How to Install Tackless Strip and Carpet Cushion

Why this matters

Tackless strip is the only thing holding a stretched carpet at the wall, and a stretched carpet pulls on it with real force for its whole life. A strip set with its pins facing the wrong way, a gully cut too wide, or cushion lapped up onto the pins lets the edge creep, and the customer sees it months later as a wavy edge at the base or a ripple across the room. None of it shows on install day, because the stretch still holds while the carpet is fresh. The strip and cushion are an hour of the job and they decide whether the stretch you put in stays in.

Cushion selection is not here: what the carpet maker requires for thickness and density lives in 'Carpet Cushion Types and the Maker's Cushion Spec', and the carpet warranty rides on it.

Before you start

Start state. Old carpet, cushion, staples and strip are out; the subfloor is swept, fastened and flat, with squeaks and soft spots dealt with under 'Subfloor Assessment + Repair Reference'. On a slab, moisture has been checked under 'Slab Moisture Testing for Flooring' and the cushion chosen to match. You know the installed thickness of the carpet: measure a sample from the backing to the pile tips, lightly compressed with a thumb, because the gully is set from that number.

What is under the old carpet. On a slab or an old wood floor, pulling old strip can lift or crack old resilient tile and the black adhesive under it. Any resilient floor or black adhesive of unknown age is presumed to contain asbestos until tested. If strip removal or new nailing would break, pry up or scrape it, stop that area and go to 'Asbestos in Old Resilient Floors and Adhesive' before anyone continues.

What is in the slab. Do not nail into a slab with in-floor radiant tubing or a post-tensioned slab, which is often marked with a stamp or a sign in the garage. Glue the strip there instead.

Hands and eyes. Tackless pins puncture skin easily: wear gloves when handling and cutting strip, and keep cut-off pieces in a bucket, never loose on the floor. Hardened concrete nails can chip the slab or snap when struck off-center, so wear eye protection whenever nailing into concrete.

Step 1: Pick the strip for the carpet and the floor

Strip comes in widths and pin heights for different carpet backings, and with nails for wood or hardened nails for concrete. Use the pin height the carpet maker's installation instructions name; too short and the backing never seats on the pins, too long and the pins push through the face.

Step 2: Set the strip with the pins leaning toward the wall

Lay the strip with its angled pins pointing toward the wall. Every pin leans the same way around the whole room, including across doorways and in closets.

Why. The carpet is stretched away from the far wall and hooked onto these pins. Pins leaning toward the wall resist the carpet's pull back toward the room; pins leaning the other way let it slide off. A single strip installed backward, usually a short piece in a closet corner, is where a restretch callback starts.

Step 3: Leave a gully slightly less than the carpet's thickness

The gully is the gap between the back edge of the strip and the wall. CRI 105 calls for it to be slightly less than the carpet's thickness. Set it with a gauge block or a scrap of the strip cut to width, held against the baseboard line or the wall.

Why. At trim time the carpet edge is tucked down into the gully with a stair tool. A gully narrower than the carpet's thickness grips the tucked edge so it stays down; one wider than the carpet lets the edge fall in and leaves a dip at the base. Too narrow, and the edge will not tuck at all and stands proud against the base.

  wall
   |
   |####################################
   |##   carpet, stretched toward wall
   |####################################
   |##   \  \  \  \   pins lean to wall
   |##   +----------+------------------
   |##   |  strip   | cushion, butted
   |##   |          | to the strip edge
  =+=====+==========+==================
   |<--->|        subfloor
    gully: the carpet edge is tucked
    down into it; width a little under
    the carpet's thickness

The finished section, once the carpet is stretched and trimmed: backing seated on the pins, edge tucked into the gully, cushion stopping at the strip.

Step 4: Fasten it so nothing moves

On wood: drive the strip's own nails flush, and add one within about 2 in of each cut end so short pieces cannot spin under the stretcher. On concrete: use the hardened-nail strip, or glue it with the adhesive the strip maker lists where nailing is ruled out. Butt strip ends tightly; around a curve or a column, cut short lengths and follow the shape rather than leaving a gap.

Across doorways: where carpet meets another floor, the strip runs across the opening set back for the transition piece, per 'Transition Profiles and the Accessible Level Change'. Where carpet continues into the next room or a closet, there is no strip in the opening.

Step 5: Lay the cushion and trim it to the strip

Roll the cushion out with the side the maker marks as up facing up; many have a film or a smoother face for the carpet to slide on during stretching. Trim it so it butts against the inside edge of the strip, not on top of it and not short of it.

