Posted on 2026-02-20 17:50:17

Underlayment is the quiet worker in a roof system. You don’t see it once shingles or panels go on, and you don’t think about it until a storm pushes water uphill, or an ice dam forms at the eaves, or the attic exhale turns into condensation beneath the deck. When those moments come, the choice you made under the shingles decides whether the roof shrugs it off or becomes a mess of leaks, stains, and callbacks.

I’ve torn off roofs where the shingles still looked decent but the deck was wavy and black because a cheap underlayment soaked through. I’ve also opened roofs after fifteen brutal winters and found the deck clean and tight because the roofer paired the right membrane with the right climate and roof covering. The difference shows up in the details: the material composition, how it’s fastened, where it’s layered, and how it interacts with the rest of the system, from ridge vents to gutters. If you’re planning a roof replacement, get your roofing contractor talking about underlayment early. It’s not an upsell, it’s the insurance policy you hope never to use.

What underlayment actually does

Think of underlayment as your roof’s second line of defense. Shingles or metal panels take the sun, wind, and hail. The underlayment manages what squeezes through and what builds up beneath. When it’s specified and installed correctly, it will:

Stop wind‑driven rain that sneaks under the primary roof covering, especially along rakes, valleys, and ridges. Serve as a temporary roof when unexpected rain hits mid‑install, or when a storm delays shingle delivery for a day. Separate resinous or chemically active wood decks, like cedar or some treated panels, from asphalt products that could bond or stain. Smooth minor deck imperfections so shingles lay flatter and seal more evenly. Control ice dam back‑up at eaves in cold regions by forming a watertight bond to the deck.

A good roofer treats each plane of the roof as a microclimate. Lower slopes see slower drainage, north slopes hold snow longer, and valleys carry concentrated water. Underlayment choice and placement should follow those realities, not a one‑size roll for every square foot.

The main types: what’s inside the rolls and where they excel

Most residential roofs in North America see three underlayment families: traditional asphalt‑saturated felt, synthetic polymer sheets, and self‑adhered ice and water membranes. Each has grades and quirks that matter on real roofs.

Asphalt‑saturated felt

The old standby, often labeled 15 lb or 30 lb. Modern 15 “pound” felt isn’t as heavy as it was decades ago, but the shorthand persists. It’s paper or fiberglass mat saturated with asphalt. It breathes a bit, it can wrinkle with moisture, and it tears more easily in high wind during installation.

Where it still earns its keep: steep roofs with full shingle coverage, underlayment installed and covered in the same day, mild climates, and budget‑conscious projects where you still want a proven layer. Thirty pound felt has better tear resistance and lies flatter than 15 lb. It’s also heavier to handle and a little slower to install.

If your roofing company suggests felt under a premium shingle in a hot climate, ask why. Felt can cook and become brittle under dark shingles on decks that run hot. I’ve seen brittle felt crack during nail‑gun recoil, creating micro‑paths for water.

Synthetic underlayment

Polypropylene or polyethylene weaves or scrims with coatings. These rolls are light, wide, and strong. Most synthetics have excellent tear resistance and stand up to extended UV exposure, which helps on big or complex roof installations where staging might leave an area uncovered for days. Many have textured walking surfaces that matter a lot on a 9/12 pitch with dew at sunrise.

Not all synthetics breathe. Some are vapor closed, which is fine in many assemblies but can trap moisture if attic ventilation is poor or if the deck has residual moisture from a recent rain. If your roofer tells you the attic ventilation is marginal, be cautious about fully non‑permeable synthetics across the entire deck. There are higher‑perm synthetics available that strike a better balance in those cases.

Expect a range in quality. A cheap synthetic can be slick when dusty and can delaminate if it bakes too long. A high‑grade synthetic will have marked nailing patterns, good fastener hold, and published exposure limits that match how real jobs unfold.

Self‑adhered ice and water shield

Rubberized asphalt or butyl adhesive membranes with a plastic or granular top. This is the workhorse for eaves in snow country and leak‑prone details like valleys, penetrations, and rake edges in high‑wind zones. It bonds to the deck, seals around nails, and creates a watertight layer that doesn’t rely on gravity alone.

Two important differences: adhesion chemistry and temperature flexibility. Butyl‑based membranes often perform better in heat and have lower odor during application. Asphalt‑based versions are common and reliable, but some can slump on hot south‑facing eaves if covered slowly. For metal roofs, look for high‑temperature ratings, often 240 to 250 F, to prevent membrane flow under panels.

When a roofer installs this product well, you won’t see fishmouths, bridging over seams, or trapped sawdust that prevents full adhesion. A sloppy install shortens the life of even the best brand.

