How to Unlock and Reinstall Vinyl Siding With a Zip Tool

Why this matters

Vinyl siding is the friendliest exterior finish a trade can open. Nothing is glued, nothing is caulked, and every panel hangs on a lock and a row of loose nails. A tech with a zip tool can take a panel off to set an outlet box, a vent hood or a line-set block and hang it back so well nobody can find where it was. The same panel nailed tight on the way back buckles in the first warm week, and the same panel bent hard on a cold morning cracks across its face, and then the shop owes a siding repair with a color nobody stocks anymore.

How a course locks together is in its own card; see related: Vinyl Siding Lock Profiles and How a Course Hangs. This card is the removal and the rehang.

Before you start: height, power, what is behind it

• Ladder. Most siding work beyond the first few courses is ladder work. Set an extension ladder at about 1 ft out for every 4 ft of height to the support point, footed on firm level ground, and keep three points of contact while you work the zip tool; the tool needs two hands at some point, and that is the moment to move to a stable platform rather than lean. Keep any ladder, especially aluminum, well clear of the overhead service drop and the mast where it enters the house.
• What is behind the panel. Vinyl is often installed over an older siding. Asbestos-cement shingles, common on houses through the 1970s, sit under a lot of vinyl, and nailing or cutting into them disturbs them. Look behind the first panel you open before driving any new fastener. If you find cement-board shingles of unknown age, stop and run The Legacy Material Check Before You Disturb a Finish.
• Insects. Wasps nest in the voids behind siding and in the J-channel around windows. Look before you reach in, and work away from an active nest rather than through it.

The lock, drawn

 SIDE VIEW AT ONE COURSE LINE (wall at left)

  wall
   |\
   | \     upper panel face, sloping out
   |[o]\   lower panel nail hem, hidden behind it:
   | |  \  nail centered in slot, head about
   | |   \ 1/32 in proud of the hem
   | +-+  \
   |   |   +  butt: bottom edge of the upper panel
   |   |  /
   |   +-/   lock: the lower panel's lock strip,
   |   |     caught by the upper panel's buttlock,
   |   |     folded back under the butt
   |    \
   |     \   lower panel face, sloping out

  ZIP TOOL: its hook goes up behind the butt and
  catches the buttlock. Pull DOWN and OUT to unhook
  it, then slide the tool sideways along the course.

The one fact to take from the drawing: the nails holding any panel are hidden by the panel above it. So you never remove the panel you want first. You unzip the one above, lift it, and the panel you want is exposed.

The steps

1. Read the temperature and plan the bending. Vinyl loses its flexibility as it gets cold and cracks when bent sharply on a cold day. Check the temperature, and on a cold morning plan the work for the warmest part of the day, or for the side of the house in sun. If you have to work cold, bend panels gently over a wide radius and lift them only as far as you need. If you skip it: the panel above cracks at the lock when you lift it to reach the nails, and that crack is a replacement panel. See related: The Siding Panel That Cracked in January.

2. Unzip the course above the work. Hook the zip tool behind the butt of the panel above the one you need to remove, find the buttlock, pull down and out until it unhooks, and slide the tool along the course. Start at an end lap or at a point where the panel is already loose. Reason: the lock releases progressively along its length, the way a zipper does. If you skip ahead and pry the face, you kink or crack it.

3. Lift the upper panel just enough to reach the nail hem. Prop it up with a short block or have a helper hold it. Do not fold it back flat against the wall above.

4. Pull the nails from the panel you are removing. Use a flat bar with a block under it against the wall, not the siding face. Reason: the panel hangs from those nails, and it comes off only once they are out. Mark each nail location with a pencil on the panel above if you will be nailing into the same studs.

5. Unhook the panel from the course below and slide it out of its end laps. Run the zip tool along this panel's own buttlock to free it from the course below, then slide it sideways out of the overlaps with its neighbors. Reason: end laps are overlapped about 1 in on most systems, and the panel comes out of them by sliding, not by pulling straight out.

6. Protect and store it. Stack removed panels flat, face side up, on a clean surface out of the sun and out of the path. Reason: a long vinyl panel lying on uneven ground in direct sun takes a set, and dark colors can distort if left lying in hot sun against something that traps heat.

