Vinyl siding under the 2021 International Residential Code (IRC) must be certified to ASTM D3679 and installed per the manufacturer's instructions. The code defaults are a 0.120 inch shank nail with a 0.313 inch head, 1-1/4 inches of total penetration, and fasteners no more than 16 inches apart on horizontal siding (Section R703.11).
Vinyl siding is a thin, lapped plastic cladding that hangs from nailing slots rather than being pinned tight, so it can move with temperature. The code does not give a full installation method. It sets a baseline for labeling, fasteners and wind resistance, and then defers to the manufacturer for almost everything else.
Key facts
- Vinyl siding must be certified and labeled as conforming to ASTM D3679 by an approved quality control agency (2021 IRC Section R703.11).
- Unless the manufacturer specifies otherwise, vinyl siding fasteners are a 0.120 inch shank nail with a 0.313 inch head, or a 16-gage staple with a 3/8 inch to 1/2 inch crown (2021 IRC Section R703.11.1.1).
- Total fastener penetration into sheathing, furring framing or other nailable substrate must be at least 1-1/4 inches unless the manufacturer's instructions and a test report say otherwise (2021 IRC Section R703.11.1.2).
- Maximum fastener spacing is 16 inches for horizontal siding and 12 inches horizontally and vertically for vertical siding (2021 IRC Section R703.11.1.3).
- Insulated vinyl siding must be certified to ASTM D7793 and installed per the manufacturer's instructions (2021 IRC Section R703.13).
- At least one layer of water-resistive barrier must be applied over studs or sheathing on all exterior walls (2021 IRC Section R703.2).
What does the IRC require for vinyl siding installation?
The 2021 IRC requires vinyl siding, soffit and accessories to be installed in accordance with the manufacturer's instructions (Section R703.11.1), and it adds fastener, penetration, spacing and foam sheathing rules on top.
Table R703.3(1) lists a nominal thickness of 0.035 inch for vinyl siding and notes that thicknesses in that table are based on a maximum stud spacing of 16 inches on center (Section R703.3). Greater stud spacing is allowed only where the siding manufacturer's instructions and a test report or other documentation support it. For how the wall behind the siding is laid out, see stud spacing.
The adopted code edition and your local amendments govern, and the instructions in the siding carton come first.
What goes on the wall before the siding?
At least one layer of water-resistive barrier goes over the studs or sheathing, continuous to the top of the wall, and it must stop correctly at penetrations and appendages (2021 IRC Section R703.2).
Accepted materials include No. 15 felt to ASTM D226 Type 1, ASTM E2556 Type 1 or 2 barriers, and other approved materials used per their manufacturer's instructions. No. 15 asphalt felt and E2556 barriers are applied horizontally with the upper layer lapped over the lower by at least 2 inches, and joints lapped at least 6 inches.
Flashing is required at openings; follow your local code for the details. The structural layer under the barrier is covered in wall sheathing.
What nails or staples hold vinyl siding?
Unless the manufacturer specifies otherwise, the 2021 IRC calls for a nail with a 0.120 inch shank diameter and a 0.313 inch head, or a 16-gage staple with a 3/8 inch to 1/2 inch crown (Section R703.11.1.1).
Section R703.3.3 adds general rules for all exterior wall coverings: fasteners must be aluminum, galvanized, stainless steel or rust-preventative coated, and nails and staples must comply with ASTM F1667. Staples must have a crown width of at least 7/16 inch and be made of at least 16-gage wire. This article covers wood framing only.
How deep should vinyl siding nails penetrate?
Fasteners go into building framing with a total penetration of at least 1-1/4 inches into sheathing, furring framing or other nailable substrate, unless the manufacturer says otherwise (2021 IRC Section R703.11.1.2).
There is one alternative. Where the manufacturer's instructions specify it and a test report supports it, fasteners may penetrate into or fully through nailable sheathing of the minimum thickness stated in the instructions or report, without reaching the framing. If a fastener goes fully through the sheathing, its end must extend at least 1/4 inch beyond the opposite face.
Section R703.3.4 repeats the 1-1/4 inch figure over wood or wood structural panel sheathing, measured into sheathing and framing combined. Over fiberboard or gypsum sheathing, fasteners must penetrate at least 1-1/4 inches into the framing itself.
How far apart should vinyl siding nails be spaced?
Fastener spacing is no more than 16 inches for horizontal siding, and no more than 12 inches both horizontally and vertically for vertical siding, unless the manufacturer specifies otherwise (2021 IRC Section R703.11.1.3).
2021 IRC Section R703.11.1.3, maximum fastener spacing for vinyl siding unless the manufacturer's instructions specify otherwise.
| Siding orientation | Maximum spacing between fasteners |
|---|---|
| Horizontal | 16 inches |
| Vertical | 12 inches horizontally and 12 inches vertically |
Greater spacing is permitted where the manufacturer's instructions specify it and a test report supports it.
