Best Soundproof Underlayment for Hardwood Floors, by Install Type

If you’re choosing the best soundproof underlayment for hardwood floors, start with how the boards will be fastened, because nailed, glued and floating floors each take a different acoustic underlayment.

Buy on the biggest number on the roll and you can end up with a pad your flooring maker doesn’t allow, or an IIC rating earned on a concrete slab with a ceiling hung below it.

Get the match right and the layer takes the hard slap out of footsteps for the people downstairs and some of the hollow click out of your own room.

The picks come first, then what IIC and STC measure, why one roll lists ratings from 55 to 71, and how nail-down, floating and moisture rules narrow the choice.

Start with the table, which matches each pick to the way your floor goes down.

Which Is the Best Soundproof Underlayment for Hardwood Floors?

That table puts the install rule first, because it decides more than any rating does. The best soundproof underlayment for hardwood floors is FloorMuffler UltraSeal for nailed or glued boards, QuietWalk for floating engineered wood and QEP’s 6 mm cork for glued or floating floors over concrete, with two Roberts pads as lighter floating options.

Pick	Installs its maker or listing approves	Published ratings	The floor behind the numbers
FloorMuffler UltraSeal, 2 mm foam	Floating, nail-down and double glue-down, under laminate, engineered and solid hardwood	IIC up to 74, STC up to 73, delta IIC up to 25	Not named in its Amazon listing
QuietWalk, 3 mm recycled fiber	Floating only	IIC 57 to 61 under engineered wood, 71 under laminate	Ceiling assemblies and wood frames topped with gypsum concrete
QEP natural cork, 6 mm	Glued both ways or floating	IIC 74, STC 70, delta IIC 22	Ceramic tile on a 6-inch concrete slab
Roberts Black Jack, 2.5 mm foam	Floating laminate, bamboo and engineered wood	IIC 70, STC 66, delta IIC 21	Not named on Roberts’ data sheet
Roberts First Step, 2 mm, three layers	Floating laminate and engineered hardwood	IIC 68, STC 67, delta IIC 20	Not named in Roberts’ product guide

Read the last column before the middle one. Delta IIC, the figure the standard method measures on a bare concrete test floor, runs only from 20 to 25 across these rolls, so they’re closer than their headline IICs suggest.

The descriptions come from the makers’ manuals and spec pages. Every pick met Burton Acoustix’s rating, review and stock checks on 27 October 2026.

A pad is only one of three levers, and our guide to the best floor soundproofing sets these ratings beside carpet and the ceiling below. The rest of this page explains the numbers in that table, then gives each pick’s install rules in detail.

What Does an Acoustic Underlayment Do Under Hardwood?

Those IIC figures measure one job above all, which is keeping footsteps out of the room below. An acoustic underlayment, sold as an acoustic membrane or acoustic underlay too, is a resilient layer between the boards and the subfloor that cushions each impact before it reaches the structure.

Hardwood needs that cushion more than most floors. NRC Canada’s Construction Technology Update No. 35, its guide to impact sound through floors, says concrete slabs with a hard surface such as tile, marble or hardwood rate low and are always judged unacceptable, and that wood flooring on concrete does only slightly better than the bare slab.

Its table for a 150 mm (6-inch) concrete slab shows how much a resilient layer changes that:

Floor on a 150 mm concrete slab	Approximate IIC
Bare, or ceramic or marble tile	28
Hardwood flooring	30 to 35
9 mm hardwood on a 6 mm resilient layer	45 to 50
Plywood on wood strapping over 25 mm of mineral fiber board	50 to 55
Carpet and underlay	75 to 85

The jump from 30-35 to 45-50 is the underlayment’s whole job in one row. NRC says wood flooring on a resilient layer can give acceptable impact insulation, and it names shredded or foamed rubber, foamed plastic and cork mats as the materials commonly used.

Thickness helps up to a point. In NRC’s words, a thicker resilient layer usually, but not always, raises the IIC, and the material itself matters most.

Voices and TV are a different problem from footsteps. The airborne rating, STC, belongs to the whole floor and ceiling, which is why one roll’s STC can swing by 16 points between test floors, as the next two sections show.

A pad also changes the sound inside your own room. Roberts says its Black Jack foam helps absorb everyday in-room noise, the hollow click that hard floors make underfoot.

Don’t confuse foam underlayment with acoustic foam, though. Foam underlayment is a thin, dense sheet made to sit under flooring, while the open-cell panels in our guide to the best soundproof foam treat echo on walls and block little sound.

What Do IIC and STC Mean on an Underlayment Label?

The NRC numbers above are IIC ratings, and every roll in the first table quotes one beside an STC. IIC, impact insulation class, rates how well a whole floor-ceiling assembly keeps a standard tapping machine’s hammer blows out of the room below, and STC, sound transmission class, rates how well it blocks airborne sound such as voices; on both, a higher number is better.

Both come from ASTM standards. ASTM E492 is the laboratory impact test, run with the tapping machine that NRC describes as five steel-faced hammers striking the floor, and ASTM E989 turns its results into the IIC rating.

The airborne side works the same way. ASTM E90 measures sound transmission loss through partitions, floor-ceiling assemblies included, and ASTM E413 turns that into the STC.

Delta IIC is the number built for comparing underlayments. ASTM E2179 measures how much a floor covering cuts tapping-machine noise through a standard concrete floor in a laboratory, and Roberts calls the delta rating the only true measure of a product’s own sound reduction, as opposed to a floor assembly’s.

E2179 has two limits worth knowing. It applies only in the lab, not to a floor in a building, and ASTM notes that its results aren’t necessarily related to how people judge a floor covering.

A test in your own building uses ASTM E1007, whose ratings are AIIC, ISR and NISR. Laguna Woods Village, a California condominium community, warns owners in its flooring Standard 11A that field results can run 3 to 5 dB below laboratory ones.

Codes set the minimum for floors between homes. Roberts’ product guide gives 50 as the minimum IIC and STC under the International Building Code, and the Laguna Woods standard says California’s building code sets IIC 50 and AIIC 45 as minimums.

One more rating matters under wood framing. ASTM E3207 defines LIIC, a low-frequency impact rating for the thudding that footfall produces on lightweight structures, and NRC makes the same point about the tapping machine, which doesn’t accurately reproduce people walking, least of all the thump below 100 Hz on a lightweight joist floor.

Rating	Test standard	What it tells you
IIC	ASTM E492, rated by E989	Footstep and impact noise through a whole floor-ceiling assembly, in a lab
STC	ASTM E90, rated by E413	Airborne sound such as voices through a partition or floor-ceiling, in a lab
Delta IIC	ASTM E2179	How much a floor covering improves a bare concrete test floor, in a lab
AIIC, ISR, NISR	ASTM E1007	Impact noise through a finished floor in a building
LIIC	ASTM E3207	Low-frequency thudding from footfall on lightweight floors

Of these, delta IIC is the one that compares rolls fairly. The field ratings are the ones a condo board or a neighbor’s complaint will use.

Why Does a Rating Change With the Floor Under It?

Because IIC and STC belong to the assembly, one roll earns a different score on every test floor. MP Global’s June 2025 spec sheet for QuietWalk shows it plainly: the same 3 mm pad lists IICs from 55 to 71, depending on the flooring above it and the structure below.

Flooring on QuietWalk	Floor and ceiling below	IIC
Laminate	With a ceiling assembly	71
Laminate	With a suspended gypsum board ceiling	68
Floating engineered hardwood	Wood frame, gypsum concrete and isolation clips	61
Laminate	No ceiling assembly, field test	60
Engineered wood	UL L521 wood frame with 3/4-inch gypsum concrete	59
Floating engineered hardwood	Wood frame and gypsum concrete	59
Floating engineered wood	With a ceiling assembly	57
Laminate	6-inch concrete slab, no ceiling assembly	55

The headline 71 is laminate with a ceiling below, and every engineered wood row sits between 57 and 61. The sheet’s STC rows move the same way, from 66 for floating engineered wood over a suspended gypsum board ceiling down to 50 for laminate on a bare 6-inch slab.

The Laguna Woods standard puts the consequence in one line: a maker’s IIC is valid only when the tested assembly matches the floor in the building. So compare delta IICs between rolls, and trust an IIC only when its test floor looks like yours.

Amorim’s AcoustiCORK S130 sheet shows the same effect from another angle. Its 1/2-inch cork rated IIC 50 under ceramic tile on an 8-inch hollow-core slab with no ceiling in the lab, while field tests on an 8-inch concrete slab with no ceiling gave 54 under tile and 56 under hardwood.

