Guide · For the trade
Carpet pad for stairs: the thickness and density to specify
The right carpet pad for stairs is thin and dense: 1/4 to 3/8 inch of felt, slab rubber or a 32 ounce felt-and-rubber combination, not the 7/16 inch 8 pound rebond that goes under a bedroom carpet. A thick, soft pad lets the carpet flex over the nosing, which wears the fiber, loosens the tack and makes the step feel unstable underfoot. Every stair runner and every wall-to-wall stair installation gets a pad; the choice is only which one.
This guide is for the designer writing the stair spec or checking an installer's quote: why stairs take a different pad from the rooms, the pad types and their numbers, how the pad is cut and placed under a runner, what the pad does to riser heights and code, and the questions clients ask. It is a sub-page of our stair runner collection, and it pairs with the wool stair runner guide on fiber and construction.
Do stairs need padding under the carpet?
Yes, on every installation that is stretched in rather than glued down. The pad does three jobs on a stair that it does not do in a room. It cushions the fiber at the nosing, where the carpet bends over a hard edge and would otherwise wear through from the back. It quiets the stair, which is the first thing a client notices in a house with a wood stair and a second floor of bedrooms. And it gives the tackless strip something to stretch the carpet over, so the runner stays tight. The one stair that takes no pad is a glued-down commercial installation, usually a low loop or a carpet tile.
Why the room pad is wrong on the stair
Standard residential pad is 7/16 inch 8 pound bonded urethane, called rebond, and it is right under a cut pile carpet in a bedroom. On a stair it is too thick and too soft. The carpet sinks into it on the tread and bends sharply over the nosing, so the backing cracks and the pile opens at the bend, the foot rocks on the soft edge, and the extra 7/16 inch at the top and bottom step changes the riser height. Mills specify a thinner, denser pad under Berber, loop, Wilton and any stair installation, and the warranty on a woven wool runner usually depends on it.
What is the best type of carpet padding for stairs?
Four types work, and the choice depends on the carpet and the floor under it.
| Pad | Thickness | Density or weight | Specify it under |
|---|---|---|---|
| Synthetic felt (fiber pad) | 1/4 to 3/8 in | 32 to 40 oz per sq yd | Wool Wilton, wool loop, Berber and most stair runners; the default stair pad |
| Felt and rubber combination | 1/4 in | 32 oz felt with a natural rubber face | Runners on finished wood or stone stairs, flatweaves, anything that must not shift or mark the floor |
| Slab rubber | 1/4 to 3/8 in | 19 to 22 lb per cu ft | Wall-to-wall stairs in a high-traffic house, hand-loomed wool, a client who wants the firmest step |
| High-density rebond | 1/4 to 3/8 in | 8 to 10 lb per cu ft | Acceptable under a dense cut pile on a wall-to-wall stair when the budget is tight; never 7/16 in on a stair |
Waffle rubber, the old soft sponge pad with the grid pattern, does not belong on a stair at any thickness; it compresses to nothing and crumbles within a decade. Memory foam is the same story. If an installer quotes a stair with the same pad as the rooms, ask which pad and which thickness.
What thickness of carpet pad for stairs?
Between 1/4 and 3/8 inch. Use 1/4 inch under a flatweave, a thin Wilton or a sisal runner, where a thicker pad would let the edges curl and show the pad from the side. Use 3/8 inch under a wool loop or a cut pile with a pile height of 3/8 inch or more, where the extra cushion keeps the nosing from feeling hard without making the step soft. For an accessible route the ADA limits pile height to 1/2 inch over a firm pad, and 1/4 inch felt meets it.
How the pad is cut and placed under a stair runner
This is what to tell the installer, and what to check on the site visit.
- Cut the pad 2 inches narrower than the runner, so it stops about 1 inch inside each edge. The runner then lies flat on the tread at the sides and the pad never shows.
- Cut a separate piece for each tread. The pad runs from the tackless strip at the back of the tread to the front edge and, on a waterfall install, wraps over the nosing and stops on the riser; on a Hollywood install it covers the tread and the nosing only.
- Staple or tack each piece so it cannot creep. On finished wood, rubber face down and the fewest staples, at the back of the tread.
- On a landing, pad the full field with the same pad as the treads, seams taped, and run the tackless strip around the perimeter.
- On a wall-to-wall stair, cover the tread and riser both; the pad on the riser is thinner, usually 1/4 inch, so the carpet pulls tight under the nosing.
Most installers carry a 32 ounce felt and a 1/4 inch felt-and-rubber pad for stairs; if the stair spec calls for slab rubber it goes on the order with the carpet, and we can supply it with the runner.
What is the 25 rule for stairs, and why the pad matters to it
The 25 rule is a stair-geometry rule, not a pad rule, but the pad changes the numbers. Two risers plus one tread should add up to 24 to 25 inches, which puts a 7 inch riser with an 11 inch tread, or a 7.5 inch riser with a 10 inch tread, in the comfortable range. The International Residential Code limits the difference between the tallest and shortest riser in a flight to 3/8 inch. Carpet and pad add their thickness to every tread except the floor at the bottom and the landing at the top, so a 1/2 inch carpet over a 7/16 inch pad adds nearly 1 inch at the first step and takes it away at the last. On an existing stair, a 1/4 inch pad under a 3/8 inch runner keeps the change inside the 3/8 inch limit, and a 7/16 inch rebond pad does not.
Pad for a stair runner over wood, stone and tile
On a finished wood stair the pad also protects the finish: specify a felt-and-rubber combination with natural rubber, not a synthetic rubber that can yellow a finish over years. On a stone or tile stair the carpet cannot be tacked, so the runner is held by stair rods or a low-tack adhesive at the back of each tread over a 1/4 inch rubber pad that grips the stone. On an outdoor stair there is no pad; a polypropylene runner is glued direct.
Questions designers ask
What is the best carpet pad for stairs?
A 32 ounce synthetic felt at 1/4 to 3/8 inch is the default under a wool Wilton, loop or stair runner. On finished wood, a 1/4 inch felt-and-rubber combination. Under a dense cut pile on a wall-to-wall stair in a busy house, 3/8 inch slab rubber.
Do stairs need padding under the carpet?
Yes, on every stretched-in installation. The pad protects the fiber at the nosing, quiets the stair and lets the installer stretch the carpet tight. Only glued-down commercial stairs go without.
What thickness carpet pad for stairs?
Between 1/4 and 3/8 inch. Thinner under flatweaves, Wiltons and sisal; 3/8 inch under loops and cut piles with a pile of 3/8 inch or more. Never the 7/16 inch rebond used in the rooms.
What is the 25 rule for stairs?
Two risers plus one tread should total 24 to 25 inches, and risers in a flight may not vary by more than 3/8 inch. Thick carpet and pad eat into that tolerance at the top and bottom step, which is why a stair pad stays thin.
Does a stair runner need a different pad from the hall runner?
No. Use the same 1/4 to 3/8 inch felt or felt-and-rubber under the hall runner so the transition at the top of the stair is level.
Can the pad show at the edges of a stair runner?
Not if it is cut 2 inches narrower than the runner. If a client sees pad at the edge, the installer cut it full width; it is a half-day fix.
Browse: stair runners · wool stair runners · stair runner installation · stairs and hallways · wool broadloom