How To Properly Fasten Rigid Foam Board Insulation


Are you wondering what’s the most effective pattern for fastening Halo Exterra foam board insulation? Well, it depends on the substrate to which you’re attaching the boards — wood sheathing, open stud assemblies, and prefabricated walls all have different recommended nailing patterns.

In this guide, we’ll try to simplify the common nailing patterns for fastening non-structural Halo Exterra panels to these different substrate types. Read on to learn more!

Recommended Patterns for Fastening Exterra Panels to Wood Sheathing

The recommended nailing pattern is quite simple, and applies regardless of the boards’ orientation (i.e. it works for vertical and horizontal placement).

Lengthwise, you’ll want to locate the fasteners at 45 inches on center; this way, there’s a 3-inch space between the edge of the panel and the first fastener, and the center fastener is placed dead in the center of the board. You’ll have a total of 3 fasteners on each long side of the panel.

Widthwise, there are 2 fasteners, both offset 3 inches from the edge of the panel. This way, there’s a distance of 42 inches between the fasteners.


Typical Nailing Patterns Over Wood Sheathing

Tips for Nailing Exterra Boards to Sheathing

You can follow the patterns and our tips below when you’re fastening Exterra panels to wood sheathing.

1.    Seal Joints with Sheathing Tape

Halo’s Exterra provides an effective water-resistive barrier; however, to maintain this barrier after the panels are installed, you’ll have to seal all the joints between the panels. Sheathing tape works great for this purpose, although you’ll have to fill any large gaps with spray foam, too.

2.    No Need to Drive Fasteners to Studs When Installing on Sheathing

If you’re hanging the Exterra boards onto sheathing, there’s no need to drive the fasteners into the wood studs beyond — the sheathing itself will serve as a sufficient backing. This way, you can do away with shorter fasteners and your fastening patterns won’t be tethered to stud locations.

3.    Stagger Joints to Minimize Air Gaps

Whether you’re installing Exterra panels horizontally or vertically, you technically don’t need to worry about staggering the vertical joints in a running bond pattern. However, we’d advise you to do so anyway because offsetting Exterra and sheathing joints will help you reduce air gaps and improve the assembly’s air tightness.

Offset Joints Between Exterra and Wood Sheathing

Recommended Patterns for Fastening Exterra Directly to Wooden Studs

Regardless of stud spacing, you’ll want to position the vertical edges of the Exterra ¾ inches from the edge of the stud. Next, you’ll locate the outermost fasteners as close to the inside edge of the outermost studs:

Meanwhile, the fasteners in the middle should be nailed to the center of each of the innermost studs; these are only required along the edge of the Exterra boards, not in the middle.

16 Inches On Center

When the studs are placed at 16 inches on center, the distance between the outer and inner fasteners should be 15 ¼ inches, while the two inner fasteners should be nailed 16 inches apart. As you can see, fasteners placed vertically are spaced 22½ inches on center, with the first fastener going in 3 inches from the top and bottom edges of the panels. 

Stagger Fasteners

With 16-inch stud spacing, you should stagger the fasteners at the joints between Exterra panels:

24 Inches on Center

With a 24-inch on center stud placement, the distance between the outermost and the inner stud fasteners will be 23¼ inches, while inner stud fasteners should be 24 inches apart. Again, fasteners are staggered at joints between Exterra panels:

24 Inch Wall Pattern

Note that with horizontal Exterra placement, there’s no need to stagger fasteners at the panels’ joints. Fasteners that are nailed in vertically are spaced 21 inches on center, with a 6-inch gap at the panel joints:

Horizontal Panel Placement

Tips for Nailing Exterra Boards to Wooden Studs

Below are a few key tips you should follow when nailing Exterra boards directly to wooden studs.

1.    Brace the Studs in Compliance With Local Codes

Note that Exterra boards aren’t structural, so you’ll still have to brace the studs according to your local code requirements.


2.    Any Orientation Will Do

Whether you choose to install the Exterra panels horizontally or vertically is entirely up to you. Both orientations are acceptable and don’t change much in terms of Exterra’s effectiveness.

3.    Rest Vertical Joints at Least Halfway On the Stud

To make sure that the Exterra panels rest either fully, or at least halfway on the stud. The minimum distance from the edge of the overlapping panel to the edge of the stud should be ¾ of an inch.

Recommended Patterns For Fastening Halo Exterra to Prefabricated Wall Assemblies

If you’re nailing Exterra panels to prefabricated wall assemblies, the fastener patterns are similar to those in open stud walls. One notable distinction is that with prefabricated assemblies, Exterra panels require a bit more support to stay intact during transport; this is achieved by nailing the boards to the middle studs as well as the edge studs:

Fastening Halo Exterra to Prefabricated Wall Assemblies

Wrapping It Up

We hope that this guide to Exterra nailing patterns will come in handy in the field! If you’d like to flip through the complete fastening instructions, you can get the document by following the link here.

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