Slope, climate, and covering: the triad that sets the spec

Any roofer who quotes underlayment without asking about slope, local weather, and roof type is guessing. The right membrane in the wrong context can still fail. Here’s how we weigh it on site.

Roof slope

Low slope, from 2/12 up to 4/12, sheds water slowly. Shingles will work in that range with special installation tweaks, but the underlayment becomes critical. I like a full‑deck self‑adhered membrane on 2/12 to 3/12, or at least lapped and sealed synthetic with tight fastener patterns and taped seams that the manufacturer approves. Above 4/12, synthetics and felt both perform, but wind exposure pushes me toward synthetics for their tear resistance.

Ultra‑steep slopes, 10/12 and up, put installers at risk and magnify wind draw. A grippy synthetic buys safety and reduces displacement during sudden gusts. I always budget a few extra cap nails in those sections to keep the membrane taut and quiet during the night, because flapping underlayment scuffs the deck and wakes the neighborhood.

Climate

Cold and snow: Ice dams drive the spec. Most codes in snow belts call for self‑adhered ice and water shield from the eaves to a point at least 24 inches inside the warm wall line. On deep overhangs, that can mean two or even three courses. Valleys and dead‑end walls get the same treatment. Above that, a quality synthetic handles the field.

Hot and sunny: High deck temperatures punish membranes. Choose synthetics with high UV exposure ratings and heat tolerance. If you are installing under a dark shingle on a south‑facing slope, ask your roofing contractor for a product data sheet that lists maximum exposure time and temperature stability. Paying a small premium for a high‑temp rated synthetic often saves money on callbacks where cheap synthetics wrinkle under thermal movement.

Wind and storms: In hurricane or prairie wind regions, fastener schedules and underlayment tear strength matter. We use synthetics with printed nail patterns and back that up with cap nails rather than staples. Along rakes, a strip of self‑adhered membrane under the drip edge and over the first course of synthetic creates a belt and suspenders approach.

Humidity and rain: If afternoon storms surprise you every other day, look for synthetics that can serve as a temporary roof for 60 to 90 days. Taped seams are helpful, but only if the tape is compatible and installed on clean, dry laps. I keep microfiber cloths in the tool bag to wipe dust before taping. It sounds fussy, but it stops leaks.

Primary roof covering

Asphalt shingles: Pair easily with most synthetics and felt. I prefer synthetics for strength and safer footing during roof installation. Under premium designer shingles that weigh more, a heavier synthetic or 30 lb felt reduces telegraphing of deck imperfections.

Metal panels: Metal gets hot. Use high‑temperature rated underlayment and a full ice and water shield in valleys and at eaves in snow regions. On standing seam, butyl‑based self‑adhered membranes under pans at eaves mitigate condensation and ice back‑up. Avoid low‑temp asphalt membranes that can ooze onto panel backs and bond in the heat.

Cedar shakes: Most cedar systems call for interlayment felt between courses. Check the manufacturer’s spec. Under the base layer, a breathable synthetic or traditional felt helps the deck dry. Avoid fully impermeable membranes across the entire deck unless the assembly is vented generously.

Tile and slate: Heavy materials with long service life deserve a robust underlayment, often double layers or premium synthetics rated for decades of service. If this is your forever home, talk with your roofer about underlayments designed for 30 to 50 years under tile, and get that in writing.

Code requirements and what they don’t tell you

Building codes set a minimum. They usually address ice barriers in snow regions, acceptable underlayment types, and lapping. They rarely speak to wind uplift along rakes on a bluff, or the way sun hits a black deck at 3 p.m. on a July afternoon in Texas. A roofing company that works your area will know the local quirks the code book misses.

Two code details to watch:

Ice barrier extent: The “24 inches inside the heated wall” rule depends on overhang depth. If you have a 12‑inch overhang and a 4/12 slope, two courses of 36‑inch ice and water shield can land you short. Your roofer should calculate the run on your pitch to make sure coverage reaches far enough. Underlayment for low slope: Many codes require double coverage, which means a half‑lap installation that creates two layers. Few homeowners realize how much labor that adds. If you see a low price for a low‑slope section, ask how the crew will meet the coverage requirement.

