The rule: the gap equals the carpet thickness
Carpet gripper is nailed down parallel to the wall with a deliberate gap behind it. That gap, usually called the gully, is where the carpet edge is pushed down and tucked so the raw edge is hidden and the tension is held. The correct width is the thickness of the carpet you are fitting: a thin carpet needs a narrow gully or the edge disappears too far and pulls loose, and a thick carpet needs a wider one or the edge sits proud and you can see a ridge along the skirting.
| Carpet type | Typical thickness | Gripper gap | Note |
|---|---|---|---|
| Contract loop / thin cord | 5-6mm | 6mm | Narrow gully, tuck firmly |
| Standard domestic cut pile | 8-10mm | 8mm | The most common setting |
| Thick wool twist | 11-13mm | 10mm | Wider gully or the edge stands proud |
| Saxony / deep pile | 14mm+ | 10-12mm | Check with a scrap before nailing |
| Sisal / natural fibre | 6-8mm | 6-8mm | Stiff backing, tuck with a blunt tool |
The fastest way to set it
Fold a scrap of the actual carpet double and use it as a spacer between the skirting and the gripper as you nail. It sets the gully to the carpet you are fitting rather than to a number you half remember.
Which way round does the gripper go?
The pins lean towards the wall. This is the single most common mistake made by people fitting for the first time, and it is unrecoverable once the carpet is stretched — the pins have to grip against the direction of pull, so if they lean into the room the carpet slowly releases and the edge creeps away from the skirting over the following months. Before you nail a single length, look down the strip and confirm every pin is angled towards the skirting.
- Pins lean towards the wall, always.
- Gripper runs continuously around the perimeter, with short pieces cut for bays and reveals.
- Stop the gripper about 40mm short of a door threshold and use a bar there instead.
- On concrete use masonry pins or adhesive; on timber the pre-set nails are enough.
- Never run gripper across a doorway opening — it is a bare-foot hazard.
The gap on stairs is a different problem
On a staircase there is no perimeter gully in the usual sense. Gripper is fitted in two strips per step: one at the back of the tread and one at the bottom of the riser, forming a V into the crotch where they meet. The spacing that matters here is between those two strips, not between gripper and skirting — around 15-18mm apart, with both sets of pins facing into the crotch so the carpet is gripped from both directions as it is kicked in.
Where a fitted runner is being laid rather than a full-width carpet, the gripper is cut to the runner width less about 20mm so no gripper shows at the edges, and the margin of bare timber on each side stays even all the way down. Getting that width right before you cut anything is what the stair runner width calculator is for, and the stair runner calculator on the home page turns the same measurements into the runner length and the total gripper run.
| Location | Gap or spacing | Pin direction |
|---|---|---|
| Wall / skirting | 6-10mm (carpet thickness) | Towards the wall |
| Tread and riser crotch | 15-18mm between strips | Into the crotch |
| Door threshold | Stop 40mm short, fit a bar | Towards the wall |
| Stair runner edges | Runner width less 20mm | Into the crotch |
| Bay window | Follow the wall line, mitred | Towards the wall |
What goes wrong when the gap is wrong
Too wide and the carpet edge drops too deep into the gully, which pulls tension out of the field and leaves the fitted carpet slightly loose across the room. You see it first as a soft wave a metre off the wall. Too narrow and the edge cannot tuck at all; it stands up as a visible bead along the skirting, catches the vacuum head, and starts to fray within a few months. Both faults are invisible on the day and obvious after a season, which is why fitters set the gully with a scrap rather than by eye.
Underlay stops at the gripper
Butt the underlay up to the inside edge of the gripper, never over it. Underlay lapped onto the pins stops the carpet reaching them and is the usual reason a well-stretched carpet still creeps.
A practical fitting order
- Sweep the subfloor and check for proud nails or loose boards.
- Cut and nail the gripper around the perimeter, gully set with a folded carpet scrap.
- Stop short of doorways and fit the threshold bar.
- Lay the underlay butted to the inside edge of the gripper and tape the joins.
- Rough-cut the carpet with 50-75mm of excess at each wall.
- Hook onto the gripper on one wall, then knee-kick and stretch to the opposite wall.
- Trim the excess with a wall trimmer and tuck the edge into the gully with a bolster.
None of the steps are difficult on their own. The reason professional work looks different is that each one is done to a measurement rather than to a feel — the gully to the carpet thickness, the underlay to the gripper edge, the stretch to a kicker rather than a pull. Set the gap correctly at the start and the rest of the fit has a much easier time holding it.
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
How far should carpet gripper be from the skirting board?
The same distance as the thickness of the carpet, which for most domestic carpets is 8mm. Thin contract carpet takes 6mm, a thick wool twist takes 10mm. Fold a scrap of the carpet double and use it as a spacer while you nail the gripper down.
Why do you leave a gap behind carpet gripper?
The gap is the gully the carpet edge tucks into. It hides the raw edge, keeps the carpet tight against the skirting and stops the edge lifting. Without it the carpet has nowhere to go and stands proud along the wall.
Which way should the gripper pins face?
Towards the wall. The pins have to bite against the direction the carpet is stretched, so pins facing into the room let the carpet release over time. Check the direction along the whole strip before you nail anything.
Should carpet gripper go across a doorway?
No. Stop the gripper roughly 40mm short of the opening and fit a threshold bar instead. Gripper pins in a doorway are exposed to bare feet and there is nothing there to hold the carpet edge down properly.
What gap do you leave for gripper on stairs?
On stairs the measurement that matters is between the tread strip and the riser strip, which should be about 15-18mm apart with both sets of pins pointing into the crotch. There is no skirting gully on a flight in the usual sense.
Does the gap change for underlay thickness?
No. The gully is set by the carpet thickness, not the underlay. The underlay simply butts up to the inside edge of the gripper and stops there — lapping underlay over the pins is one of the most common causes of a carpet that will not hold its stretch.
Can I reuse the old gripper?
Only if it is sound, correctly spaced for the new carpet and the pins are not bent or rusted. Gripper is inexpensive and replacing it takes an hour; reusing tired gripper is the cheapest way to ruin an expensive carpet.
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 the flight with the stair runner calculatorEvery 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.