How to Install Vinyl Siding

Two things worth knowing before you buy anything. First, these are not just tips. The residential code says vinyl siding shall be installed in accordance with the manufacturer's instructions, which makes the nailing rules below enforceable at an inspection, not merely advisable. Second, the code sets its own floor underneath them, and one of those numbers is the one homeowners most often get wrong.

Before you pull a single board: how old is the house?

This page used to skip straight to the wall. That was a mistake, and it is the kind that does not show up for thirty years.

Houses finished before 1978 should be treated as having lead in the old paint until a test says otherwise. And if the old siding itself is a hard, brittle, cementy shingle, it could be asbestos-cement, and looking at it will not tell you. EPA is unambiguous: the only way to be sure whether a material contains asbestos is to have it tested by a qualified laboratory. A build year clears nothing. A lab does.

Now the part nobody tells you, and it is the reason this section exists. EPA's lead rule, the one that forces contractors into containment and certified crews, applies to renovations performed for compensation. You are not paying yourself, so it does not bind you. The federal asbestos rule excludes residential buildings with four or fewer dwelling units, so it does not bind you either. OSHA covers employers with employees, and you are neither. EPA says it out loud: federal law does not require people who remove asbestos-containing materials in detached single-family homes to be trained or accredited. Every federal rule written to keep this dust out of a child's lungs steps around the homeowner doing it himself.

The dust does not know that. So do it in this order: find the build year, and if it is pre-1978 or the old siding is cementitious, get it tested before you touch it. Then call your state or regional air agency, because several go far past the federal floor, and a few require a certified survey even from you. And know that the cheapest option is sometimes also the safest one: leaving sound old siding in place and going over it avoids the whole problem, which is the rare case where doing less is doing better. If it does have to come off, never break, cut, sand, or torch it, wet it down first, keep the pieces whole, and never dry-sweep the debris.

Is vinyl siding difficult to install yourself?

For a single-story house with simple walls, a careful first-timer can do it. Clicking panels together and cutting them is the easy part. The parts that take real attention are getting the starter strip dead level, flashing the windows and rooflines so water sheds outward, and fastening every panel loose enough to move.

Where it stops being a weekend project is height and water. Anything needing scaffolding above the first floor, a wall with rot under the old siding, or a tricky roof-to-wall junction is where mistakes get expensive and, up a ladder, dangerous.

The rule that makes or breaks the job: do not nail tight

VSI leads its fastening section with this, and so will I. Drive each nail until the head is close to the panel, then stop, leaving about the thickness of a dime, roughly 1/32 inch, between the head and the nailing strip. Some manufacturers publish more latitude than that; CertainTeed says 1/16 to 1/8 inch. The panel should hang from its nails, not be pinned by them.

• Leave a dime's thickness under every nail head. Tight nails are the number one cause of a wavy, buckled wall.
• Nail in the center of each slot, not the end, so the panel can slide both ways as it moves.
• Drive nails straight and level, not at an angle, or the panel distorts.
• Space fasteners no more than 16 inches apart on horizontal panels, every 12 inches on vertical panels, and every 8 to 12 inches on accessories and trim. Start in the center of a panel and work out toward the ends.
• Never face-nail through the front of a panel, with one exception the manual names outright: the last panel at a gable peak has to be fastened with a trim nail, and VSI says so.

Want to check your own work? After nailing a course, grab the bottom edge and try to slide it sideways. The test is pass or fail, not a measurement: VSI says installed panels must move freely from side to side. If it is locked solid, your nails are too tight, and it is worth pulling them now rather than watching the wall ripple all summer. Do not chase a specific distance of travel and keep backing nails out to get it. Loose enough to slide is the whole standard, and over-loosening a fastener is its own failure, the one that shows up in a windstorm.

The fastener spec, which is where the code actually bites

This is the number to get right, and the one we had wrong on this page until somebody finally opened the code and looked. The fastener must penetrate the sheathing and framing a total of at least 1-1/4 inches. Not 3/4 of an inch. That older figure comes from a superseded standard, and VSI now flags it as out of date in its own code guide. Use a nail with a head at least 5/16 inch across and a 1/8 inch shank, so it cannot pull through the slot. Roofing nails work well because of the wide head. If you use screws instead, VSI wants a #8 truss-head or pan-head, and the same 1-1/4 inch penetration.

It matters more than it sounds. A short fastener does not show up on install day, or on a still afternoon, or the first year. It shows up when a storm gets under the panel, and by then the wall is off.

Tools, fasteners, and the one that can hurt you

• Aviation snips and a utility knife for cutting
• A snap-lock punch, which raises tabs on a cut top edge so the finish course locks into utility trim
• A nail-slot punch, to extend or add a nailing slot in a cut panel
• An unlocking (zip) tool for unhooking a panel from the course below
• A 4 foot level, a chalk line, a tape, and a framing square
• Corrosion-resistant fasteners: aluminum, galvanized steel, or stainless. Aluminum trim needs aluminum or stainless specifically.

And the circular saw, which comes with a real warning we used to leave off. VSI does tell you to install a fine-tooth plywood blade backward on the saw, which gives a smoother, cleaner cut, especially in cold weather. But it attaches conditions, and here they are in its own words: cut slowly, and do not attempt to cut materials other than vinyl with a reversed direction saw blade, because using a backwards blade on any other material could be unsafe. Wear eye protection. VSI recommends it for all cutting and nailing, and this is a page that just told you to run a blade the wrong way round.

