The short answer
1/2in (12mm) narrow-crown staples, 18–20 gauge
That covers most runner-and-underlay combinations on softwood or engineered treads. Go to 9/16in or 5/8in for thick runners or where you are also fixing underlay in the same pass.
Choosing by build-up
| Situation | Staple length |
|---|---|
| Thin flatweave runner, no underlay | 3/8in (10mm) |
| Standard runner + underlay | 1/2in (12mm) |
| Thick wool runner + underlay | 9/16in–5/8in (14–16mm) |
| Runner over existing low-pile carpet | 5/8in–3/4in (16–19mm) |
Crown width and gauge
Use narrow-crown staples, around 1/4in. A wide crown grips more but is visible in the pile and can crush a low-pile runner. 18 or 20 gauge is the sweet spot — fine enough to disappear, strong enough to hold.
Spacing
- Every 3–4in across the crease at the back of each tread.
- Two extra staples just under the nosing on each side of the runner.
- Closer spacing — every 2in — on the top and bottom steps, which take the most stress.
- Angle staples slightly into the timber rather than straight down.
Manual, electric or pneumatic?
| Stapler | Verdict |
|---|---|
| Heavy-duty manual | Fine for softwood; hard work over 13 steps |
| Electric | Best value for DIY; consistent depth |
| Pneumatic | What fitters use; fastest and most controlled |
On old hardwood treads, test on an off-cut first. If staples sit proud, the gun lacks power for that timber and you will need pneumatic or a shorter, finer staple.
Staple gauge explained
| Gauge | Wire thickness | Best for |
|---|---|---|
| 16 gauge | Thickest, strongest | Heavy jute or wool runners, older hardwood |
| 18 gauge | Standard | Most runner and underlay combinations |
| 20 gauge | Finer | Thin flatweaves, delicate fibres, softer pine |
Crown width matters too
Narrow-crown staples (about 1/4in / 6mm) sit inconspicuously in the crease and are the standard choice for runners. Wide-crown staples spread load over a larger area and are sometimes preferred for underlay alone, but they are more visible if they ever end up slightly proud of a light-coloured fibre.
Signs you have the wrong staple size
- Staples sitting proud of the pile — legs too short or gun underpowered for the timber.
- Staples splitting the tread edge — legs too long for the wood thickness at that point.
- Runner pulling loose within weeks — gauge too fine for the fibre weight.
- Visible dimples in the pile surface — crown too wide for a thin runner.
Always test on an offcut first
Five minutes testing staple size and gun pressure on a spare piece of runner and a scrap of the actual tread timber saves a flight full of redone joints later.
Staples vs alternative fixings
| Fixing method | Where it is used | Verdict |
|---|---|---|
| Narrow-crown staples | Crease at back of tread, nosing edges | Standard, strongest, cheapest per fixing |
| Carpet tacks | Historic method, still used on very old timber | Slower to place, largely superseded by staples |
| Construction adhesive | Occasionally on concrete or tile stairs | Permanent, hard to reposition, not for timber treads |
| Double-sided tape | Temporary or rental fixes only | Not secure enough for daily stair traffic |
How many staples a typical flight actually uses
A standard 13-step straight flight with underlay typically uses 250-400 staples once you count the crease line, the nosing edges and the tighter spacing at the top and bottom steps. A box of 5,000 narrow-crown staples, which costs roughly $8-15 / £6-12, comfortably covers two to three staircases of that size with spares left for future repairs — buy one box rather than trying to calculate the exact count and running short mid-flight.
Staple depth and setting the gun correctly
Most electric and pneumatic staple guns have a depth or pressure adjustment. Set it so the staple crown sits flush with the pile surface, not proud and not buried so deep it crushes the fibre around it. Test on an offcut of the actual runner over a scrap of similar-age timber before starting on the real staircase, and re-check the setting if you move from a softwood tread to a harder engineered or hardwood one partway up the flight, since the same setting rarely suits both.
Repairing a staple that has pulled or split
- Remove the failed staple fully with pliers rather than stapling over the top of it.
- Check whether the timber has split — if so, move the new staple position slightly rather than reusing the same hole.
- Fill a visible split with wood filler and let it cure before restapling nearby.
