Liquid vapor barriers are sprayed onto the exterior of a home to make it air and water tight.
Todd Detwiler Liquid vapor barriers are sprayed onto the exterior of a home to make it air and water tight.

Year after year, more builders are putting down their slap staplers and picking up rollers and sprayers in favor of liquid-applied air and moisture barriers, according to the Annual Builders Practice Survey from Home Innovation Research Labs. The most basic benefit is obvious: a singular monolithic coating that directly bonds to exterior wall sheathing without fasteners makes quick work of sealing a home from the elements. And while building science experts say the same results can be achieved with properly installed sheet-based barriers, home builders who’ve made the switch say they’ve discovered differences.

“Once you factor in all of the additional things you need to do for [sheet-based wraps], not to mention all of the holes you’re constantly putting in them, which you have to go back and fix, I’d say that the time and labor is about the same,” says David Schleicher, president of Prairie Design-Build in Lake Quivira, Kan. “But, in the end, the durability and confidence that we have in liquid-applied [barriers] is far greater.”

Carey Alcott, president of Mount Pleasant, S.C.–based William Carey Homes, says he finds liquid-applied barriers easier to visually inspect and, therefore, easier to trust. “I appreciate the fact that you can see that the building envelope is air and watertight,” he says. “You can’t do that with a standard house wrap.”

Alcott also says that, through blower-door tests, his company has discovered that liquid-applied barriers do a better job of sealing up the building envelope.

“I used to exclusively use spray foam insulation, not only for its R-value, but also to form an air-tight barrier,” Alcott says. “Air may have gotten into the walls through a housewrap, but it wasn’t going to penetrate the [closed-cell] foam to the inside environment. After the second house I did with [a liquid-applied product], I realized that all I need is thermal insulation,” which he says now often includes less expensive fiberglass batts.

That’s not to say liquid-applied products don’t come with any downsides. They do. Most notably, they’re more expensive. Liquids clock in anywhere from $1.88 to $3.38 more per square foot than sheet-based barriers. And though most liquid-applied products apply with a standard, heavy duty paint roller or a regular unpressurized sprayer, unlike sheet-based barriers, they also carry minimum temperature requirements. Manufacturers suggest a temperature of 40 F and above. (Rapid cure products that withstand colder temperatures are available, but cost extra.)

Liquid-applied barriers also require pre-treatment of the seams between sheathing with a seam sealer and, in some cases, a cloth mesh or tape. In cases where manufacturers offer a barrier as a complete system (including things like seam sealer, tapes and flashings), Peter Yost, vice president of technical services for building science publisher BuildingGreen, recommends going with the full package based on his company’s evaluations.