Start with the wall, not the siding

Before a panel goes up, the wall has to be sound and flat. VSI is direct about it: a flat, level wall surface is necessary, you should check all walls for evenness and install furring strips where needed, and you must not install vinyl siding over rotting wood. A wavy wall telegraphs through the panels forever, and no amount of careful nailing hides it.

Then the whole wall gets house wrap, the water-resistive barrier, laid over the sheathing before any trim or siding goes up. House wrap is not a nice-to-have, it is code: the residential code wants that barrier on the studs or the sheathing of every exterior wall. The wrap is your real waterproofing. The vinyl over it is a rain screen that takes the beating; water that slips past it rides down the wrap and back out.

Flashing comes next, and the golden rule is that every layer laps over the one below it like shingles, so water always travels down and out, never in. At windows and doors, tuck flashing under the wrap at the top and lap it over the siding below. Where a roof edge dies into a sidewall, you need kickout flashing, the angled diverter that throws roof runoff into the gutter instead of behind your panels. Plan it before you side over it, and if you are hiring any part of this out, know that whose job the kickout is turns out to be a real argument.

The starter strip sets the whole wall

Every course follows the starter strip, so if the starter is off, the wall leans a little more with every row until it is visibly crooked at the top. Be fussy here.

Find the lowest corner of the wall. Measure up a distance a quarter inch less than the width of your starter strip, mark it, and snap a level chalk line around the house. Nail the strip along the line every 8 to 12 inches, and leave about a quarter inch between the ends of neighboring strips so they can expand. Keep the starter back from any head flashing so you do not block the weep holes that let the wall drain.

Corner posts, then J-channel

Install the corner posts next, then run J-channel around windows, doors, and rooflines. A corner post hangs from two nails, one at the top of the upper slot on each side, and every nail below floats loose in the center of its slot so the post can grow downward without buckling. Leave about a quarter inch between the top of the post and the eave, and run the post about 3/4 inch below the starter strip.

Two things people get wrong. Drill weep holes at least 3/16 inch across, no more than 24 inches apart, in the bottom J-channel, so trapped water can escape. And do not caulk the channels shut. It is tempting to seal every joint, but the open channels and weep holes are the drainage path. Caulk them and you trap water in the wall, which is the exact opposite of the point.

Hang the first course, then work up

Lock the bottom edge of the first panel into the starter strip until it snaps, then nail the top flange, loose and centered, starting in the middle and working out. Do not pull up hard on a panel while you nail it. That power-lifting cracks the nailing flange. Click it in and let it rest.

Leave room at the ends. Where a panel meets a corner post or J-channel, leave a 1/4 inch gap for expansion, or 3/8 inch if you are working below 40 degrees, because the panel is at its shortest in the cold and will grow. Overlap panel ends by about an inch, and point the laps away from the front door and the way you walk up, so the seams are hard to see. Stagger the seams so no two courses line up unless they are separated by at least three courses, and avoid starting or ending a course with a piece shorter than 24 inches. Check horizontal alignment every fifth or sixth course, and against the adjoining walls, before the error has anywhere to hide.

Faucets, lights, and anything you hang on the wall

This is the step that catches people on wall one, and it follows straight from the loose-nail rule. Anything you fasten through vinyl has to let the vinyl move behind it. For a hose bib, a railing bracket, or a light, use a split or hinged trim ring made for the job. Where you must run a fastener through a panel, drill the hole a quarter inch larger than the fastener's shank so the panel can slide around it. Same for shutters: oversize the hole, and never draw the shutter down tight against the siding. Pin a panel with one screw and the whole course will buckle, and you will spend a weekend hunting for a cause that is a shutter.

Finishing the top course

The last course under the eave usually has to be cut down in width, which removes its nailing strip. That is what the snap-lock punch is for: run it along the cut edge to raise tabs every 6 inches, then lock those tabs into a length of utility trim nailed up under the soffit. The panel snaps in and holds with no face nail showing. Measure the gap in several places first, since an eave line is rarely even.

Common vinyl siding mistakes

• Ripping into pre-1978 siding without testing it for lead or asbestos. The only mistake on this list you cannot fix by redoing the wall.
• Nailing tight, so the wall buckles and waves the first hot afternoon
• Fastening short. The code minimum is 1-1/4 inches of total penetration, and a short nail only fails in a storm.
• A starter strip that is not level, which throws off every course above it
• No expansion gap at the corner posts and channels, so panels warp in the heat
• Caulking the J-channels and weep holes shut, trapping water in the wall
• Reusing torn old house wrap, or skipping the wrap, and counting on vinyl alone to keep water out
• Screwing a shutter or a light tight to the panel, which pins the course and buckles it

When to hand it to a pro

• Old siding that tests positive for lead or asbestos. That is an abatement job before it is a siding job.
• Two-story walls or anything needing scaffolding, where a fall is the real risk, not a crooked panel
• Soft or rotted sheathing found after the old siding comes off, which is a repair job before it is a siding job
• Complicated rooflines, dormers, and chimney tie-ins, where one missed flashing lap leaks for years before it shows