QEP’s cork figures carry the same caveat. Its IIC 74 and STC 70 come from ceramic tile on a 6-inch cement slab, not from hardwood on joists.

How Much Can a Pad Help a Wood-Joist Floor?

Nearly every test floor in that table is concrete or topped with gypsum concrete, and a house with a plywood subfloor on wood joists behaves differently. NRC Canada’s figures show how little a thin resilient layer moves the rating there: on a basic joist floor rated IIC 45, hardwood alone rated 47 and hardwood on a 6 mm resilient layer also rated 47.

Topping on a basic wood-joist floor (IIC 45)	Approximate IIC
Ceramic or marble tile	40
Hardwood flooring	47
9 mm hardwood on a 6 mm resilient layer	47
Plywood on wood strapping over 25 mm of mineral fiber board	55 to 58
Carpet and underlay	75 to 85

The reason is frequency. NRC explains that most of the sound setting a joist floor’s IIC lies below 250 Hz, so resilient coverings that lift the rating on concrete do much less on joists with wood subfloors.

People below notice it too. NRC reports complaints of booming and thumping from footsteps on joist floors even when the IIC is above 50, the low-frequency thud ASTM E3207’s LIIC rating was written for.

The thin pad still earns its place. NRC found that toppings on a joist floor do cut impact noise at high frequencies, the sharp end of each footstep, even though they leave the IIC almost unchanged.

What moves a joist floor’s rating is mass and separation. NRC found that doubling the subfloor’s mass raised the IIC from 45 to 47 and doubling the ceiling’s as well brought it to 52, and it calls resilient support for the ceiling’s gypsum board essential, because board fixed straight to the joists gives very poor impact insulation.

That ceiling work happens below the subfloor, and our step-by-step guide to soundproofing between floors from above and below covers it. On joists, then, choose the pad for the install method and moisture, and expect its gain to come as a quieter, less clicky floor rather than a big jump in IIC.

Does a Thicker Underlayment Block More Noise?

If a 6 mm layer barely moves a joist floor, it’s fair to ask whether a thicker one would. Not reliably: across Roberts’ own range, delta IIC climbs only from 20 to 24 between 2 mm and 12 mm, and 1.5 mm of rubber matches the 6 mm cork at 22.

Roberts underlayment	Material	Thickness	IIC	STC	Delta IIC
SoundBarricade	Rubber with recycled tire crumb	1.5 mm	68	63	22
First Step	Polystyrene beads between two films	2 mm	68	67	20
Quiet Cushion	Cross-linked foam	2 mm	71	67	21
Black Jack	Closed-cell foam	2.5 mm	70	66	21
Super Felt	Heat-treated recycled fibers	3 mm	67	66	21
Natural cork	Cork	6 mm	74	70	22
Natural cork	Cork	12 mm	71	62	24

Roberts’ guide doesn’t name the test floors behind these figures, so read the pattern rather than single points. The pattern matches NRC’s finding that the IIC depends mostly on the resilient material used, with thickness a second factor that usually, but not always, helps.

Density varies more than the labels suggest. SoundBarricade’s rubber weighs 25 lb per cubic foot against 11.52 lb for QuietWalk’s fiber and 11.5 to 13.6 lb for Amorim’s AcoustiCORK, so 1.5 mm of that rubber comes to about 2 ounces per square foot, the same as QuietWalk’s 3 mm at 1.92.

Firmness matters as much as cushion under a floating floor. Roberts lists resisting compression among the qualities that support and protect a floating floor’s locking system, and MP Global gives QuietWalk’s compression resistance as 85.5 psi at 50% compression, by ASTM D1667.

So take thickness from the flooring maker’s instructions rather than the roll’s label. Diamond W, for one, names the pads it recommends under its floating floors: Eternity’s Seal Guard Zero VOC, MP Global’s Sound Buffer or QuietWalk.

Can You Nail Hardwood Through an Acoustic Membrane?

Those flooring makers’ instructions also decide whether a pad can go under nails, and solid boards on joists are usually nailed. You can nail hardwood through an acoustic membrane only when its maker approves nail-down use, as Roberts does for its SoundBarricade rubber under nailed and stapled hardwood and as FloorMuffler’s listing does for UltraSeal.

Other makers rule it out. MP Global’s QuietWalk sheet lists mechanically fastened flooring and glued-down flooring among the floors it isn’t suitable for, and QEP says never to mechanically fasten its cork, because doing so severely diminishes its acoustic performance.

