8 Air Barrier Installation Tips for Commercial Construction

Thanks to their preset thickness and impressive ability to shield a building envelope, sheet-applied air and vapor barriers are a favorite of many commercial installers. They’re a much more durable option than low-budget weather-resistant barriers.

But that doesn’t mean you’re totally off the hook for hard work. Sheet air barrier installation takes a little more prep time and carefulness vs. liquid-applied barriers. (Learn how to install those here.) The little details matter, and can snowball into serious quality issues if you rush your work. 

Fortunately, with a little guidance, each step of the installation process is very doable, even if you’re fairly new to this construction product.

Air Barrier Installation, Step by Step

There are do's and don't’s for every step of the air barrier installation process: 

1. Get the right tools. 
2. Check your surroundings – before and after installation. 
3. Prep the surface. 
4. Cut and measure and cut. 
5. Start from the bottom. 
6. Attach the barrier. 
7. Seal seams and penetrations. 
8. Inspect your work. 

As always, a successful construction job starts with setting yourself up for success.

(Related Resource: How to Install Foam Expansion Joints)

STEP #1: Get the right tools.

Ready to work? In addition to the air barrier membranes themselves, you may need:

Most, but not all, sheet membrane installation products require you to prime the sheathing. A primer makes the base more uniform and stable, reducing the risk of air leaks through gaps or poorly adhered sections. Most primers for self-adhered barriers come in roll-on form, but if you’re fully in fire-drill mode, track down a spray-on primer to speed up installation.

When you’re ready to cut the sheets themselves, a utility knife is a handy tool for getting clean, precise cuts in tough places. Some subcontractors use scissors if the material is especially thin or flexible.

Later in the project, a two-handed roller is a godsend. This tool will help you ensure 100% of the membrane attaches to the wall.

STEP #2: Check your surroundings – before and during installation.

Before lining up labor, tools, and a schedule, make sure the environment looks conducive to the material you're using. Actually, your environment matters both in the lead-up phase and the installation date.

In the days leading up to installation, find acceptable storage conditions for your air barrier materials. Liquid-applied products are prone to job-site damage from:

• Direct sunlight – causes brittleness
• Moisture – causes loss of adhesion
• Extreme heat – can soften and warp some materials
• Wind – can tear or blow them away
• Debris – dirt & dust on the surface can hamper adhesion

Even on installation day, don’t drag the products out first thing in the morning and leave them naked and alone for several hours. Cover them up.

When the time to get to work is near, check the area’s:

• Temperature
• Humidity
• Dew point
• Surface dampness 

One sheet barrier installation may have a different safe temperature range vs. another product. (Interestingly, it’s actually the detail sealant and any primer you use that limit the range, rather than the sheet itself.) Most sheet materials tempered indoors are safe to use as long as it’s 12°F or higher outside. You can go lower if you’re using a special low-temp product with a tackier adhesive.

All products come with manufacturer guidelines to ideal day-of conditions. A distributor with technical expertise can also answer any concerns leading up to the installation.

STEP #3: Prep the surface.

By spending a little extra time prepping the sheathing base now, you’ll help the barrier adhere and seal against the surface much, much later.

Many sheet products require a primer or adhesive to make the bond stronger. Primers are doubly important when the sheathing surface is porous, dusty, or otherwise tricky to bond to.

Whether you use a primer or not, the substrate isn’t ready for installation until it’s:

• Clean
• Dry
• Smooth

It doesn’t have to look like silk curtains, but the working surface must be at least somewhat smooth for the primer and barrier to stick. This may require sanding or other treatments to eliminate sharp edges and mortar droppings.

STEP #4: Measure and cut.

Accurately measure the space where the barrier will be installed. Sheathing of any kind should have:

• Tight joints between sheets
• Full coverage at outside corners, preventing recessed, “inside corner” appearances
• No broken edges

When you’re certain you’re ready, cut the material to size. Use appropriate techniques to cut the material without damaging it, keeping in mind the material type and thickness. Allow for some overlap at the seams to ensure a continuous barrier. 

If your detail sheets aren’t preformed, you’ll need to cut them now too. 

STEP #5: Start from the bottom.

If your primer is dry, or you used no primer, it’s time to address the air barrier itself.

Starting from the bottom of the substrate ensures that overlapping layers shed water correctly and prevent moisture from trapping between layers or penetrating the barrier.

Sheet barrier installation requires roll pressing the product into place. If not, “fishmouthing” (poor adhesion) and unwanted overlaps might occur. Apply the lowest sheets first, working your way up the wall or across the floor. Set each piece over the one below it to create proper drainage and prevent water intrusion.

STEP #6: Attach the barrier.

Securing the sheet barrier to the structure is essential to performance and service life as the product itself.

Think it through. The alignment and spacing of materials will determine whether they work correctly and merge seamlessly with other building components. 

For sheet-applied barriers, the fastening method depends on the specific product. On the cheaper end, It could be:

• Staples
• Nails
• Screws

A higher-quality product is almost always self-adhering.

Use the attachment method the barrier manufacturer recommends. Fasteners should be flush with the sheathing. Cover the fasteners with tape or sealant to keep the barrier fully intact.

As you install the air barriers:

• Keep them tight to the substrate
• Avoid wrinkles or bridging in corners
• Keep asphalt edges 0.5” back from the exterior’s finish

Don’t stop rolling until every square inch of the sheet is on the surface!

STEP #7: Seal seams and penetrations.

Proper sealing at this stage keeps the integrity of the air barrier intact – otherwise, what’s the point?

Contractors attach sheathing to the framework first to give the air barrier a solid and continuous home. If the installation is vertical, make sure that neighboring sheets are lapped tightly as you place them on the sheathing. 

Naturally, you’ll be looking at seams and penetrations as potential trouble sites:

• Seams/gaps: Use manufacturer-recommended tape or sealants to overlap and seal all seams. For sheet-applied barriers, ensure overlaps are generous (typically 3-12”) and sealed with tape designed for vapor barriers. As long as the sheathing’s gaps are less than 0.5” wide, there’s no need to seal them.
  
  
• Penetrations: Detail sheets usually go up first. Use them at rough window openings and areas where pipes, lines, and other utilities penetrate the building. Extend the sheet into any door or window openings, past the thermal transition.

Any area you fail to secure could create an opening for moisture and air to rush in. 

STEP #8: Inspect your work.

You’re not ready to hit the Wendy’s drive-thru just yet. Before you say “mission accomplished,” closely inspect the sheet air barrier. 

Check for any:

• Tears
• Gaps
• Poorly sealed seams 

Use the appropriate tape or sealant to make repairs immediately.

Note the emphasis on “immediately” – swift action is key to maintaining the barrier’s effectiveness. Regular inspections during construction and after any significant repairs to the building envelope will help your work last longer.

Training for Air & Vapor Barrier Installation

Sheet-applied air and vapor barriers take a little extra work and diligence, but in many commercial construction projects, they’re worth it. Plan ahead, take your time, and check your work – it’s better to nail it now than hear from an angry property owner later.

If product installation is still tripping you up, seek out the manufacturer or distributor. We offer a suite of training services for contractors working with a new material or project type: