduction)
- Develops permanent wrinkles that won’t flatten
- May start deteriorating and breaking down
- Can cause the roof deck underneath to stay damp
Here’s the truth: One rain shower won’t ruin felt paper if you handle it right. Multiple wettings or extended exposure? That’s when you’ve got real problems.
How Long Can Felt Paper Be Exposed?
Unlike synthetic underlayment, felt paper has very limited exposure tolerance:
Maximum exposure times:
- 15-pound felt: 2-7 days maximum (some products advertise 30 days, but I don’t trust it)
- 30-pound felt: 7-14 days maximum in dry conditions
- When wet: All bets are off—get it covered ASAP
UV damage is brutal on felt. The sun dries it out, makes it brittle, and causes cracking. I’ve seen felt paper that sat exposed for 3 weeks basically disintegrate when you try to work over it.
Compare that to synthetic: 90-180 days exposure. That’s why the roofing industry has largely moved away from felt.
Why Roofing Felt Gets Wet (Common Causes)
In my experience, felt gets wet for a few predictable reasons:
During installation:
- Didn’t check weather forecast (guilty of this early in my career)
- Job took longer than expected, ran into next day when rain hit
- Pop-up storms that weren’t forecasted
- Didn’t tarp overnight and dew soaked it
Poor installation:
- Inadequate overlap (should be 2″ side, 6″ end laps minimum)
- Not enough fasteners—felt lifts and water gets under it
- Wrinkled installation that creates pockets for water
Storage issues:
- Felt rolls stored outside and got wet before installation
- Once felt absorbs moisture in storage, it’s compromised
Extended exposure:
- Job delays (permits, material shortages, weather)
- Left uncovered between phases
- Budget issues stopping work mid-project
What To Do When Felt Gets Wet
Alright, it rained on your felt. Here’s the real-world process I follow:
Let It Dry Completely
Don’t do anything until it’s dry. This is critical.
- Sunny weather: 6-12 hours drying time
- Cloudy/humid: 24-48 hours
- Cold weather: 48+ hours
Never install shingles over wet felt. I don’t care how far behind schedule you are. Wet felt needs to dry or you’re trapping moisture against your roof deck. That causes rot, mold, and shingle adhesion problems.
Speed up drying:
- Remove any standing water with a soft broom or squeegee
- Don’t walk on it more than necessary when wet—you’ll tear it
- If you’ve got big wrinkles with water trapped, you might need to cut small relief slits to let water out (do this carefully)
Inspect for Damage
Once it’s dry, walk the roof and check:
Replace felt if you see:
- Large tears (bigger than your hand)
- Extensive wrinkling that didn’t flatten after drying
- Felt that’s become brittle or is cracking
- Areas where felt has separated from the deck
- Signs of deterioration (material breaking down)
You can continue if:
- Minor wrinkles that flattened during drying
- Small tears (less than 6 inches)
- Felt still has structural integrity
- It only got wet once and dried properly
Small Repairs
For minor damage:
- Small tears: Patch with a piece of felt, 12 inches larger than the tear, nailed around the edges
- Lifted seams: Re-fasten and ensure proper overlap
- Wrinkled sections: If they’re small and flattened after drying, you can continue—just make sure shingles lay flat over them
When to Replace Sections
Replace the felt if:
- It got wet multiple times
- It’s been exposed over 2 weeks
- Wrinkles won’t flatten
- Material feels weak or tears easily
- You can see daylight through it
Replacement process is straightforward:
- Remove damaged felt and fasteners
- Check roof deck—if it’s wet, let it dry completely
- Install new felt with proper overlap (2″ sides, 6″ ends)
- Nail every 12-18 inches
- Cover with shingles as soon as possible
Why Felt Paper Has Problems (The Honest Truth)
I started my roofing career using felt paper exclusively. It was the industry standard. But felt has real limitations:
Problems with traditional felt:
- Absorbs water readily
- Tears when wet
- Heavy to carry (especially when wet)
- Short UV exposure tolerance
- Wrinkles and buckles
- Deteriorates in heat
- Limited lifespan even when installed correctly
I switched to synthetic underlayment around 2010 and haven’t looked back. Jobs go faster, fewer callbacks, better protection. More on that below.
Better Alternatives to Roofing Felt
If you’re planning a roof or replacing wet felt, consider these options:
Synthetic Underlayment (My Top Recommendation)
Products I use: GAF Deck-Armor, Owens Corning ProArmor, CertainTeed RoofRunner
Why it’s better:
- Doesn’t absorb water (less than 1%)
- 4-6 times stronger than felt
- Lighter weight (easier to handle)
- 90-180 day UV exposure rating
- Doesn’t wrinkle or buckle when wet
- Dries in 4-6 hours vs. 24+ for felt
Cost: $70-150 per square vs. $15-40 for felt
Is it worth it? Absolutely. The labor savings alone justify the cost. Plus, if rain delays your job, you’re not replacing water-damaged felt.
Self-Adhering Underlayment
Products: Grace Ice & Water Shield, GAF WeatherWatch, Owens Corning WeatherLock
Best for:
- Valleys (100% waterproof protection)
- Eaves in cold climates (ice dam prevention)
- Low-slope areas
- Around penetrations
Cost: $120-250 per square
Note: This is overkill for an entire roof, but essential for vulnerable areas. I use it on every roof for valleys and first 3-6 feet at eaves in cold climates.