Fasteners, laps, and sequencing matter more than brand names

I have used off‑brand synthetics that outperformed premium labels because the crew nailed them right, lapped them shingle‑style, and kept the deck clean. Underlayment fails at edges and seams first. Pay attention to these practices during your roof replacement:

Use cap nails, not staples, on synthetics in windy areas. Staples slice fibers and can tear under flapping loads. Cap nails spread the load and seal better. Follow printed nailing patterns. If the roll says every 12 inches at laps and staggered in the field at 24 inches, do that. Guessing wrong cuts wind rating in half. Lap high over low, always. In valleys, run the underlayment from each plane past the centerline, then cap the valley with self‑adhered membrane. If you start with the valley membrane then lap synthetics over it from both sides, water can track under your lap in a wind‑driven rain. Keep laps clean and dry. Dust and saw kerf can prevent tape and adhesive from grabbing. On a tear‑off, blow the deck, then roll. If a brief sprinkle hits, squeegee and towel the laps before sealing. Sequence penetrations early. Skylights, plumbing vents, and chimneys should get their ice and water wraps before the field underlayment reaches them, not after. That way the laps always shed water.

These are the little things that separate a careful roofer from a rushed crew. They don’t add much time, but they deliver a quieter roof in a storm.

Budget conversations without the surprises

Homeowners often ask where to spend and where to save. Underlayment falls into a category where a moderate upgrade pays off more than you expect, but only to a point. Here’s how I frame the choices during a roof installation estimate:

If you are in a warm, low‑wind region with simple gables, a mid‑grade synthetic underlayment and standard ice and water shield at penetrations and valleys usually balances cost and protection. In snow country, invest in wide ice and water coverage at eaves and valleys. Don’t skimp on cap nailing and edge seals. The budget impact is modest compared to drywall repairs and insulation drying after an ice dam event. On low slopes near the shingle minimum, consider full‑deck self‑adhered membranes or a synthetic with taped seams that the manufacturer approves as a secondary water barrier. This is not showy work, but it stops 90 percent of nuisance leaks. For long‑life coverings like tile, select an underlayment that matches the lifespan. The extra cost is meaningful, but it avoids tearing off tile later just to replace a failed membrane.

A reputable roofing contractor will line‑item the underlayment in your bid. If it’s a single vague line, ask for product names, coverage locations, and exposure limits. It’s your house. You deserve to see Roof replacement specifics.

Real‑world examples from the tear‑off pile

A cedar colonial we reroofed had a hot south‑facing 6/12 slope. The previous roofer had laid 15 lb felt under heavy dimensional shingles. Eight summers later, the felt turned brittle and fractured around nail lines. Wind‑driven rain found the pathways, staining ceilings below. The shingles themselves were fine. We replaced the underlayment with a high‑temp synthetic and left the same shingle profile. Twelve years on, no callbacks. Same roof deck, two different outcomes based on the layer you never see.

Another case, a ranch under maples with a shallow 3/12 pitch. The homeowner wanted to save by skipping full‑deck ice and water shield. We negotiated a compromise: a robust synthetic with taped seams and ice and water at all eaves and penetrations. The following spring, a late March thaw met a flash freeze. Gutters formed ice lips, and water sat for a day. The ceiling stayed dry, and the homeowner sent us a note afterward saying the upgrade was worth every dollar. If they had chosen basic felt, I doubt that story would have ended the same way.

Compatibility with gutters and edge metal

Underlayment meets the world at the edges, which is where gutters live and where wind and water first collide with the roof line. A good gutter company loves roofers who think about this junction.

Drip edge goes on top of the underlayment along rakes and under the underlayment along eaves, unless the local code or shingle manufacturer states otherwise. In ice country, we run the self‑adhered membrane out to the fascia and fold it slightly into the gutter trough line. That way, water that backs up under the shingle nose still meets a watertight surface that leads it into the gutter, not behind it. If your roof repair history includes fascia rot near downspouts, ask your roofer to show you this detail in person before shingles go on.

On reroofs with existing gutters, protect the gutter coating during tear‑off and underlayment installation. Granular ice and water shield can scratch factory finishes. We tape foam pads over gutter fronts where the crew slides rolls and keep a trash chute, not a free fall of old shingles, near the downspouts.

Moisture management from the inside out

Underlayment can only do so much if the attic is a sauna. Before the roof replacement starts, your roofer should peek inside the attic and look for:

Adequate intake and exhaust ventilation that matches the roof’s geometry. A continuous soffit and ridge vent pair is ideal on simple gables. On hip roofs or chopped‑up plans, a mix of hip vents and baffled intakes can make more sense. Bath fans actually vented outside, not into the attic. A surprising number end in the soffit or under insulation. That moisture will find your underlayment on cold nights and condense. Signs of prior condensation, like rusty nail tips and damp sheathing at the ridge. If present, a slightly more vapor‑open underlayment can help, but it’s secondary to fixing the airflow.

When I see poor ventilation and a plan to use a fully non‑permeable synthetic across the whole deck, I slow the conversation down. We either improve ventilation or choose an underlayment that allows some drying to the exterior. A strong roofer owns that judgment call and explains the trade‑offs.

