RIDGELOCK PRO manufactures and exports synthetic roofing underlayment, ice & water shield, house wrap and radiant barrier. We serve distributors, contractors and private-label brands across North America, Europe and beyond — direct from the factory floor.
Published August 21, 2026 · RIDGELOCK PRO
Ask a roofer which underlayment they started using ten years ago, and most will say the same thing: asphalt-saturated felt. Ask the same roofer what they'd order today if the price were close, and the answer flips. Synthetic underlayment has moved from premium upsell to default spec in most of the US roofing market, and distributors who haven't adjusted their inventory mix are watching builders buy elsewhere.
If you distribute roofing materials — or you're a contractor trying to decide what to stock — this guide walks through what actually differs between the two products, which jobs genuinely call for felt, and what to look for when you're comparing synthetic rolls from a factory in China.
Asphalt-saturated felt (often called tar paper, or #30 / #40 felt by weight) did the job for a century because it was cheap, familiar, and good enough. A 30-pound roll covers roughly 4 squares, it lies flat, and it's been specified in building codes and roofer habits for generations.
But felt's weaknesses are not subtle once you look for them:
None of these are fatal. Felt roofs have been installed successfully for decades. But each one is a point of friction that synthetic underlayment was designed to remove.
Synthetic underlayment is a woven or spunbond polypropylene (PP) / polyethylene (PE) sheet, often coated or laminated for water resistance, with a slip-resistant surface for walkability. It's not a membrane and it's not a vapor barrier — it's a temporary weather barrier, same as felt, just engineered instead of saturated.
The differences that matter on a jobsite:
The trade-off is price: synthetic typically costs more per roll than felt at retail. But when you price per square of installed coverage and factor in the avoided tear-offs, dry-out days, and re-stapling, the gap narrows fast.
Synthetic isn't a universal upgrade. There are three situations where felt remains the sensible choice:
For everything else — new construction with unpredictable scheduling, metal roofs, steep slopes, coastal and high-rain regions — synthetic is the defensible spec, and it's what most distributors are reporting as their fastest-growing SKU.
Not all synthetic underlayment is equal, and this is where buying from a factory directly helps if you know the questions. When you're evaluating a product — or a supplier's spec sheet — check these five numbers:
One more thing to verify: the slip-resistant surface. A smooth synthetic sheet on a 7/12 roof is a liability claim waiting to happen. If the product doesn't have a textured face, it's not a roofing underlayment — it's a house wrap being sold as one.
The market signals are consistent across the US distribution channels we talk to:
If your inventory is still 80% felt, the question isn't whether to add synthetic. It's whether your competitors added it before you.
Felt isn't dead, and synthetic isn't right for every roof. But the direction of the market is unambiguous: builders spec synthetic first and reach for felt when the job demands it. The distributors who win the next few seasons will be the ones who carry both, know the difference, and can tell a contractor exactly why one product costs what it does.
If you're sourcing synthetic underlayment for your market and want to compare factory-direct pricing and specs — weights, tensile strength, UV ratings, and roll coverage — send us your target quantity and your region. We'll send back the numbers you need to make the call.
Send your target quantity and region — we'll reply with specs and wholesale pricing within one business day.