What about nail slot gaps and expansion room?
The code does not give numbers for how far to leave nail heads off the siding, how much gap to leave at trim, or how far siding sits from J-channel and corner posts. Those clearances are manufacturer-specified, and Section R703.11.1 makes the manufacturer's instructions the governing method for the siding and its accessories. Use the figures in the instructions for your product.
Can you install vinyl siding over foam board?
Yes, but when foam plastic sheathing is the only backing, the vinyl siding must carry a wind load design pressure rating that meets Table R703.11.2 (2021 IRC Section R703.11.2).
The same rule applies to insulated vinyl siding. Where vinyl siding is installed over foam, it must also comply with the rest of Section R703.11. Section R703.3.4 sends fastener length over foam to Section R703.11.2, and requires fasteners long enough to cover the foam thickness and still reach framing or sheathing as required.
When does the foam wind rating not apply?
Section R703.11.2 lists three exceptions, and in each case the siding is installed per Sections R703.3.3 and R703.11.1 or the manufacturer's instructions:
- The foam is applied directly over wood structural panels, fiberboard, gypsum sheathing or other approved backing that can independently resist the design wind pressure.
- The siding manufacturer's product specifications give an approved wind load design pressure rating for installation over foam plastic sheathing. That rating may be used, and the siding is installed per the manufacturer's instructions.
- The foam sheathing and its attachment have a design wind pressure resistance complying with Sections R316.8 and R301.2.1.
What wind pressure rating does Table R703.11.2 require?
The table gives the minimum adjusted design wind pressure (ASD, in psf) by ultimate design wind speed, exposure category, and whether the wall has interior gypsum wallboard.
2021 IRC Table R703.11.2, required minimum wind load design pressure rating for vinyl siding over foam plastic sheathing alone. Adjusted ASD pressure in psf. Case 1: with interior gypsum wallboard. Case 2: without.
| Ultimate design wind speed (mph) | Case 1, Exp. B | Case 1, Exp. C | Case 1, Exp. D | Case 2, Exp. B | Case 2, Exp. C | Case 2, Exp. D |
|---|---|---|---|---|---|---|
| 95 or less | -30.0 | -33.2 | -39.4 | -33.9 | -47.4 | -56.2 |
| 100 | -30.0 | -36.8 | -43.6 | -37.2 | -52.5 | -62.2 |
| 105 | -30.0 | -40.5 | -48.1 | -41.4 | -57.9 | -68.6 |
| 110 | -31.8 | -44.5 | -52.8 | -45.4 | -63.5 | -75.3 |
| 115 | -35.5 | -49.7 | -59.0 | -50.7 | -71.0 | -84.2 |
| 120 | -37.4 | -52.4 | -62.1 | -53.4 | -74.8 | -88.6 |
| 130 | -44.9 | -62.8 | -74.5 | -64.1 | -89.7 | -106 |
Above 130 mph, the table refers to its note d. Linear interpolation is permitted. The table values assume a maximum 30-foot mean roof height and an effective wind area of 10 square feet in Wall Zone 5 (corner). Note d also applies where foam is the only sheathing: the wall assembly must resist impact without puncture at least equivalent to a wood frame wall with minimum 7/16 inch OSB sheathing, tested to ASTM E1886.
Compare the table with the rating on the siding product's data sheet.
What does R703.15 say about cladding over foam?
Section R703.15 requires cladding over foam to follow Section R703, the manufacturer's approved instructions including any limits for use over foam, or an approved design. Tables R703.15.1 and R703.15.2 set fastening for cladding weight, but approved manufacturer instructions for use over foam take precedence (Exception 1). For vinyl siding, the wind rating and instructions above come first. Brick veneer is a different system: see brick ties.
Is insulated vinyl siding different?
Insulated vinyl siding must be certified and labeled to ASTM D7793 by an approved quality control agency, and it is installed with its accessories per the manufacturer's instructions (2021 IRC Section R703.13). It falls under the same foam sheathing wind rating rule in Section R703.11.2. Take the fastener length from the manufacturer, because foam backing adds thickness the nail has to cross.
Summary
The 2021 IRC requires labeled vinyl siding (ASTM D3679) installed per the manufacturer, with a 0.120 inch shank nail or 16-gage staple, at least 1-1/4 inches of total penetration, and maximum spacing of 16 inches for horizontal siding and 12 inches for vertical. Over foam plastic sheathing alone, the siding needs a wind rating that meets Table R703.11.2 unless an exception applies. Manufacturer instructions override the code defaults where the code says so, and local amendments govern.
Framing Plan is a preliminary drawing aid that draws joist layouts, beams and openings and exports PNG, PDF and DXF. It does not check siding or fasteners, so put the siding, barrier and fastener notes on your wall schedule yourself. Open the framing studio to lay out the framing behind the cladding. For the wall layout itself, see wall framing basics and, for plaster instead of vinyl, stucco lath.