Installation timing and UV exposure

Underlayment sometimes sits in the sun while the crew stages, replaces bad decking, installs new flashing, and waits for weather. Synthetics advertise exposure ratings, commonly 60 to 180 days. That’s not a dare to leave it uncovered for a season, but it does give breathing room on big projects or when a sudden storm interrupts work.

Ask your roofer how they manage partial days. A common best practice is to complete a slope at a time: deck repair, underlayment, edge metal, starter, and at least the first course of shingles before the crew moves. If a storm rolls in, that slope is in a defensible position. I’ve seen teams roll underlayment across the whole house at once, then scramble as clouds build. It’s faster until it isn’t. The right roofing company won’t chase speed at the cost of risk.

Warranties and the fine print

Manufacturer warranties on shingles often include language about acceptable underlayments and how they should be installed. If you want the top‑tier wind warranty, for example, the spec might require a particular synthetic, an ice and water shield at all eaves, and cap nails at specific spacing. Your roofer should align the underlayment choice with the shingle warranty you’re buying, not just the local code.

Labor warranties from the roofer matter, too. If a leak traces back to a missed lap or a bad fastener pattern, the product warranty won’t help. A contractor who is proud of their underlayment work will stand behind it in writing for a realistic period, often 5 to 10 years.

Questions to ask your roofer before signing

Use this quick set of prompts to get a clear picture and to compare bids apples to apples.

Which underlayment products are you proposing for the field, eaves, valleys, and penetrations, and why those? What is the exposure rating and temperature rating for each, and how will you sequence work to stay within limits? How far will the self‑adhered membrane extend from the eaves relative to my interior wall line on each slope? What fasteners will you use, and what is the nailing pattern? How will you protect existing gutters and tie underlayment into drip edge and rake edge metal for wind and ice?

If a roofer answers these confidently, with brand names and details, you’re likely in good hands. If they wave it off as “standard,” press for specifics. A clear plan here prevents surprises later.

When a roof repair is smarter than a full replacement

Occasionally the call is not to replace the entire roof, but to fix a chronic leak by upgrading the underlayment in a specific zone. Valleys that see leaf loads, eave sections beneath tall pines, or a chimney saddle that catches snow can often be stripped to the deck, rebuilt with self‑adhered membrane and new flashing, and tied back into sound shingles. This is precision work. If your roofer has a dedicated repair crew, ask for their assessment before you commit to a full roof replacement. It’s not about avoiding the new roof, it’s about timing it right and addressing the weak link without throwing away years of remaining life.

The bottom line from the field

Roofs fail at the margins and at the joints. Underlayment, chosen well and installed with care, turns those weak points into quiet non‑events. Match the membrane to your slope, weather, and covering. Respect the eaves in snow country and the sun in hot climates. Nail where the roll tells you. Keep laps clean and lapped in the right direction. Tie into drip edges and gutters like water is hunting for a shortcut, because it is.

A seasoned roofer or roofing company will treat underlayment as part of a system that includes attic ventilation, deck condition, flashing, and even gutter performance. That mindset does not show up on a curbside drive‑by estimate, but it will show up five winters from now when your ceilings are still pristine. If you are interviewing contractors for a roof installation or considering a targeted roof repair, use the underlayment conversation to gauge their craft. The best answers sound practical, not salesy, and are backed by real products, local experience, and a willingness to show you the work in progress.

<!DOCTYPE html> 3 Kings Roofing and Construction | Roofing Contractor in Fishers, IN

3 Kings Roofing and Construction

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Name: 3 Kings Roofing and Construction

Address: 14074 Trade Center Dr Ste 1500, Fishers, IN 46038, United States

Phone: (317) 900-4336

Website: https://3kingsroofingandgutters.com/

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Saturday: 7:00 AM – 1:00 PM
Sunday: Closed

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3 Kings Roofing and Construction provides professional roofing services in Fishers and the greater Indianapolis area offering commercial roofing installation for homeowners and businesses.

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Landmarks Near Fishers, Indiana

Conner Prairie Interactive History Park – A popular historical attraction in Fishers offering immersive exhibits and community events.
Ruoff Music Center – A major outdoor concert venue drawing visitors from across Indiana.
Topgolf Fishers – Entertainment and golf venue near the business location.
Hamilton Town Center – Retail and dining destination serving the Fishers and Noblesville communities.
Indianapolis Motor Speedway – Iconic racing landmark located within the greater Indianapolis area.
The Children’s Museum of Indianapolis – One of the largest children’s museums in the world, located nearby in Indianapolis.
Geist Reservoir – Popular recreational lake serving the Fishers and northeast Indianapolis area.

Roofer Tips for Choosing the Right Underlayment in Roof Replacement