Metal roofing is tough, long-lasting, and low-maintenance — but only if it’s installed correctly. One of the most common (and expensive) mistakes people make is cranking down the screws way too hard. Here’s why that’s a bad idea and what actually happens when you do it.
1. You Crush the Rubber Washer
Most metal roofing screws come with a neoprene or EPDM washer that seals the hole and keeps water out. When you over-tighten, you squash that washer flat or even crack it. Once the rubber is deformed or damaged, it loses its ability to compress and seal properly. Water finds its way in, and you get leaks — often right above your living room ceiling.
2. You Dimple or Distort the Panel
Metal panels are designed to expand and contract with temperature changes. Over-driven screws create a “dimple” or oil-can effect around the fastener. This not only looks ugly, it also creates low spots where water and debris collect instead of shedding off the roof. Over time those dimples can turn into rust pits.
3. You Strip the Screw or the Panel
Keep turning after the washer is already compressed and you’ll either strip the threads in the purlin/underlayment or spin the screw right through the thin metal panel. Either way, the fastener loses holding power and the panel can loosen in wind — leading to more leaks and potential panel loss in a storm.
4. You Void the Warranty
Almost every metal roof manufacturer specifies “tighten until the washer just begins to bulge slightly” or “until rubber contacts the metal and is lightly compressed.” Over-tightening is considered improper installation and will void most paint, substrate, and weathertightness warranties. That 40-year warranty? Gone because someone used an impact driver like a torque monster.
The Right Way (It Takes 2 Seconds Longer)
- Use a screw gun with a depth-setting nose or (better yet) a proper torque-limiting clutch.
- Drive the screw until the washer just touches the metal and you see a very slight bulge in the rubber — no more.
- The panel should still be able to float slightly under the washer for thermal movement.
A good rule of thumb: if you can see the threads of the screw under the panel or the washer looks like a pancake, you went too far. Back it out and start over.
Taking those extra few seconds per screw saves you thousands in leak repairs, panel replacement, and interior damage later. Metal roofs last 50+ years when installed right — don’t sabotage yours with an overzealous trigger finger.
The WV Metal Promise
At WV Metal, we’re more than a roofing supplier—we’re your long-term partner in quality construction. From residential re-roofing to large-scale commercial installations, our West Virginia-based team combines local expertise with top-tier materials and craftsmanship to deliver results that endure.
Explore more at www.wvmetal.com and discover how we’re raising the standard for roofing excellence across homes, businesses, and communities statewide.