7. Do the work, and cut the panel for it with room to move. Where a new block, box or vent goes through the panel, use a mounting block or a split block made for siding and cut the panel to fit around it with a gap of about 1/4 in all round, so the panel slides behind the block's trim ring rather than butting hard against it. Reason: a 12 ft 6 in panel can move a noticeable fraction of an inch between a cold night and a hot afternoon, and it has to slide past the block. Flash the block into the water-resistive barrier as in How to Flash an Exterior Wall Penetration Into the WRB.

8. Rehang the panel loose. Hook its buttlock onto the course below and push up until it locks, slide its ends back into their laps, and nail through the center of each nailing slot into solid wood, at no more than 16 in on center, typically at every stud. Leave the head about 1/32 in off the hem, roughly the thickness of a dime, and drive the nail straight. Reason: the slots let the panel slide; a nail driven tight or off-center pins it. If you skip it: the panel waves or buckles in the first hot spell, or rips around a nail in the first cold one. Hazard: on a ladder, drive nails with the hammer arm in line with your body, not reaching to the side.

9. Zip the course above back on. Hook the zip tool's lip under the buttlock of the upper panel, pull down and push in so the buttlock catches the lock strip of the panel you just hung, and slide along. Push up on the upper panel along its length when you are done to confirm it is locked.

Worked example: an outdoor receptacle in November

An electrician is adding a weatherproof receptacle on a side wall, 18 in above grade, under a window. The box goes into a recessed mounting block made for vinyl siding. The siding is a double 4 in profile, so each panel is 8 in tall, in 12 ft 6 in lengths, which is 150 in. The block lands in the third course up from the starter strip.

Temperature. The electrician arrives at 8 am and the thermometer on the truck reads 34 F. The wall faces south and will be in sun by late morning. The rough-in inside the house goes first, and the siding waits until 11:30 am, when the wall reads 52 F to the touch with an infrared thermometer.

Removal. The fourth course is unzipped from its end lap at the corner along the full 150 in of the panel below it, because every nail in that panel has to come out and each sits behind the fourth course, and propped up 3 in with scrap blocks every few feet so it never bends sharply. The third-course panel's nails come out: one at each stud, nine studs across its 150 in length. A partial unzip over just the block location would have exposed only the nails near it, and the panel would still have been hanging from the rest. It is unhooked from the second course and slid out of its far lap.

Cut and set. The mounting block is fastened through the sheathing into a stud and flashed into the house wrap. The panel is laid on the bench, marked from the block's position, and cut with snips to clear the block by 1/4 in all round. Because the work happens at 52 F, ordinary clearances apply. On a colder install the clearance would be larger, since a panel cut cold has shrunk and will grow: Vinyl Siding Institute guidance widens the gap at channels and openings from 1/4 in to 3/8 in when the panel is installed below 40 F, and the siding maker's instructions govern where they differ.

Rehang. The panel's buttlock is hooked into the second course, its ends slid into the laps, and nine nails driven at the old stud lines, centered in the slots, each head left a dime's thickness proud. The electrician slides the panel side to side by hand: it moves about 1/8 in each way, which is what a loosely hung panel should do. The fourth course is zipped back on and pushed up along its length to confirm the lock.

Result. One panel off and back on, uncut except at the block, no crack in the lifted course, the panel free to slide. The ticket records the temperature at the time of the work, the block used and its flashing, and the course numbers.

How to verify

After rehanging: each rehung panel slides by hand along its length; no nail head is tight against a hem; every lock is engaged, checked by pushing up along the butt; the block's trim ring overlaps the cut edge of the panel all round with clearance behind it; and no crack or stress whitening shows on the course you lifted, which is where a cold-weather crack appears first.

References

• Vinyl Siding Institute, installation guidance (fastening, clearances, cold-weather allowances)
• See related: Vinyl Siding Lock Profiles and How a Course Hangs; The Siding Panel That Cracked in January
• See related: How to Flash an Exterior Wall Penetration Into the WRB
• Siding manufacturer installation instructions for the specific profile