- Re-tension the runner over the nosing before placing the replacement staple, since a loose staple is almost always a symptom of a loose runner, not a fixing fault on its own.
Staple choice by fibre type
| Fibre | Recommended staple | Reason |
|---|---|---|
| Wool, cut or loop pile | 18 gauge, 1/2in, narrow crown | Balances hold with minimal pile disturbance |
| Sisal / jute / seagrass | 16-18 gauge, 1/2in-9/16in | Coarser weave needs slightly more holding power |
| Polypropylene / nylon flatweave | 18-20 gauge, 3/8in-1/2in | Thinner backing needs less penetration |
| Thick shag or plush synthetic | 16 gauge, 9/16in-5/8in | Extra length needed to reach through deep pile and backing |
Matching staple length to build-up thickness
The rule of thumb is that the staple should penetrate the substrate by at least twice the combined thickness of what it is passing through. A 9mm underlay plus a 9mm carpet backing needs a crown staple around 14 to 16mm long to hold reliably in softwood; the same build-up in oak takes a shorter, thicker staple because hardwood grips far more per millimetre. Too long and you risk hitting a nail plate or splitting the riser; too short and the staple works loose within months as the carpet flexes.
| Substrate | Build-up | Staple length | Gauge/crown |
|---|---|---|---|
| Softwood tread | Pad + wool backing | 14-16mm | 20-22ga, 10mm crown |
| Softwood tread | Pad + heavy jute back | 16-18mm | 20ga, 10mm crown |
| Oak/hardwood | Pad + any backing | 10-14mm | 18-20ga, narrow crown |
| MDF/ply riser | Carpet only | 10-12mm | 22ga, 10mm crown |
Spacing and placement
Staples belong in the tread-riser junction and along the back of the tread, where they are hidden by the carpet's own tension and invisible from above. Space them at 50 to 75mm centres across the width, closing to 25mm at the outer 50mm of each side where the runner is most likely to lift. Never staple through the face of the pile on a nosing: it crushes the tuft, and on a cut pile it leaves a permanent dimple that catches light from the landing.
Test five staples before you commit
Fire five staples into an offcut of the actual riser material with the actual build-up in place. If they sit slightly proud, go one gauge thicker or one length shorter rather than hammering them home — a hammered staple has usually already broken the backing yarns around it.
Hand tacker, electric or pneumatic
A hammer tacker is fast and cheap but has almost no depth control, which makes it a poor choice on hardwood. A good manual or electric staple gun with adjustable drive gives consistent depth and is the sensible DIY option. Pneumatic guns are what fitters use on volume work; they are precise and tireless but unforgiving on thin risers. Whichever you use, keep the nose square to the surface — a staple driven at an angle holds at roughly half the pull-out strength of one driven flat.
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.
Still deciding on material, width or pattern? Our hub on stair runners compares weaves, widths, backings and fitting styles side by side, then hands the numbers straight to the calculator.
Frequently asked questions
What size staples for a stair runner?
1/2in (12mm) narrow-crown staples in 18–20 gauge suit most runner and underlay combinations. Use 3/8in for thin runners with no underlay and up to 5/8in for thick wool runners.
How far apart should stair runner staples be?
Every 3–4in along the crease at the back of each tread, plus a couple under the nosing on each side. Tighten to every 2in on the top and bottom steps.
Can I use a regular office or DIY staple gun?
A light-duty stapler will struggle with underlay and hardwood treads. Use a heavy-duty manual, electric or pneumatic carpet stapler designed for at least 1/2in narrow-crown staples.
How many staples does a typical staircase need?
A 13-step flight with underlay typically needs 250-400 staples once the crease, nosing edges and tighter top/bottom spacing are counted. A standard box of 5,000 covers two to three staircases with spares for repairs.
What happens if the staples are too short?
They fail to grip through the underlay and runner backing into solid timber, so the runner works loose within weeks or months, particularly at the heavily flexed nosing edge.
What is the best staple size for a stair runner?
14-16mm crown staples in softwood with a pad and standard backing, dropping to 10-14mm in oak or other hardwood. Test five in an offcut of the real riser before you start.
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.
Plan your runner installEvery guide is written from hands-on measuring and fitting experience, checked against the calculator’s own maths, and re-reviewed whenever prices or methods change. Read our editorial standards.