Why exactly to the edge. Cushion lapped onto the strip lifts the carpet off the pins and the edge never grips. Cushion stopped short leaves a trough along the wall that the carpet sags into and shows as a line along the base.

Step 6: Seam the cushion, then fasten it

Butt cushion pieces tight, with no gap and no overlap. Tape the seam with the cushion maker's seam tape. On wood, staple both sides of every seam and along the perimeter about every 6 in, or at the spacing the maker gives, with staples set flush. On concrete, glue the perimeter and the seams with the adhesive the cushion maker names.

Keep cushion seams away from carpet seams. A cushion seam directly under a carpet seam doubles the weak line: the carpet seam has a slight ridge of tape and adhesive, the cushion seam a slight dip, and traffic works the two together until the carpet seam shows. The shop default is at least 6 in apart, and where the room allows, cushion runs at right angles to the carpet seams so they cross rather than parallel.

Worked example: a bedroom with a closet

A second-floor bedroom on an OSB subfloor measures 11 ft 6 in by 14 ft, with a 3 ft door to a hardwood hall in one short wall and a closet 6 ft wide and 2 ft deep in the opposite short wall, flush with the east side wall. The carpet is a cut pile that measures 7/16 in thick under light thumb pressure, and it comes on a 12 ft roll, so one piece covers the 11 ft 6 in width with no carpet seam. The cushion the carpet maker's spec allows comes 6 ft wide.

Strip quantity:

At 4 ft a length, 55 ft is 13-3/4 lengths, so 14, and the crew carries a 15th because the closet uses four short cuts. The door gets strip across the opening, set back for the carpet-to-hardwood transition.

Gully: slightly less than 7/16 in, so a 3/8 in gauge block, checked at every corner.

Cushion layout: two pieces running the 14 ft length. Piece 1, a full 6 ft wide, goes along the east wall and runs 16 ft, through the room and on into the closet; piece 2, trimmed to 5 ft 6 in, fills the west side for 14 ft. That is 30 linear ft of 6 ft cushion, 180 sq ft bought against 173 sq ft of floor (161 sq ft of room plus 12 sq ft of closet); the 7 sq ft difference is the 6 in trimmed off piece 2 along its 14 ft length. The one cushion seam runs 14 ft lengthwise, 6 ft off the east wall. Because the carpet has no seam in this room, nothing has to cross it; the next room, where a carpet seam falls 12 ft off a wall, gets its cushion run crosswise so the two seams meet at right angles.

One thing went wrong. At the closet's back corner, the installer's short end piece went down with its pins facing the room. It was caught in the check walk-around below, before the carpet was unrolled, because the check is done by eye, piece by piece, rather than by assuming a pattern held.

What changes the answer

• A basement slab. Strip is glued or hardened-nailed, the cushion is glued at seams and perimeter rather than stapled, and the cushion type follows the slab's moisture results. A cushion with a built-in moisture barrier is a cushion choice, not a substitute for testing.
• A low-profile loop or a dense commercial-style carpet. The carpet is thinner and stiffer, so the gully closes up with it, and many makers call for a thinner, firmer cushion. Getting the gully right matters more here, because a stiff backing that will not tuck stands up against the base in plain view.
• Stairs. Strip placement on treads and risers is a different geometry; see 'How to Install Carpet on Stairs'.

How to check you got it right

Before the carpet is unrolled, walk the perimeter with the plan:

• Pins: every length, including each short closet and corner piece, leans toward the wall.
• Gully: the gauge block drops in at each corner and at mid-wall with no slop and no forcing.
• Fastening: no strip moves when pushed toward the room with a thumb; nails flush; a nail near every cut end.
• Cushion: butted to the strip edge everywhere, never on it; seams tight with tape across them and staples or adhesive along both sides; no wrinkles or lumps when you walk it in socks; staples flush so none read through the carpet.
• Seam separation: no cushion seam within 6 in of a planned carpet seam.

A strip that passes all five holds the stretch the next card puts into it. One that fails any of them tends to come back as 'How to Pull Back Carpet at a Wall and Restretch It'.

References

• CRI 105, the Carpet and Rug Institute's installation standard for residential carpet, as referenced by the carpet maker's warranty; check the current edition
• The carpet and cushion makers' installation instructions, which govern strip, cushion, staple spacing and adhesive
• See related: Carpet Cushion Types and the Maker's Cushion Spec; Asbestos in Old Resilient Floors and Adhesive; Transition Profiles and the Accessible Level Change
• See related: Subfloor Assessment + Repair Reference; Slab Moisture Testing for Flooring; How to Pull Back Carpet at a Wall and Restretch It