It’s Time to Switch to Cap Fasteners
Gone are the days of hammer tackers for installing housewrap and roof underlayment.
Synopsis: Once upon a time, a hammer tacker was the best tool for attaching housewrap and roof underlayment to house sheathing. Now, according to builder Mike Guertin, it’s time to switch to cap fasteners. These tools are not only more effective but also are what you need to comply with manufacturer instructions and building codes. Caps are 1-in-dia. or larger plastic or metal disks fastened with nails or staples. The cap increases the fastener’s surface area, meaning less chance for tearing even under windy conditions or foot traffic. Pneumatic cap staplers are available in two styles: tools that attach lighter weight 20- and 21-ga. staples; and tools that attach 18-ga. staples, which have more holding power. Pneumatic cap nailers also are available. Additionally, National Nail makes a hammer tacker that has a manual cap-feed trigger.
Hammer tackers, the tools used to fasten the membrane you’re counting on to back up your siding or roofing, are obsolete. They don’t meet most house wrap and underlayment manufacturers’ instructions and, by extension, don’t comply with building codes. If this is news to you, you aren’t alone.
When I talk with building pros about the now-fading era of hammer tackers, they often respond with skepticism. They claim they’ve used hammer tackers for X number of years without a problem, or they point out that everyone else uses them. Unfortunately, most installers are not aware that cap fasteners — 1-in.-dia. or larger plastic or metal disks fastened with nails or staples — are a more effective alternative.
In fact, of the 52 synthetic-roof underlayment and house wrap installation instructions I recently researched, 43 called for a minimum 1-in.-dia. cap-type fastener. And starting with the 2012 IRC, cap nails are required for fastening roof underlayment in high-wind areas. Have I hung up my hammer tacker? No, but I use it now only to drive enough staples to hold material in place, making sure always to place fasteners where they will be covered.
I suspect that aside from extra cost or just not realizing that hammer tackers are a problem, builders are slow to switch to cap fasteners because the options can be confusing.
The case for caps is strong
Caps hold the house wrap and the underlayment better than staples, they reduce the chance for tears in windy conditions, and they protect the membrane from the nose of the fastener installation tool.
Hammer tackers can cut through house wrap and underlayments when you whack the steel nose against wall or roof sheathing. Synthetic underlayments and house wraps are generally tougher than the tar paper and building paper they replace, but they are still vulnerable to punctures, tears, and stretching around the staple legs.
Although the resulting holes are small, they will leak — and that’s the rub. Many common building materials and building systems today are less forgiving of moisture than those used 50 or more years ago. Even vapor-permeable house wraps may not diffuse moisture that leaks in through holes fast enough to keep rot at bay.
It’s not just leaks, though. Most manufacturers have tested their synthetic underlayments to see what it takes to keep sheets in place and safe to walk on. The thin, narrow-crown staples used in a hammer tacker easily tear through the materials, especially under windy conditions.
And one last thing that raises the bar for professionals: Insurance underwriters often deny claims when negligent work is the root of the problem. When an installer disregards house wrap and roof-underlayment manufacturers’ explicit instructions, the insurance company may not mop up the mess.
Tools come in a few flavors
Installing cap nails by hand is the most accurate approach. It’s slow going, though, and nails preloaded with caps are bulky. There’s a limit to how many fit in a nail pouch. Collated caps and fasteners automatically feed to the nose of a tool, so all you have to do is pull the trigger.
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Editor’s Note:
Some of the cap tools in the article have been updated and improved, some have been discontinued, and there are new models on the market.
Here’s a mostly-complete list of what’s on the market in 2020:
From FineHomebuilding #224
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