The usual layer under nailed hardwood isn’t an acoustic product at all. Stonewood’s solid hardwood instructions call for #15 black felt paper laid over the entire floor, under boards nailed with cleats or staples to a wood subfloor, and Diamond W’s engineered flooring instructions specify 15 lb felt per ASTM D4869, lapped 6 inches, as a moisture barrier.

Roberts’ product guide sells a 30 lb kraft paper for the same spot, to ease installation and minimize squeaks under nail-down floors. Squeak control is a real gain, though Roberts’ guide gives that paper no sound rating.

If you do nail through a sound underlayment, the nailer setting matters. Roberts’ SoundBarricade installation guide says to adjust the nail gun’s air pressure so the nail or staple is firmly set but doesn’t fully compress the underlayment.

SoundBarricade itself is 1.5 mm of rubber blended with recycled tire crumb, at 25 lb per cubic foot. Roberts’ data sheet rates it IIC 68, STC 63 and delta IIC 22 under laminate or wood, and approves it for floating, stapled, nailed and double glue-down installs.

Check the flooring maker’s instructions as well. Roberts ties its own underlayment warranty to following them, and Stonewood warns that improper installation may void its floor’s warranty.

Is a Floating Hardwood Floor Quieter?

Nailing is one of three ways to fix engineered boards, and floating skips fasteners altogether. A floating floor can be the quieter choice for the room below, since NRC’s best wood result in either table comes from a floating build, but Diamond W warns that a floating engineered floor will sound hollow and may squeak, since nothing glues or fastens it to the subfloor.

Diamond W adds that the hollow sound isn’t a manufacturing defect, just the way a floating floor is built. That hollow sound is the in-room noise a pad like Black Jack is sold to soften.

NRC’s guide calls a true floating floor, a rigid layer on a resilient mat or fiber board, the most practical way to get high impact insulation under a hard finish such as hardwood. Its wood example is heavier than any roll here, plywood on wood strapping over 25 mm of mineral fiber board, which rated 50 to 55 on a concrete slab and 55 to 58 on joists.

Edges matter on any floating floor. QuietWalk’s sheet says to keep the pad 1/2 to 3/4 inch from the walls, and QEP and Amorim both call for a perimeter isolation strip so the finished floor never touches the walls or fixed objects.

Seams matter too. MP Global says to butt QuietWalk’s seams and seal them with its lip and tape or a similar moisture-resistant tape, and QEP tapes its cork seams and the wall joint so the layer stays put while the floor goes down.

Does Engineered or Solid Wood Change the Choice?

Floating is open only to some boards, and that’s where engineered and solid wood part ways. Yes, the wood decides the list: Diamond W’s instructions cover nailing, gluing and floating its engineered boards, while Stonewood’s solid boards are nailed or stapled over a wood subfloor, so a solid floor needs a layer rated for nails.

Grade and heat narrow it further. Stonewood keeps its solid floors to rooms on or above grade and advises against radiant-heated subfloors, while Diamond W allows its engineered floors on, above or below grade.

That makes a basement or a slab a job for engineered wood, and it opens the whole floating list. QuietWalk, Black Jack and First Step are all sold for floating engineered floors, and QEP’s cork takes a glued engineered floor as well.

For solid boards, FloorMuffler UltraSeal is the carded pick whose listing names solid hardwood and nail-down installs. SoundBarricade is the rubber alternative that Roberts approves for nailed hardwood.

Stonewood also sets the subfloor for its solid boards. It asks for at least 5/8-inch plywood or 23/32-inch OSB over joists 16 inches apart, the deck any nail-rated pad would sit on.

Do You Need a Moisture Barrier Under Hardwood?

Basements and slabs bring the next rule, which is moisture. Over concrete you do: Diamond W requires a moisture barrier over every concrete subfloor, and each pad sets its own moisture limit, measured with a calcium chloride test.

Here’s how the makers’ limits compare for concrete under their pads:

Underlayment	Moisture limit over concrete, per 1,000 sq ft in 24 hours	What the maker says to do above it
QuietWalk	5 lb	Add a concrete sealant or a polyethylene vapor barrier
SoundBarricade	3 lb, by ASTM F1869	An additional moisture barrier may be required
QEP natural cork, under wood	3 lb	Corrective action must be taken

QEP’s guide also gives the order for a floating floor. If the flooring maker asks for a vapor retarder over concrete, lay a 6-mil sheet such as Roberts’ Moisture Barricade first, then the cork.

