Why stairs are different
On a floor, weight is spread across a whole surface. On a staircase, almost every footfall lands on the nosing — a strip a couple of inches wide. Underlay is what stops that strip from grinding the runner backing against a hard timber edge.
Types of underlay
| Type | Suits stairs? | Notes |
|---|---|---|
| PU foam | Yes, if high density | Common, good value, choose 100kg/m³+ |
| Rubber crumb | Excellent | Firm, heavy, very durable on nosings |
| Sponge rubber | Good | Traditional, resilient, quieter |
| Felt / wool felt | Good with wool runners | Breathable, natural, firm underfoot |
| Very soft thick foam | No | Feels luxurious, crushes on nosings, unsafe |
Thinner and firmer beats thicker and softer
On stairs, aim for around 8–10mm of a dense underlay. Thick, soft underlay makes the tread edge feel unstable and wears through faster.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorHow to cut and fit it
- Cut strips to the runner width less about 1in, so the underlay never shows at the edges.
- Cut each piece long enough to cover the tread and wrap over the nosing.
- Staple along the back of the tread and under the nosing lip.
- Butt pieces at the crease; do not overlap them.
- Keep the underlay clear of the gripper so the runner can hook properly.
Cost
Budget $2–$6 per linear foot, so roughly $45–$130 for a 13-step staircase. Against a runner costing several hundred, spending at the top of that range is the easiest good decision in the project.
Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Frequently asked questions
Do you need underlay under a stair runner?
Yes. It absorbs impact at the nosing where nearly all stair wear happens, makes the runner feel better underfoot and significantly extends its life.
What thickness of underlay is best for stairs?
Around 8–10mm of a dense underlay such as rubber crumb or high-density PU foam. Thicker, softer underlay feels unstable on the tread edge and wears faster.
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Add underlay to my estimate