Rubberized Asphalt Underlayment
What it is: Self-adhering modified bitumen material
When to use:
- Low-slope roofs
- Areas with severe weather
- When you need guaranteed waterproofing
Downside: Expensive and harder to install than synthetic
Breathable Membrane
Products: Certain synthetic underlayments designed for vapor permeability
When to use:
- Metal roofing applications
- Situations where moisture needs to escape from below
- Specific climate conditions requiring vapor management
Note: Most residential applications don’t need this—standard synthetic works fine.
My Professional Recommendations (After 20+ Years)
Here’s what I actually do on roofing jobs:
For New Roofs or Re-roofs:
Standard setup:
- Synthetic underlayment on entire roof (GAF Deck-Armor or Owens Corning ProArmor)
- Self-adhering ice & water shield in valleys
- Self-adhering ice & water shield at eaves (first 3-6 feet) in cold climates
- Drip edge installed properly
Why this works: Maximum protection, handles rain delays, strong warranty coverage, fast installation.
If You’re Stuck with Felt:
Best practices:
- Use 30# felt minimum (15# is too light and weak)
- Check 3-day weather forecast before starting
- Install and cover same day or next day if possible
- Have tarps ready if rain is forecasted
- Proper overlap: 2″ sides, 6″ ends, 4″ headlaps
- Fastener every 12-18 inches
Emergency tarp procedure:
- Use 6-mil poly tarps minimum
- Secure with boards weighted down—don’t nail through felt
- Ensure water sheds off, no pooling
- Remove tarps when work resumes
Real-World Scenarios I’ve Dealt With
Light Rain During Installation
What happened: Started felt installation at 7am. Pop-up shower at 2pm, about 40% of roof had felt down.
What I did:
- Stopped work immediately (wet felt is dangerous to walk on)
- Came back next morning
- Let felt dry until 11am
- Checked for damage—minor wrinkling, no tears
- Continued installation and got shingles on by end of day
Result: No issues. Roof is fine 8 years later.
Heavy Rain Overnight
What happened: Finished felt installation at 4pm. Plan was to start shingles next morning. Got 2 inches of rain overnight.
What I did:
- Arrived next morning to soaking wet, wrinkled felt
- Let it dry all day (took until 3pm in humid weather)
- Walked the roof—found multiple tears and severe wrinkling in several areas
- Replaced about 30% of the felt
- Started shingles the following day
Result: Extra day of labor, had to eat the cost of replacement felt. Learned my lesson about tarping.
Felt Exposed for 3 Weeks
What happened: Customer ran out of money mid-project. Felt sat exposed for 3 weeks in summer sun and got rained on twice.
What I did:
- Inspected when work resumed—felt was brittle, cracked, and weak
- Recommended complete replacement
- Tore off all felt and installed synthetic underlayment instead
- Proceeded with shingles
Result: Cost customer extra $800 for tear-off and new underlayment. Could have been avoided with tarping or using synthetic from the start.
Preventing Felt From Getting Wet
Based on hundreds of roofs, here’s what actually works:
Plan better:
- Check 3-day weather forecast religiously
- Don’t start if rain is coming within 24 hours
- Have a realistic timeline—if you can’t felt and shingle in one day, plan for tarping
Install correctly:
- Proper overlap prevents water infiltration
- Adequate fasteners (every 12-18″) prevent wind uplift
- Smooth installation without wrinkles
Work fast:
- The less time felt is exposed, the less can go wrong
- On a typical 1,500 sq ft house, I can do underlayment in one day and shingles in 2-3 days
- Minimize exposure window
Use better materials:
- Spend the extra money on synthetic—you’ll save it in labor and callbacks
- If you must use felt, use 30# not 15#
Have tarps ready:
- Keep 2-3 heavy tarps on every job site
- Weight them with boards and sandbags
- Takes 15 minutes to tarp a roof, can save you hours of repairs
FAQ – Quick Answers
Can I install shingles over damp felt?
No. The felt needs to be completely dry. Damp felt won’t bond with shingle adhesive properly and traps moisture.
How can I tell if felt is too damaged to use?
If it tears easily, has extensive wrinkling that won’t flatten, is brittle, or has been wet multiple times—replace it.
Is 30# felt better than 15# felt for wet conditions?
Yes. 30# is heavier, stronger, and more tear-resistant. It handles moisture better than 15#, but it still absorbs water.
Will felt dry out if it gets wet?
Yes, but it takes 12-48 hours depending on weather. It may be permanently wrinkled and weakened even after drying.
Can I leave felt exposed for a week?
In dry conditions, maybe. In wet or sunny conditions, you’re pushing it. Felt has a 2-7 day exposure rating. I don’t recommend it.
Should I use felt or synthetic underlayment?
Synthetic. It’s more expensive upfront but handles weather better, lasts longer exposed, and saves labor. The roofing industry has largely moved to synthetic for good reasons.
What if I can’t afford synthetic underlayment?
Then use 30# felt, work fast, watch the weather closely, and tarp if needed. Budget an extra day for potential drying time.
Bottom Line
Roofing felt can get rained on, but it’s not designed for it. Unlike synthetic underlayment, felt absorbs water, gets heavy, wrinkles, and weakens when wet.
My professional advice:
- If you’re planning a roof: Use synthetic underlayment. The extra cost ($50-100 more per square) is worth the peace of mind and better performance.
- If you’re using felt: Watch the weather forecast, work fast, install correctly, and have tarps ready.
- If your felt gets wet: Let it dry completely (12-48 hours), inspect for damage, replace damaged sections, and get shingles on ASAP.
- If felt has been wet multiple times or exposed over 2 weeks: Replace it. Don’t risk your roof’s integrity to save $200 in material.
The roofing industry moved to synthetic for a reason. Felt was the standard for decades, but better materials exist now. If you’re stuck with felt, you can make it work—just understand its limitations and plan accordingly.