Several pads carry their own film. QuietWalk has a polyethylene vapor barrier with a perm rating of 0.19 and goes down barrier side up, FloorMuffler’s listing names a built-in moisture barrier with a lip-and-tape seam, and Black Jack and First Step have overlap film and an adhesive strip to seal the seams.

Wood subfloors get a lighter layer. Roberts’ product guide says its 6-mil Moisture Barricade exceeds NWFA requirements over concrete and that its silicone-treated paper meets NWFA perm ratings over wood subfloors, the spot felt paper fills under nailed floors.

Radiant heat is the other case to check. QuietWalk’s sheet approves it for in-floor heating, QEP says its cork increases the effectiveness of floor heating systems, and Stonewood rules out radiant-heated subfloors for its solid boards.

How Do the Picks Differ on Nails, Glue and Moisture?

With the install, the joists and the moisture settled, each pick below comes with its own rules from its maker or listing. The picks differ mainly in what may go on top of them and how, and only then in their published ratings.

Check four things on any roll before you order it:

• the install methods its maker approves, matched to how your boards go down
• the test floor behind its IIC and STC, matched to your slab or joists
• its delta IIC, the fair comparison between rolls
• its moisture limit over concrete, and whether it carries its own film

The sections below answer those four questions for each roll, starting with the one pad on the list that takes nails.

FloorMuffler UltraSeal, for Nailed, Glued or Floating Floors

For a solid floor that will be nailed, FloorMuffler UltraSeal Underlayment 300SF is the carded pick that its listing approves for floating, nail-down and double glue-down installs under laminate, engineered and solid hardwood. It’s 2 mm of cross-linked polypropylene foam with a built-in moisture barrier and a self-sealing lip and tape for the seams.

FloorMuffler UltraSeal Underlayment 300SF

Coverage: 300 sq ft

Thickness: 2 mm

Material: Cross-linked polypropylene foam

Installs: Floating, nail-down, double glue-down

✓ For floating, nail-down and double glue-down installs✓ Made for laminate, engineered and solid hardwood

See ratings on Amazon

The listing gives IIC up to 74, STC up to 73 and delta IIC up to 25, without naming the floors behind them. Those figures read as the top of a range, so ask for the test report on a floor like yours before you lean on one, the same check the QuietWalk table showed is worth making.

On joists, the NRC numbers from earlier still apply, so expect UltraSeal to quiet the click of heels more than the thud of walking. Borrow Roberts’ nailer advice for its own rubber pad too: set each fastener firmly without crushing the layer.

QuietWalk, for Floating Engineered Wood

For a floating engineered floor, QuietWalk Underlayment 360 sq ft is the best-documented roll here, because MP Global’s sheet names the test floor behind every number. It’s 3 mm of recycled synthetic fibers with a polyethylene vapor barrier, sold for laminate and hardwood floors and approved for floors with a pre-attached pad.

QuietWalk Underlayment 360 sq ft

Coverage: 360 sq ft

Thickness: 3 mm

Material: Recycled fiber with a vapor barrier

Install: Floating

✓ 3 mm recycled fiber with a built-in vapor barrier✓ Made for laminate and hardwood, approved for floors with a pre-attached pad✗ For floating floors, not nailed or glued ones

See ratings on Amazon

Under engineered wood, its IICs run from 57 with a ceiling assembly to 61 on a wood frame with gypsum concrete and isolation clips, and its delta IIC is 24 under laminate. MP Global rules it out for glued-down and mechanically fastened floors, so it’s a floating-only pad.

Its sheet accepts dry, fully cured concrete at least 28 days old, up to the 5 lb moisture limit in the table above. It’s also approved for in-floor heating, and the 360 sq ft roll is 6 ft wide by 60 ft long.

QEP Natural Cork, for Glued or Floating Floors on Concrete

For engineered boards glued over a slab, or floated over one, QEP 72000Q Natural Cork Underlayment (6 mm) is the cork pick, a 4 by 50 ft roll that QEP sells for glued wood flooring and floating floor systems as well as tile. Its natural cork product page lists IIC 74 and STC 70 under ceramic tile on a 6-inch cement slab, with a delta of 22.

QEP 72000Q Natural Cork Underlayment (6 mm)

Coverage: 200 sq ft

Size: 4 x 50 ft

Thickness: 6 mm

Material: Natural cork

✓ IIC 74 and STC 70 with ceramic tile on a 6 in. cement slab, delta 22✓ 6 mm natural cork that also works as a crack-isolation layer✗ Its ratings are for tile on concrete, not hardwood on joists

See ratings on Amazon

QEP also sells the cork as a crack-isolation layer that resists the transfer of stress cracks up to 1/8 inch, and says it reduces thermal transmission. For a glued floor, its installation guide double-bonds the layer: the cork is troweled down with wood flooring adhesive and rolled with a 100 lb roller, then the wood is glued to the cork.

It never takes nails, since QEP says mechanical fastening severely diminishes its acoustic value. QEP also recommends waiting at least 24 hours after the cork goes down before installing the finished floor.

Roberts Black Jack, a Closed-Cell Foam for Floating Floors

For a floating engineered or bamboo floor, ROBERTS Black Jack Underlayment is 2.5 mm of dense closed-cell foam that Roberts makes for floated laminate, bamboo and engineered wood floors. Roberts rates it IIC 70, STC 66 and delta 21 without naming the test floor.

ROBERTS Black Jack Underlayment

Coverage: 100 sq ft

Size: 43 in. x 28 ft

Thickness: 2.5 mm

Material: Closed-cell foam

✓ 2.5 mm closed-cell foam for floated laminate, bamboo and engineered wood✓ Overlap and adhesive strip seal out moisture and join rolls✗ Sold for floated floors only, not nailed or glued ones

See ratings on Amazon

Roberts says the foam helps absorb everyday in-room noise, the hollow sound Diamond W warned about on floating floors. It resists moisture, mold and mildew, has an overlap film and adhesive strip to seal the seams, and Roberts lists it for use above, on and below grade.

Roberts sells it only for floated floors, so skip it for nailed or glued boards. Its delta of 21 sits close to QuietWalk’s 24, so the choice between them comes down to fiber or foam and to which test floors you can check.

Roberts First Step, a Three-Layer Floating Pad

For a floating floor over a slab or a plywood subfloor, ROBERTS First Step Premium Underlayment is Roberts’ three-layer pad: a clear bottom film, a core of extruded polystyrene beads and a green moisture barrier on top, 2 mm in all. Roberts approves it for floating laminate and engineered hardwood over concrete, plywood and properly prepared OSB.

ROBERTS First Step Premium Underlayment

Coverage: 100 sq ft

Size: 40 in. x 30 ft

Thickness: 2 mm

✓ 2 mm pad in a 100 sq ft roll, 40 in. by 30 ft✓ Sold by Roberts for floating floors✗ Its delta IIC of 20 is the lowest of these picks

See ratings on Amazon

Roberts rates it IIC 68, STC 67 and delta 20, and says the three layers trap and release moisture vapor while leveling minor subfloor imperfections. It also comes with an overlap film and adhesive strip to join the pieces and lock out moisture.

Its delta is the lowest of the picks, so choose it over Black Jack for the bead layer’s leveling rather than for footstep noise. Roberts’ underlayment product guide sets it beside Black Jack, Super Felt, SoundBarricade and the 6 mm and 12 mm cork, with every rating in one place.

Will a Condo Board Accept Your Underlayment?

Picking a roll is one test, and a condo or HOA board may set another. A board will accept your underlayment only if it meets the board’s own rule, and Laguna Woods Village’s Standard 11A, revised in March 2026, is a detailed example: every new floor needs an underlayment rated delta IIC 20 or higher.

The same standard suggests 12 dB or more for the finish flooring itself. If a neighbor complains, a field test must then show an overall AIIC of 57 or more across the new floor, the new underlayment and the existing floor-ceiling below.

It also puts the cost on whoever the test goes against. If the floor passes, the owner who complained pays for the process, and if it fails, the owner who installed it pays for the testing, the fix and every retest until it complies.

Every pick here lists a delta IIC of 20 or more, so each clears that 20 dB line on paper. The 57 AIIC is the harder target, since it’s a field result for the whole floor, and the lab-to-field gap from earlier can take 3 to 5 dB off.

The standard even draws the build it expects to reach 57. Its cross-section shows 2 to 2 1/2 inches of lightweight concrete over 15 lb felt or 2 mil plastic sheeting, a 1/2-inch plywood layer and 2 x 10 joists at 12 or 16 inches, with the new underlayment and floor on top.

Ask for your building’s rule in writing before you buy. For renters and owners in apartments, Burton Acoustix’s apartment floor guide covers what a lease or building usually allows.

When Is the Underlayment Not the Fix?

Even a pad that passes a board’s rule can disappoint when the problem sits below the subfloor. The underlayment isn’t the fix when the complaint is a deep thump through wood joists or voices through the ceiling, because NRC’s figures put those gains in mass, resilient ceiling support and the joist cavity rather than in a thin pad.

For the cavity, this comparison of joist-cavity insulation sets out what batts add once the ceiling below is resiliently hung. That’s the joist-floor lesson from earlier again: the ceiling side decides how much the rest can do.

If the flooring is still being chosen, carpet sits in a class of its own. NRC’s tables put carpet and underlay at 75 to 85 on both concrete and joists, far above any hardwood build in them.

Even carpet has a limit on joists. NRC adds that a carpeted joist floor can still draw complaints about low-frequency thumps when the floor’s layers are too light.

The Bottom Line

The best soundproof underlayment for hardwood floors is the one rated for your install, with a test floor close to yours. For nailed solid boards that’s FloorMuffler UltraSeal, for floating engineered floors it’s QuietWalk, with Black Jack and First Step as lighter pads, and for glued or floating floors over concrete it’s QEP’s 6 mm cork.

Compare delta IIC between rolls, not headline IICs, and expect the biggest gains on concrete. On wood joists a pad mainly takes the click out of footsteps, while the thud belongs to the ceiling and cavity below.

Frequently Asked Questions

How do you soundproof hardwood floors?

You soundproof hardwood floors by putting a resilient layer under the boards and, on wood joists, by working on the ceiling below as well. NRC Canada’s figures give hardwood on a 6 mm resilient layer an IIC of 45 to 50 on a concrete slab, against 30 to 35 without it, but no gain on a basic joist floor, where a heavier subfloor, a floating plywood layer over mineral fiber board or a resiliently hung ceiling makes the difference. Choose a pad its maker approves for your install method, keep the floor off the walls with a perimeter gap or strip, and lay a moisture barrier over concrete.

What underlay reduces noise the most under hardwood?

On the makers’ own figures, the underlay that reduces impact noise the most among these picks is FloorMuffler UltraSeal, with a delta IIC of up to 25, followed by QuietWalk at 24 under laminate and QEP’s cork at 22. Delta IIC is the fairest comparison because ASTM E2179 measures every covering on a standard concrete test floor. NRC lists shredded or foamed rubber, foamed plastic and cork as the resilient materials commonly used under wood, so the tested result and the install method your floor allows matter more than the material’s name.

What underlayment has the highest IIC rating?

Among these picks, the highest IIC on paper is 74, listed for both QEP’s 6 mm cork and FloorMuffler UltraSeal. QEP’s 74 was measured under ceramic tile on a 6-inch cement slab, and FloorMuffler’s listing gives its 74 as an upper figure without naming the floor. Because IIC rates the whole floor-ceiling assembly, MP Global’s own sheet shows one 3 mm pad scoring anywhere from 55 to 71, so the highest IIC tells you about the test floor as much as the roll. Compare delta IIC instead, or an IIC measured on a floor like yours.

Should you put underlayment under hardwood floors?

Yes, though the right layer depends on the install. Solid boards nailed over a wood subfloor normally go over felt paper, which Stonewood specifies as #15 black felt and Diamond W as 15 lb felt per ASTM D4869, and a sound underlayment goes there only when its maker approves nail-down use. Floating engineered floors need a pad under them, glued floors over concrete can take cork bonded on both faces, and Diamond W requires a moisture barrier over every concrete subfloor. In a condo, the board’s rule may require a rated underlayment as well.

Is cork or foam underlayment better under hardwood?

Neither wins on material alone, because the install method decides first. QEP’s 6 mm cork is the layer for a glued engineered floor over concrete, with a delta IIC of 22 and crack isolation, but it can’t take nails, while Black Jack’s 2.5 mm closed-cell foam is for floating floors only, with a delta of 21. FloorMuffler UltraSeal is the foam that also takes nails and double glue-down. NRC names cork and foamed plastic among the resilient materials commonly used under wood, so pick the one your installation method and moisture conditions allow.